Dave, KVL doesn't hold under a varying magnetic field.
Dave, KVL doesn't hold under a varying magnetic field.
Really?
So according to the statement, AC circuits (with transformers and such) can not be solved using KVL!
You better go tell the whole electric power industry that they have been analyzing circuits under the effects of magnetic fields incorrectly for the last 160 years!!!
I think Lewins model on which he applied KVL was incorrect. The lines in a circuit diagram don't interact with a magnetic field.
If you watch the original lecture, the error creeps in when he assumes "A1=A2" and "D1=D2", but this just doesn't hold.
brilliantly debunked by Lewin.
I think Lewins model on which he applied KVL was incorrect. The lines in a circuit diagram don't interact with a magnetic field.
If you watch the original lecture, the error creeps in when he assumes "A1=A2" and "D1=D2", but this just doesn't hold.
Now Lewin doesn't know how to apply Kirchhoff's law to a circuit, and, worse, doesn't know how to draw diagrams.
Precisely. You cannot on one hand assume those "wires" in the circuit be "ideal" and effectively form one "node", and at the same time expect them to span up a area for the magnetic flux to pass through. It doesn't work that way. These circuit lines are dimensionless. They have zero length. The area is zero, therefore, and no magnetic flux passing through them. Besides, KVL is a mere calculation tool for network analysis. If your result doesn't match the measurements, clearly something is wrong with the model. But not with the method as such. That's a bit like blaming spice for not matching reality when you forgot to put an element.
QuoteYou better go tell the whole electric power industry that they have been analyzing circuits under the effects of magnetic fields incorrectly for the last 160 years!!!I don't need to. The whole power electric industry never made the mistake of analyzing a circuit under a varying magnetic field using KVL. In fact the whole power electric industry started out because of Faraday's discoveries which was solely explained by Maxwell's equations. And that's what we use to this very day.
That's precisely your, Mehdi's, Dave's and everybody-else-that-insist-that-KVL-always-hold's mistake.
KVL says that the voltages measured along the path of a mesh add up to zero.
But Lewin showed at least one circuit where the voltages do not add up to zero.
You cannot solve such circuit using KVL. It is impossible. You'll have to resort to the full monty and use Maxwell's equations at least to calculate the EMF produced by the varying magnetic field.
After that, you can of course devise an equivalent circuit where instead of a varying magnetic field producing the extra EMF upon the entire circuit, you have a battery, a generator, a transformer, or any other equivalent lumped (i.e. localized) component to produce the same EMF and get the exact same effect on the other components. In that case, you can solve the equivalent circuit using KVL because you theoretically removed the varying field from the circuit and stashed it away in the equivalent component.
But that is just a theoretical trick that has a lot of caveats.
So how's that possible? How can we have, so to speak, a spooky "component" that produces an EMF in a circuit, but is not present there? This seems to violate the principle of conservation of energy, doesn't it? Those are legit questions. But to answer them you need to abandon KVL, which these people are not prepared to accept. To reconcile their cognitive bias with the real phenomenon that contradicts it, they create all the irrational arguments I listed above and more.
So how's that possible? How can we have, so to speak, a spooky "component" that produces an EMF in a circuit, but is not present there? This seems to violate the principle of conservation of energy, doesn't it? Those are legit questions. But to answer them you need to abandon KVL, which these people are not prepared to accept. To reconcile their cognitive bias with the real phenomenon that contradicts it, they create all the irrational arguments I listed above and more.
That's exactly your problem. There cannot be a "spooky component" that is not present but causes an effect. You have to have it in your model, otherwise all calculations are nonsense. Yes, you cannot calculate current induced by magnetic flux with KVL, yes you need to solve the Maxwell-Faraday equation to calculate the EMF, but after you've done that, you cannot simply forget about it and omit if from your circuit and postulate: "current flows in this circuit but without anything that causes it".
Right there is proof that you have no idea of what you are talking about! If (and that is a big IF) you are an electrical/electronics engineer, you are embarrassing yourself. If your background is in physics, then I know were you are coming from, and your ignorance is understandable.
bsfeechannel understanding of KVL is stuck in 1845.
Right there is proof that you have no idea of what you are talking about! If (and that is a big IF) you are an electrical/electronics engineer, you are embarrassing yourself. If your background is in physics, then I know were you are coming from, and your ignorance is understandable.
Ah the ad hominem argument. Let's add it to the list above.
KVL always holds because in the eyes of EEVBlog forum member jesuscf, EEVBlog member bsfeechannel is perhaps not an engineer, but probably a physicist.
But Lewin showed at least one circuit where the voltages do not add up to zero.Only because he omitted a critical element of the circuit.
His diagram was simply incomplete: he drew a line in the diagram and then promptly neglected that it's a real, physical wire and not an ideal "net" you would find in a schematic.
And that is exactly the error that Dr. Lewin made: He drew up a circuit, but it was not the equivalent of his experiment and then tried to solve that with KVL, and of course it failed.
Solving an equivalent circuit is not a theoretical trick, it is exactly how network analysis works. How do you calculate a circuit that has a BJT in it? With an equivalent circuit using e.g. the Ebers-Moll transistor model.
That's exactly your problem. There cannot be a "spooky component" that is not present but causes an effect.
You have to have it in your model, otherwise all calculations are nonsense.
Yes, you cannot calculate current induced by magnetic flux with KVL, yes you need to solve the Maxwell-Faraday equation to calculate the EMF,
but after you've done that, you cannot simply forget about it and omit if from your circuit and postulate: "current flows in this circuit but without anything that causes it".
Hey bsfeechannel, I am honestly curious about your credentials.
Are you an electrical/electronics engineer with a degree from a university (or similar) or not?
I'll need you to prove it by solving "problem #24" from your hero Dr. Lewin, but as an electrical/electronics engineer will do:
You do not expect to find two diodes and two current sources inside a transistor, do you?
The circuit had just two resistors and nothing else. And his model predicted exactly what happened in practice. KVL failed on the board. And then failed on the bench.
Hey bsfeechannel, I am honestly curious about your credentials.
Thank you for your interest in my credentials.QuoteAre you an electrical/electronics engineer with a degree from a university (or similar) or not?
I think that's irrelevant for the present discussion.QuoteI'll need you to prove it by solving "problem #24" from your hero Dr. Lewin, but as an electrical/electronics engineer will do:
Lewin is not my "hero". I don't subscribe to his channel, nor follow him anywhere on the social networks.
He just happened to show a physical phenomenon whose understanding is very important for electronics engineering.
And for whoever posted the 5-resistor video, maybe I've misunderstood, but I seem to see another glaring error regarding the supposed symmetry of the current between the L-lower and R-upper resistors regardless of the resistance. Try 0R for the right upper one and see if that holds!
As a practical matter, if there are two different voltages between the two points depending on which branch you follow, how do the oscilloscopes 'know' which branch they are measuring?
Is that determined by where they are physically placed?
Are they briefed beforehand?
If you want to debate, correct or wrangle about anything I've said, please answer this question first as I have no desire to argue this issue until that is cleared up.
And as a theoretical matter, the voltage between two points can never be 'path dependent', that's ridiculous. Voltage is at its core an absolute value, we just typically use and measure relative values because, well, circuits and current.
Now as for KVL and magnetic fields, you can all have at it, but there's one thing I haven't seen mentioned, so someone point it out if I've missed it: Change in flux through a loop causes EMF, EMF causes current to flow, that current then causes......counter EMF? No?
Anyway, connecting two test instruments to different points on a wire with current flowing in it and in a changing magnetic field and then claiming they are connected to the 'same' point makes me not want to try to solve the problem.
I just have to ask: do you fundamentally understand the Maxwell-Faraday Equation? I have my doubts. Otherwise you would not claim that the circuit consists of only two resistors connected by wires that can be seen as "dead shorts" and will have no voltage across them.
Do you agree that the Maxwell-Faraday equation relates a time varying magnetic flux to an electric field? Do you agree that this changing flux _causes_ an electric field in the wire? Do you agree that an electric field is a difference in potential? Do you agree that a potential difference is measurable as a voltage between the wire ends?
This is very much how a transformer works.
If you agree on all this, then you should be able to see that Dr. Lewins circuit is not just two resistors. It is in fact a transformer (or maybe generator) with the single secondary winding cut open in two places to insert resistors.
And it is the voltage across those two wire that you need to take into account when you add up all the voltages in the loop.
OK. So let's suppose that the wires in Lewin's circuit have a 0.1 ohm resistance. R1=100 Ω and R2=900 Ω. So, around the loop, we will have 100 + 900 + 0.1 + 0.1 = 1000.2 ohms. Now let's suppose that the EMF generated by the varying magnetic field induces a current of, say, 1mA. Multiplying that current by the resistance of each wire (0.1 Ω) will give us 100 µV on them. The voltage on R1 will be 100 mV, while on R2 we will have 900 mV. Adding all voltages up, we will have 1.0002 V. So there you have it. The voltages around the loop will still not be adding up to zero.
I started writing a detailed response. But I think I let the posts of @bsfeechannel just stand on their own. I mean, just look at the calculations.
I conclude as follows: :wtf: :palm: and will now stop |O.
Have a nice day.
Yes. That's why we study vector calculus at any engineering graduation course before we study electromagnetism. Because to understand this bleep you need to think "fourth-dimentionally". I.e. you need to understand that electricity and magnetism are not phenomena confined to electronic components, and how this thing behave in space.
So, frame of references, relative positions, relative velocities, paths, rates of change. All of that counts.
The oscilloscopes "know" what branch they are measuring because they form a loop with each resistor. If you pause Lewin's presentation on Youtube ( /watch?v=nGQbA2jwkWI ) at 41:54, you'll see that the scope on the right forms a loop with R2. In that loop, there's no varying magnetic field. So, all the voltages will add up to zero according to Faraday's law and, in this case, to KVL, which is nothing more than a special case of Faraday's law when you have no varying magnetic field inside the path of the circuit. So the voltage on the right scope will have to be exactly the voltage on R2.
Voltage can be path dependent if you are dealing with a non conservative electric field (i.e. one generated by a varying magnetic field).
Since the wires have very low resistance compared to the resistors, they can be considered practically dead shorts.
Yes I did and they still do not add up to zero.
BS must be pointed out and identified every time it shows up!
Please, don't say "a current is induced". Maxwell-Faraday clearly tells us that there is an electric field resulting from the changing magnetic flux. Current is what results out of Ohms law.
That's three lines of blather that doesn't answer my question.
You're telling me that the display of my oscilloscope depends on not only how I connect it, but where I physically place it.
Although that may be true at some very minor level due to interference and other effects, it is nonsense here.
Suppose I had long cables on the two scopes and swapped their physical positions left and right, well out of reach of any magnetic field from the experiment. Now they read the other way?
How about if I take the leads out perpendicularly and use two channels of one scope?
How about if I just use one scope?
These are just simple thought experiments that seem to me to reduce the experiment as claimed to an absurdity. I know some people have looked at this experimentally and I have no comment on those arguments because I haven't looked at them closely.
OK, if you are depending on the physical layout of the test leads, rather than the ultimate location of the oscilloscope (a much less ridiculous choice) than you need to reexamine the statement that there is no flux through that outer loop.
In order for the solenoid to induce a current in the loop, there has to be a net flux change inside the loop, but those flux lines have to eventually wrap around and go back to their opposite pole. If they do that inside the loop, then they cancel out the net flux. If they do that anywhere outside the loop, then your 'no varying magnetic field in the loop' becomes very questionable and would need to be measured by making another loop as physically close as possible but with a separate resistor not connected to the inner loop.
Now if you look at how most actual voltage measuring instruments work, whether they are an analog meter or oscilloscope, they measure the difference in absolute potential across their two input terminals. They can do this either by reacting to electric fields directly or by allowing a small amount of current to flow. In other words, the ideal voltmeter, however it works, reacts just like my hypothetical electrometer pair. The voltmeter doesn't actually care about path dependence or anything else in the DUT, just about the potentials presented at its inputs. It just measures the difference between two scalar quantities.
Since this a time-variant system, the wires also have inductance. I suspect that both the inductance and resistance are low enough in this case that they don't matter, but without numbers I can't say. I think we can agree that the oscilloscopes read what they do because they are reading more or less the voltage drop across each resistor that results from the induced current. Without examining Lewin's apparatus or experimenting myself, I couldn't say exactly how that was achieved. A lot of the attempted explanations and experiments that have been shown regarding this seem as flawed as the original, but I'm pretty sure the answer is simply that there is another layer or two of complexity beyond the simple path-dependence that Lewin was demonstrating.
Wow. The argument that never dies.
There (at least) two ways of modeling this:
Maxwell's equations model the electric and magnetic vector fields at every point in space.
Circuit theory uses a lumped circuit to model the voltages and currents. KVL and KCL always hold in lumped circuit models.
Here are some great videos that explain it all:
I started writing a detailed response. But I think I let the posts of @bsfeechannel just stand on their own. I mean, just look at the calculations.
But when electroboom did the experiment he accounted for many of this things... and KVL worked as expected:
One more thing: bsfeechannel, I called you out and you didn't deliver.
You have no idea of what you are talking about. Talking to you is exactly like talking to a flat earther or an antivaxer. So I decided to go thunderf00t on you call out all your BS.
But when electroboom did the experiment he accounted for many of this things... and KVL worked as expected:
Nope. Lewin used the theory to predict that the two resistors would have different voltages. Mehdi' experiment showed that Lewin's prediction was right. Mehdi admitted that explicitly.
Then Mehdi said that although the experiment matched exactly what Lewin predicted, he, Mehdi, thought that Lewin's was wrong.
This is a case of doublethink, where someone simultaneously accepts two mutually contradictory beliefs as correct, often in contravention to one's own sense of reality.QuoteOne more thing: bsfeechannel, I called you out and you didn't deliver.
Not interested in your piss contest.QuoteYou have no idea of what you are talking about. Talking to you is exactly like talking to a flat earther or an antivaxer. So I decided to go thunderf00t on you call out all your BS.
Be my guest.
For everyone else reading, who are you going to trust? Electroboom whom uses multiple oscilloscopes in a regular basis or Lewin that had no idea on what is going on with the oscilloscope and often calls it a voltmeter?
For everyone else reading, who are you going to trust? Electroboom whom uses multiple oscilloscopes in a regular basis or Lewin that had no idea on what is going on with the oscilloscope and often calls it a voltmeter?
Maybe lighten up a bit? An oscilloscope IS a voltmeter! And 'trust' isn't the issue, I'm (maybe) interested in what is going on, not comparing the trustworthiness of two rather flamboyant showmen.
Very pertinent question. Lewin took that precaution and demonstrated both theoretically and experimentally that the magnetic field outside the solenoid, where its length is much grater than its diameter, is negligible. See his lecture about it [ https://youtu.be/MXuZ1SRjpqk ]. So, from a practical point of view, the field outside the solenoid can be considered zero.
You are assuming your meter doesn't care about path dependence, but numerous experiments show otherwise. In Lewin's experiment, R1 and R2 are subject to electric fields of different intensities (assuming the resistors have the same size). And they can even be calculated. That's why the meters are showing different voltages (assuming there's no varying magnetic field in the loop made by the meter, the probes and the DUT).
If R1 and R2 were connected in parallel and attached to a battery, the voltages would be the same no matter what, because they would be subject to electric fields of the same intensity.
Stop for a moment and think. The voltages between points A and D in Lewin's experiment cannot be the same for the two resistors, otherwise they would have different currents flowing through them, which is impossible.
NO! Charlatans like bsfeechannel must be confronted.
It seems fairly clear to me, and it seems to be fairly explicitly admitted in the second video from MIT (perhaps where Lewin got the idea) posted by rfeecs that the 'path dependence' vis a vis the voltmeters is not the path within the loop, but rather the positioning of the test leads going to the voltmeter.
As far as positioning the scope, imagine a two-channel scope positioned well above the apparatus, not to the R1 or R2 side but right between them, far enough away that any electric or magnetic field is truly negligible. Now everything is identical except the test leads going to the apparatus and their position is the only variable.
As for the rest of the issues and whether the voltages at the resistors must equal the voltage at the test points simply because wires are 'dead shorts' is something that I think involves--as I said previously--another layer of complexity.
'Voltage ambiguity' isn't really a workable concept, thus much of the consternation among the people trying (and mostly failing!) to explain this.
One thing to consider is your repeated assertion that you can't have a voltage differential in the wires because they have low resistance. So are there any conditions where that statement is not true? Are there conditions where a straight piece of wire will have a voltage differential from end-to-end?
QuoteOne thing to consider is your repeated assertion that you can't have a voltage differential in the wires because they have low resistance. So are there any conditions where that statement is not true? Are there conditions where a straight piece of wire will have a voltage differential from end-to-end?
Yes. When the wires are moving perpendicular to the magnetic field.
But in Lewin's circuit the wires are static in relation to the frame of reference. So the voltage across the wires will obey ohms law.
One misconception is that since the secondary of a transformer is just a wire, and I can measure a voltage when I attach a meter to the terminals, it is the wire that is generating the voltage.
What the wire is doing is to set a boundary condition around the loop where the rotational electric field will be forbidden to exist. This will concentrate the field between the terminals. What you are measuring is a voltage produced by an electric field that only exists between the terminals. It doesn't exist in the wire. So it cannot produce a voltage across it.
When you attach a load to the secondary and current flows, then you'll have an electric field inside the wire that will produce a voltage which will be proportional the current times the resistance of the wire. This electric field will have to be discounted from the field at the terminals, because the integral of the field around the loop is proportional to the derivative of the magnetic field ( I.e. the field in the wire plus the field in the load must add up to the induced EMF no matter what).
This is plain nonsense. It doesn't matter if the wires are moving or not. You will have a voltage whenever the magnetic flux changes. There is no term in the Maxwell-Faraday equation that has any component of spatial displacement.
But if there is no field "in the wire", how does a Variac work? Or any tapped transformer? Surely the voltage at the tap cannot be due to Ohms law if there's no current flowing? And if you connect the outer terminals of the transformer to a load, does that mean the field inside the wire collapses? Then the voltage at the tap would also collapse. But quite obviously, this isn't the case.
See above to understand why this cannot be a proper explanation.
A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn.
A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn.
WHAT! This quote needs to be preserved for posterity! :-DD
What the wire is doing is to set a boundary condition around the loop where the rotational electric field will be forbidden to exist. This will concentrate the field between the terminals. What you are measuring is a voltage produced by an electric field that only exists between the terminals. It doesn't exist in the wire. So it cannot produce a voltage across it.
Yeah, it's getting more and more interesting with each new post.
Now only Lorentz' force creates an electric field
but not a changing magnetic flux (despite Maxwell-Faraday telling the opposite),
and now you only have an electric field in the space between the transformer windings.
I really wonder how antennas ever worked.
Besides, this contradicts his own statement:
If the field "concentrates between the terminals" it should be nowhere else. Not between the windings either, because clearly they are connected to each other and thus there should not be a "boundary condition" where the "rotational electric field" (what?) is "forbidden to exist".
Next argument will be that the field only exists when you connect a meter to measure it, which would violate causality.
Yes. When the wires are moving perpendicular to the magnetic field.
But in Lewin's circuit the wires are static in relation to the frame of reference. So the voltage across the wires will obey ohms law.
KVL and KCL are special cases of the Maxwell's equations with some assumptions.
Maxwell's equations always hold, if we assume if there is no quantum physics shenanigans.
KVL always hold, if we assume a few things. How to derive it, what to assume? Google it, or open your university books, because in every half decent university they teach this shit, and I am amazed that people still talk about this. I am not surprised if a physics professor in some US university would go ahead and "discover on his own" that KVL suddenly doesn't hold. What I'm amazed that they let this professor teach electronics to students, and had nobody around tell him that "Da! It is in the coursework for the engineers, haven't you read it?"
I got tired of pointing out the literature on the debated subject and be dismissed out of hand by un-educated blockheads.
I got tired of pointing out the literature on the debated subject and be dismissed out of hand by un-educated blockheads.
You got tired because you don't understand the theory and you dismiss the evidence that contradicts your claims.
Let me summarize the discussion for you:
I trust Mehdi. Lewin is full of BS and everyone that shows any practical evidence that Mehdi's claims are false and Lewin's claim correspond to reality is a blockhead.
Only irrational arguments. No scientific or engineering arguments and no evidence.
You contribute nothing to any discussion.
Once again... Says the person with no credentials that dropped this jewel:
"A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn."
Once again... Says the person with no credentials that dropped this jewel:
"A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn."
Well, but that is true.
You can read and learn, if you want.
http://web.mit.edu/6.013_book/www/chapter10/10.1.html (http://web.mit.edu/6.013_book/www/chapter10/10.1.html)
You can read and learn, if you want.
http://web.mit.edu/6.013_book/www/chapter10/10.1.html (http://web.mit.edu/6.013_book/www/chapter10/10.1.html)
So if there is only one loop, no electric field?
Once again... Says the person with no credentials that dropped this jewel:
"A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn."
He doesn't know that the voltage is produced in the gap between the terminals. Typical KVLer, who thinks there must be some kind of battery inside the wire pulling the charges along.
A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn.
Once again... Says the person with no credentials that dropped this jewel:
"A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn."
Well, but that is true.
You can read and learn, if you want.
http://web.mit.edu/6.013_book/www/chapter10/10.1.html (http://web.mit.edu/6.013_book/www/chapter10/10.1.html)
So which one is the correct one? This one?He doesn't know that the voltage is produced in the gap between the terminals. Typical KVLer, who thinks there must be some kind of battery inside the wire pulling the charges along.
Or this one?A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn.
I hope one day we have perfect conductors!
That's a lot of stuff to digest. But one aspect seems obvious, no matter which "cult" you adhere to: In order to actually observe the path dependence of the voltage between A and D, you need to probe in a way that allows "selecting" the path you want to observe.
Watching the MIT video that was linked here by @rfeecs, it is obvious that this selection is done only by the layout of the probe wires. If I understood the reasoning correctly, the selector is not the magnetic flux, because the paths that lead to the instrument are outside of it.
That means the chosen path must never encompass any area that is inside the magnetic flux.
What I still have a hard time coming to terms with is that there is no voltage contribution by the other possible path through the second resistor
Now, why is there no voltage contribution by the wire itself, this is the most counter-intuitive aspect and the core of the claim that KVL doesn't hold. "Silicon Soup" explains that the rotational electric field caused by the changing magnetic flux and the electric field inside the wire caused by charge separation cancel each other out and the net electric field "in the wire" is 0. D'oh! So it's there but you cannot observe it because there's another electric field of same "strength" just in the "opposite direction". I put that in quotes not to express doubt but to denote that I understand that it's a simplification and we're talking about vectors here. But it is still hard to stomach because you can observe the effect of the charge separation through the voltage measurable at the terminals.
So, is it really "not there" or is it just difficult to find a path along which it would be observable?
If there is no field, then what did Mabilde measure in his setup? Because his setup modeled after the McDonald paper shows 0.25V across a quarter segment of the loop, and that is obviously way to much for just Ohms law in action.
I'm still not done thinking this through but at this point I have an inkling that when I'm done, I will have to apologize to @bsfeechannel :palm:
an electric field in the wire if it's not stationary,
Once again... Says the person with no credentials that dropped this jewel:
"A transformer winding is just a series of loops connected in series. The electric field resides in the space between each turn."
Well, but that is true.
You can read and learn, if you want.
http://web.mit.edu/6.013_book/www/chapter10/10.1.html (http://web.mit.edu/6.013_book/www/chapter10/10.1.html)
There are a lot of idealizations in the link provided: "Magnetoquasistatic Electric Fields in Systems of Perfect Conductors". I hope one day we have perfect conductors!
"Same side" seems to be "geometrically on the same side relative to the magnetic flux". That means the chosen path must never encompass any area that is inside the magnetic flux. As long as you stick to that, you're good.
I will have to apologize to @bsfeechannel :palm:
OK, so let's imagine I connect my scope to the ends of the top wire (A1 and A2 IIRC) and I repeat the experiment with the full loop in place and then with the resistors disconnected so that I only have the wire with open ends. Then I do the same routine with my magic electroscopes. What do I see?
:phew:"Same side" seems to be "geometrically on the same side relative to the magnetic flux". That means the chosen path must never encompass any area that is inside the magnetic flux. As long as you stick to that, you're good.
You got that right. It all boils down to geometry. Not electricity. Electricity works as usual.QuoteI will have to apologize to @bsfeechannel :palm:
No worries.
The selector is the presence or better the absence of magnetic flux inside the measurement loop.
The beauty of it is that [correct voltage of far branch] + [emf with correct sign] = [voltage read by multimeter]
That also explains why you cannot measure partial turn voltage, but only integer multiples.
PS: after some more headscratching, I think I understood why you cannot see any voltage across the loop wire: every path that involves the piece of wire between the resistors and that does not go around the center of the electric field will sum up to 0. Therefore, if you just naively connect you voltmeter probes to the points "A1" and "A2", that path will only observe the voltage across the wire according to Mr. Ohm. No need to argue with electric charge being counteracted by another electric field.
And Lewin's supporters went the obfuscation way again! Paragraphs and paragraphs of gibberish.
And Lewin's supporters went the obfuscation way again! Paragraphs and paragraphs of gibberish.
People who studied it, prefer to call it physics.
But I am sure it is gibberish, to you.
Alright, IIRC R1 = left, R2 = right, A1 is top of R1.......D2 is bottom of R2. So if we are measuring R2 with a voltmeter on the right, we are also measuring the equal voltage comprised of the contribution of the loop and R1. Assuming clockwise current flow, the voltage calculated across R2 is I*R2 and the other matching voltage would be the EMF (A2-A1) - (I*R1) - EMF (D1-D2). Or, if I've botched the signs, something like that. Is that right?
So how does this work when you have only a partial turn or a wire that goes straight through a core like a current transformer?
My understanding of the difficulty of measuring partial turns was a bit different, I think, but perhaps the two can be reconciled--or I'm wrong. So how does this work when you have only a partial turn or a wire that goes straight through a core like a current transformer?
I have no idea what the points A2, A1, D2, D1 refer to - probably they are present in the original Lewin drawing but I do not have it at had now. But I am a bit troubled by your use of "EMF (A2-A1)" and I believe therein lies the rub. You are still trying to apply Kirchhoff and you are implicitly assuming the wires are like 'batteries'. No, you need to let go of that because there is no longer the Eind field in the wires. It has been obliterated by the Ecoul field. This is what KVLers have trouble accepting.
A partial turn of wire is not a closed circuit, so it cannot have a current flowing.
But this falls out of the boundaries of magneto-quasistatics.
Your follow-up question - because I've developed this ability to read minds - is "what about partial inductances?
Here is the best demonstration I have found that Lewin is wrong and Electroboon/Mehdi is right. The video is by 'fromjesse'
The problem with this demonstration is that KVL only "holds" in a very particular placement of the probes. If you try to measure from the outside of the ring the voltages will be different. Confirming what Lewin said: you can measure two different voltages at the same time when you have a varying magnetic field.
Here is the best demonstration I have found that Lewin is wrong and Electroboon/Mehdi is right. The video is by 'fromjesse'
This is no different from Mabilde's probing.
Now, don't be alarmed if what follows will sound gibberish (and probably pompous and faggotish) to you.
What the Mabilde probing does is to run the probes at right angle with the induced electric field inside the loop. This will eliminate the contribute of the Eind field along the probes, leaving it untouched in the arc that is probed. BUT they are not considering the contribute of the coloumbian electric field Ecoul that is present in the arc AND in the probes. And it is not perpendicular to them, so they are not cancelling the effects on the probes themselves.
In the end, what they measure in absence of resistors is not the actual voltage along (note that I use alond, because path matters) the probed arc, but only the contribute of the coloumbian field along the probes (because in the arc Ecoul = Eind but they are opposite and they cancel so there is no contribute there). And being Ecoul conservative, this value is equal to Ecoul in the arc.
They are measuring a PARTIAL contribute to the actual voltage, namely the part that is ascribed to the coloumbian field Ecoul alone.
I'm not a 'KVLer'
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1320449;image)
QuoteA partial turn of wire is not a closed circuit, so it cannot have a current flowing.Why is it relevant whether or not current is flowing?
QuoteYour follow-up question - because I've developed this ability to read minds - is "what about partial inductances?Your Kreskin abilities may be failing you, as I was not thinking that.
And this is what a KVLer would do. Why do you compute partial contribute to the emf at all? And only on the horizontal branches? Write the equations by listing the voltage drops on one side, and the linked emf on the other (zero if absent)
What is the definition of inductance?
And this is what a KVLer would do. Why do you compute partial contribute to the emf at all? And only on the horizontal branches? Write the equations by listing the voltage drops on one side, and the linked emf on the other (zero if absent)
It was not my idea to draw the diagram this way, it is how Lewin drew it, AFAIK the 'horizontal branches' aren't really intended to represent the actual physical layout. As for the way I've written the EMF part, I was simply trying to interpret what you wrote to make sure I understood it correctly. Are you saying that geometrical accuracy issues aside, you simply cannot break down the EMF into two parts?
But, anyway... What do you think would change in the Lewin ring if, instead of a perfect conductor, you had a highly conductive copper conductor?
I tell you what: almost nothing. And certainly nothing of relevance. The only difference is that, instead of zero electric field and zero voltage drop in the conductors, you will see an almost negligible electric field E = j /sigma_copper and an almost negligible voltage drop of a handful of microvolts. Against the hundreds of millivolts of drops at the resistors.
It was not my idea to draw the diagram this way, it is how Lewin drew it, AFAIK the 'horizontal branches' aren't really intended to represent the actual physical layout.
As for the way I've written the EMF part, I was simply trying to interpret what you wrote to make sure I understood it correctly. Are you saying that geometrical accuracy issues aside, you simply cannot break down the EMF into two parts?
QuoteWhat is the definition of inductance?Hmmm... L = V/(dI/dt) or something like that?
So where are you going with that? Are you going to claim that unless current is flowing, you can't have a definite voltage?
There's also the EMF in the resistors that you need to account for, since they're part of the loop. At this point it doesn't really make sense to break EMF down into parts any more, at least not for the sake of the computation: the total EMF around the loop is given as 1V.
But, anyway... What do you think would change in the Lewin ring if, instead of a perfect conductor, you had a highly conductive copper conductor?
I tell you what: almost nothing. And certainly nothing of relevance. The only difference is that, instead of zero electric field and zero voltage drop in the conductors, you will see an almost negligible electric field E = j /sigma_copper and an almost negligible voltage drop of a handful of microvolts. Against the hundreds of millivolts of drops at the resistors.
Really, almost nothing? The attached image is from 'fromjess' experiment which shows a significant voltage drop between two points in the ring. Hard to see, but in the attached image I think it is 184mV. You can clearly see from the video that you can measure a sizeable voltage between any two arbitrary points around the copper ring. As he says it in the video "so we can measure positive and negative voltages all around this dial". How do explain that now?
Picture yourself in a boat on a river.
KVL holds for any placement of the probes, if you account for the probes as being part of the circuit.
Check this video by 'RDS Academy' which explains it in more depth. The conclusion is clear: Lewin messed up the measurement:
But, anyway... What do you think would change in the Lewin ring if, instead of a perfect conductor, you had a highly conductive copper conductor?
I tell you what: almost nothing. And certainly nothing of relevance. The only difference is that, instead of zero electric field and zero voltage drop in the conductors, you will see an almost negligible electric field E = j /sigma_copper and an almost negligible voltage drop of a handful of microvolts. Against the hundreds of millivolts of drops at the resistors.
Really, almost nothing? The attached image is from 'fromjess' experiment which shows a significant voltage drop between two points in the ring. Hard to see, but in the attached image I think it is 184mV. You can clearly see from the video that you can measure a sizeable voltage between any two arbitrary points around the copper ring. As he says it in the video "so we can measure positive and negative voltages all around this dial". How do explain that now?
That measurement has nothing to do with the fact that the ring is made of a finite conductivity conductor. You would have basically the same measure even if they were superconducting traces.
And I have already explained why he gets those reading in my answer to you above.
It is not my fault if you cannot make sense of it.
Both fromjesse and RSD Academy resort to deleting comments that tell them they are wrong, which goes to show how insecure they are about what they dish out to their viewers.
KVL holds for any placement of the probes, if you account for the probes as being part of the circuit.
No. It doesn't. He even shows a video from our fellow EEVBlogger Joeqsmith where he clearly demonstrates that the positioning of probes affects the measurement.
This is what we call cognitive dissonance: KVL holds for any placement of the probes, as long as you place them in a very specific and unique position.
Give me a break.QuoteCheck this video by 'RDS Academy' which explains it in more depth. The conclusion is clear: Lewin messed up the measurement:
He concludes that Lewin doesn't know Ohms law. I wonder how could he have fooled MIT, which I thought was one of the most, if not the most, prestigious technology institutes in the world, for 43 years, as he doesn't know Ohms law, doesn't know how to model a circuit, doesn't know how Kirchhoff law works, doesn't know how to probe a circuit.
How could they have given him these awards:
1978 – NASA Award for Exceptional Scientific Achievement
1984 – Alexander von Humboldt Award
1984 – Guggenheim Fellowship
1984 – MIT Science Council Prize for Excellence in Undergraduate Teaching
1988 – MIT Department of Physics W. Buechner Teaching Prize
1991 – Alexander von Humboldt Award (again)
1997 – NASA Group Achievement Award for the Discovery of the Bursting Pulsar
2003 – MIT Everett Moore Baker Memorial Award for Excellence in Undergraduate Teaching
2011 – first recipient of the Educator Award for OpenCourseWare Excellence (ACE)
Lewin must be a master con man, no doubt. Or the MIT is a joint. Or both.
The RDS Academy dude also accuses Lewin of defying the scientific and engineering establishment and textbooks. I've never seen a reputable textbook both of engineering and physics which claims KVL holds under a varying magnetic field. In fact I've seen exactly the opposite. They call our attention to the fact that this cannot happen.
You forgot this 'achievement': Victim In Walter Lewin Online Course Sexual Harassment Case Comes Forward
https://www.huffpost.com/entry/walter-lewin-sexual-harassment-mit_n_6532698 (https://www.huffpost.com/entry/walter-lewin-sexual-harassment-mit_n_6532698)
Really, almost nothing? The attached image is from 'fromjess' experiment which shows a significant voltage drop between two points in the ring. Hard to see, but in the attached image I think it is 184mV. You can clearly see from the video that you can measure a sizeable voltage between any two arbitrary points around the copper ring. As he says it in the video "so we can measure positive and negative voltages all around this dial". How do explain that now?
I had already envisioned a more apt analogy, a circular canal with a circulating stream of water.
The main questions seem to be where and how those forces are applied and then how and why the system would react to changes in the path, such as taking the test leads out of the plane.
Really, almost nothing? The attached image is from 'fromjess' experiment which shows a significant voltage drop between two points in the ring. Hard to see, but in the attached image I think it is 184mV. You can clearly see from the video that you can measure a sizeable voltage between any two arbitrary points around the copper ring. As he says it in the video "so we can measure positive and negative voltages all around this dial". How do explain that now?
What is funny is that for some magic reason the copper rings generate voltages, while the resistors drop them. As if the copper rings were not resistors themselves.
I wonder what would happen if if the resistors took up all the circumference of the rings, leaving no space for the probes to move.
So much for he Lewin clock. Entertaining. But hardly scientific.
To go back to the inductance of a partial turn, in order to talk about the flux linked you need to define a surface. So, what is the surface enclosed by a partial turn? It's a very delicate concept and it is better to leave it alone or we would need a new thread only for that.
What is funny is that for some magic reason the copper rings generate voltages, while the resistors drop them. As if the copper rings were not resistors themselves.
I wonder what would happen if if the resistors took up all the circumference of the rings, leaving no space for the probes to move.
To go back to the inductance of a partial turn, in order to talk about the flux linked you need to define a surface. So, what is the surface enclosed by a partial turn? It's a very delicate concept and it is better to leave it alone or we would need a new thread only for that.
OK, so then lets not talk about flux and surface. Consider a straight conductor going through a toroid core, as you would see in a current transformer. An increasing current in the coil of the current transformer should result in voltage at the ends of the rods, no?
I was being sarcastic. Anyway, thanks.
Total electric field in the rod is zero, and you will observe a voltage, but to measure it correctly - apart from an insanely high impedance voltmeter - you have to place the voltmeter in the 'hole' of the torus, so as not to link any of the flux in the core.
But, please, produce a drawing.
(Why this 'degenerate' example? Have you already solved all doubts about the circular ring?)
We can compute the contribution of partial inductance as path integrals of the vector potential. I am not sure it's possible to measure partial contributions.
A resistor under the influence of the external varying magnetic field also behaves as non-ideal voltage source.
Interesting problem, but unnecessary to understand the Faraday-Kirchhoff dispute.
So, what is wrong with measuring voltages correctly? The experiment is there: the voltages add to zero. KVL holds if you know how to measure voltages in a varying magnetic field. Lewin didn't measure in his experiment correctly and he got the wrong conclusions from his results. RSD Academy summarizes it nicely:
"Dr. Lewin is disagreeing with the vast majority of the scientific establishment, he's disagreeing with the vast majority of textbooks, he's disagreeing with the vast majority of professors of both electrical engineering and physics and his postulation that Kirchhoff's voltage law doesn't hold is based on a incorrect application of ohm's law not knowing how ohm's law has to be applied to a voltage source. Then he performs an experiment to prove his premise but he doesn't take precautions to make sure that the magnetic fields don't affect his measurements."
In short, the wire is never consider alone. It is implicitly considered part of a complete loop.
A resistor under the influence of the external varying magnetic field also behaves as non-ideal voltage source.
But, but, but, but fromjesse said that the copper rings generate voltages, while the resistors drop it! How can I properly learn Ohms law, KVL, good probing and oscilloscope operation if you guys keep contradicting each other? Aw, unbelievable!
In short, the wire is never consider alone. It is implicitly considered part of a complete loop.That may make your theory and math work out more clearly to you, but I think it is a mistake. It's true that, for example, a wire going straight through a current transformer is considered to be 1 turn because there is typically a return wire somewhere, but that's not why it actually works. The interaction between a varying magnetic field and the charges in a wire is a local (microscopically so) effect
but if you try to measure the voltage with a voltmeter you will necessarily end up linking integer multiples of the EMF.
Interesting problem, but unnecessary to understand the Faraday-Kirchhoff dispute.I guess this is an important issue since KVLers out there are claiming that the wires in the loop are standalone inductors that generate voltage to the circuit. This may come from the fact that you can actually calculate the inductance of a straight stretch of wire.
In short, the wire is never consider alone. It is implicitly considered part of a complete loop.
That may make your theory and math work out more clearly to you, but I think it is a mistake. It's true that, for example, a wire going straight through a current transformer is considered to be 1 turn because there is typically a return wire somewhere, but that's not why it actually works. The interaction between a varying magnetic field and the charges in a wire is a local (microscopically so) effect and Faraday's Law is a mathematically proven observation that says that for a given area and a varying total flux through the area, the EMF around the perimeter area adds up to a number, and that number only depends on the rate of change of the total flux.
but if you try to measure the voltage with a voltmeter you will necessarily end up linking integer multiples of the EMF.
OK, last question before I actually present something on the locality issue.
Do you need to use a voltmeter (with test leads) to measure voltage?
>:D
For your example with the wire segment in the middle of the toroid coil, consider the plane going through the wire. The electric field goes in a circular direction around the magnetic cores, so two sets of ellipse shapes. If the wire is at the center, the electric field there would be straight along the wire.
The wire is a good conductor, so it has net zero electric field inside the wire. At the surface the tangential field must be zero. So the charge in the wire must arrange itself to counteract the electric field. This results in the charges moving to the ends of the wire. One end will be positively charged, the other negative.
So now you know what the fields are and what the charge distribution is. Problem solved.
What about voltage? The voltage depends on path.
So, for example, it doesn't matter where in the toroid of the current transformer the wire is, it still reads the same because...math. And in the Lewin device, it doesn't matter if the solenoid is off center, the total EMF on the ring adds up to the same amount. That doesn't mean that the EMF is always evenly distributed nor that we can always consider it only as a total around the perimeter.
So there's the crux of the problem. My straight wire, or any partial loop for that matter, ends up with charged ends, which outside of the particular conditions at hand would be considered to be a voltage and could be measured with traditional test instruments. So what is a voltage?
In short, the wire is never consider alone. It is implicitly considered part of a complete loop.
Please modify your post to include the "traditional test instrument" and the measuring procedure adopted.
What I mean is that if you had the same wire ends but absent any external fields and achieved the exact same concentration of charge at the ends by some other means (like a battery in the middle of the wire), and measuring the voltage with a plain voltmeter. Before you protest about the battery, I'm not interested in the means, just the concentration (distribution) of charge--which should be definite, even if we have difficulty measuring it.
" if you had the same wire ends but absent any external fields and achieved the exact same concentration of charge at the ends by some other means"So, you want to take away half of the physical excitation that make your system what it is. Sure, if you pin the charges with nails and turn off the current in the transformer so as to kill the flux, you will see an electric field in the space where the rod was, and you will measure a voltage that will be different from zero. But the configuration of the electric field will be different from that around the rod when the transformer is powered.
Humor me, guys. See the attached picture. All wires are actual wires and interact with fields, but have negligible resistance. R1 can be any value, I don't think it matters. Assume EMF=1V. Predict the voltages shown on V1 and V2, using KVL and Faradays Law.
I know the question is not directed at me, but would some sort of thermoelectric emf do? Because I showed that very example to the same blockheads before and nothing happened.
1) You did not name the instrument, nor did you show the measurement procedure. Did you realize that?
And I know where you are going (much in the same way that yesterday I knew we would have ended up discussing partial inductances :-) ). You want to define voltage as the scalar potential difference.
You are free to do that, and some do, but you must be aware that with that definition of voltage you can't do anything useful without supplying the magnetic vector potential A. The reason, as I said before, is that it the scalar electric potential is insufficient to completely characterize the system. You cannot even apply Ohm's law.
Suppose I place a loop made with one resistor, the voltmeter, and its probes, near the magnetic flux region. Would you spend even a microsecond of your time to check that the induced field is being compensated? Or would you rather go: "nah, there is no flux in my measurement loop, I can apply KVL, no problem!"
Suppose I place a loop made with one resistor, the voltmeter, and its probes, near the magnetic flux region. Would you spend even a microsecond of your time to check that the induced field is being compensated? Or would you rather go: "nah, there is no flux in my measurement loop, I can apply KVL, no problem!"
Do you mean a loop like the one in the attached picture? If so, and if you measure correctly, KVL works perfectly, once again!
It has been asserted here that you can't have a voltage on a conductor that is a partial turn or a partial ring.
I'll tell you what my crystal ball forecasts: that your method to measure voltage across the rod will force you to move the sensing instrument on a path that, together with the rod, will form a closed path around the variable magnetic region.
Suppose I place a loop made with one resistor, the voltmeter, and its probes, near the magnetic flux region. Would you spend even a microsecond of your time to check that the induced field is being compensated? Or would you rather go: "nah, there is no flux in my measurement loop, I can apply KVL, no problem!"
Do you mean a loop like the one in the attached picture? If so, and if you measure correctly, KVL works perfectly, once again!
You are the one calling others 'blockheads'.
Seems to me you have yet to finish coloring your EM book.
We are talking infinitely long solenoids and toroids to confine the magnetic flux in the core. And you come up with a pancake?
Don't you even realize what is wrong with your setup?
No, your insistence on a closed path is your downfall. You only insist on it because it makes your math work.
Forget nonconservative fields. Put your rod in a conservative field, an electrostatic field. It will 'charge up' by induction. You will have opposite charge at the extremes. Now measure your absolute voltage with your method. It should be zero.
Is it zero?
KVLers seem to think Lewin has come up with some extravagant theory, but this is not his theory: it's plain and simple classical electrodynamics. When Lewin said 'all textbook are wrong' he meant introductory books talking about how to solve LR circuit. The 5 + 3 - 8 = 0 vs 5 + 3 = 8 way to apply KVL or Faraday in lumped dynamic circuits. There are tons of EM books that agree with Lewin on this matter. Purcell is one of them. He treats the ring explicitly. Haus and Melcher is another one. Faria is another. I can go on an on... There are video from professors of MIT, Purdue University, Cornell University that apply Faraday the way Lewin does, and that say that voltage is no longer unique in a nonconservative settings.
(And who do you have? A comedian and three guys in a garage?)
Please, open an EM book. One that is not about coloring pictures.
And yes, I did the experiment myself. My transformer is in the guest room, under a nightstand; my Lewin ring is in a box where I keep jumpers and connectors; my scope in on my desk. Why? Do you doubt the result of the measurement? Everybody agrees on those. Why wasting time showing another identical experiment?
What struck me as interesting is that of all the stuff that has been posted here, Youtube, wherever, it never becomes clear what the disagreement is about.
What is voltage? It is the potential energy electric charges have to go from one point to another.
The addition of meter probes doesn't affect what you are going to measure through the red or green paths. And what is more annoying is that when KVLers measure the voltages through the green path and the red path and encounter exactly what the theory predicts, they say that the theory is wrong.
Forget nonconservative fields. Put your rod in a conservative field, an electrostatic field. It will 'charge up' by induction. You will have opposite charge at the extremes. Now measure your absolute voltage with your method. It should be zero.Why would it be zero?
Is it zero?
There are tons of EM books that agree with Lewin on this matter. Purcell is one of them. He treats the ring explicitly. Haus and Melcher is another one. Faria is another. I can go on an on... There are video from professors of MIT, Purdue University, Cornell University that apply Faraday the way Lewin does, and that say that voltage is no longer unique in a nonconservative settings.
(And who do you have? A comedian and three guys in a garage?)
So how comes that when you eliminate the influence of the varying magnetic field on the measuring instrument KVL works perfectly? Here are the results from 'fromjesse' (from his garage I guess?):I have already explained how fromjesse and Mabilde obtain that reading. They are measuring the contribute of the Ecoul field in their probes. And that contribute is equal to the contribute of Ecoul in the arc they measure.
Please, open an EM book. One that is not about coloring pictures.
I have! As a matter of fact, I tediously transcribed a whole section of one (with equations and figures!) in a similar thread a couple of years back. You know, just to make sure everybody was talking about the same f*king thing:
https://www.eevblog.com/forum/chat/does-kirchhoffs-law-hold-disagreeing-with-a-master/msg2352807/#msg2352807 (https://www.eevblog.com/forum/chat/does-kirchhoffs-law-hold-disagreeing-with-a-master/msg2352807/#msg2352807)
The closed line integral is taken along the filament, directly between the capacitor plates and points 0 and 1, as indicated by the dashed line. The contribution from the perfectly conducting filament is zero, because tangential E must be zero there; this includes the helix, surprising as that may be.
voltage is no longer unique in a nonconservative settings.No longer unique? Sort of reminds me of the Second Vatican Council abolishing purgatory.
That's one definition. The whole point of my post is that there is another, whether you believe it to be an acceptable one or not. The nature of the disagreement, IMO, is that your KVLers seem to have instinctively adopted the definition that matches my explanation of absolute voltage. In KVL-world, your definition of voltage is what fails in a non-conservative field, not KVL.
I think the KVLers have settled on the approach of using test probes that are perpendicular to the plane (it's not a two-dimensional universe) and extending those leads far enough out that the rotational E-field is negligible. So no in-plane paths. This eliminates the 'interference' that would otherwise prevent an accurate measurement.
So how comes that when you eliminate the influence of the varying magnetic field on the measuring instrument KVL works perfectly? Here are the results from 'fromjesse' (from his garage I guess?):I have already explained how fromjesse and Mabilde obtain that reading. They are measuring the contribute of the Ecoul field in their probes. And that contribute is equal to the contribute of Ecoul in the arc they measure.
A good setup to find a partial component of the actual voltage.
There are tons of EM books that agree with Lewin on this matter. Purcell is one of them. He treats the ring explicitly. Haus and Melcher is another one. Faria is another. I can go on an on... There are video from professors of MIT, Purdue University, Cornell University that apply Faraday the way Lewin does, and that say that voltage is no longer unique in a nonconservative settings.
(And who do you have? A comedian and three guys in a garage?)
So, will your method give zero voltage between two points on the surface of a conductor, in electrostatic conditions? Can you prove it?
This does not add to the argument. It is just an observation, but it is interesting to note that the KVLers' champions are always academic and engineering underdogs. They have no paper, scientific or engineering, published by a reputable scientific or engineering publisher with a sound and consistent argument that KVL holds for varying magnetic fields. Just a bunch videos with contradictory statements, Lewin bashing and the usual request for subscriptions, likes, and membership money.
Here, read the transcript (or watch the video) of the conclusion from the video from Bob DuHamel from the YouTube channel RSD Academy. He can explain it way better than me:
Dr. Lewin is disagreeing with the vast majority of the scientific establishment he's disagreeing with the vast majority of textbooks he is disagreeing with the vast majority of professors of both electrical engineering and physics and his postulation that Kirchhoff's voltage law doesn't hold is based on a incorrect application of ohm's law not knowing how ohm's law has to be applied to a voltage source.
Then he performs an experiment to prove his premise but he doesn't take precautions to make sure that the magnetic fields don't affect his measurements. In the end he says “look at the math proves I'm right” well the math is right. He is right about the non-conservative fields and the conservative fields, and if we put a loop of wire in that non-conservative field that loop of wire gets a current and the electric fields in the wire are still non-conservative. But as soon as we either make a gap in the loop or put some resistance in there now we have a backup of energy where that gap is or where the resistors are, where, we get now a measurable voltage, a measurable difference in potential where we are now going up in potential and then back down in potential and we are no longer non-conservative. We are now conservative so we end up with a conservative circuit or conservative fields in the circuit even though they're embedded in a non-conservative field.
There are tons of EM books that agree with Lewin on this matter. Purcell is one of them. He treats the ring explicitly. Haus and Melcher is another one. Faria is another. I can go on an on... There are video from professors of MIT, Purdue University, Cornell University that apply Faraday the way Lewin does, and that say that voltage is no longer unique in a nonconservative settings.
(And who do you have? A comedian and three guys in a garage?)
This does not add to the argument. It is just an observation, but it is interesting to note that the KVLers' champions are always academic and engineering underdogs. They have no paper, scientific or engineering, published by a reputable scientific or engineering publisher with a sound and consistent argument that KVL holds for varying magnetic fields. Just a bunch videos with contradictory statements, Lewin bashing and the usual request for subscriptions, likes, and membership money.
And that a lot of... alternative truths. To say the least.
But you probably won't find many confutations in the comments section, because Duhamel, as fromjesse delete the comments that tell them they are wrong and why. For example, in his last video "Voltage in a loop is weird", a post by Silicon Soup stating that by putting the probes inside the magnetic region a voltage was induced in the loop has disappeared.
I would like to note that the universe doesn't care about our discussion.
My first impression of the matter was that it was much ado about nothing and just one of those quirks that I don't fully understand but don't need to.
But here we are. I still think it is much ado about nothing--perhaps no more than a notational convention
--but perhaps I and others will learn some stuff in the process.
Perhaps one reason Lewin chose to present this the way he did was to fire up his bored students, perhaps he likes the attention--as seems the case.
Dr. Lewin is disagreeing with the vast majority of the scientific establishment he's disagreeing with the vast majority of textbooks he is disagreeing with the vast majority of professors of both electrical engineering and physics and his postulation that Kirchhoff's voltage law doesn't hold is based on a incorrect application of ohm's law not knowing how ohm's law has to be applied to a voltage source.
And that a lot of... alternative truths. To say the least.
It's more serious than that. It's about pseudo-scientific claims.
you can hook up a meter across the resistor and measure its voltage, and across the wire and measure zero volts. The voltage is only across the resistor. No metaphysics. Only physics.
In the KVLer approach, the probes form a loop drenched in the varying magnetic field. Funny that you mentioned a three dimensional world but you failed to consider the three dimensional loop that you configured with that arrangement.
I was using YOUR definition of voltage, which really fails in a non conservative field, you're right.
Not only the theory predicts that, but also you can hook up a meter across the resistor and measure its voltage, and across the wire and measure zero volts. The voltage is only across the resistor. No metaphysics. Only physics.
In the KVLer approach, the probes form a loop drenched in the varying magnetic field. Funny that you mentioned a three dimensional world but you failed to consider the three dimensional loop that you configured with that arrangement.I believe they choose their loop so that it bisects the solenoid so that there is no net flux. Or at least that is what is attempted and claimed.
Humor me, guys. See the attached picture. All wires are actual wires and interact with fields, but have negligible resistance. R1 can be any value, I don't think it matters. Assume EMF=1V. Predict the voltages shown on V1 and V2, using KVL and Faradays Law.
V1 is zero, V2 is 1V. (didn't check the sign just saw the thumbnail), might as well be -1V
It's easy if you check if your measurement loop (voltmeter + probes + branch you want to know the voltage of) contains or does not contain the flux.
Now I have a question for you.
Suppose I place a loop made with one resistor, the voltmeter, and its probes, near the magnetic flux region. Would you spend even a microsecond of your time to check that the induced field is being compensated? Or would you rather go: "nah, there is no flux in my measurement loop, I can apply KVL, no problem!"
EDIT: Yep, the transformer trick would do. IIRC Big Clive used the whole secondary of a transformer to step down the voltage. From 240-->12V to 240 ---> 240-12V or something like that. Caveat: the current must be sustained by both windings.
In principle we could use the radial probing to extract a finely varying voltage from a solenoidal coil immersed in a magnetic field. Instead of going one turn at the time, we can have a continuous (well, only marred by asperities in contact) voltage from start to finish. Mechanical nightmare, of course.
What Mabilde and "fromjesse" did was change the experiment until they could explain it with KVL. That's like, when you get some task assigned in a test and you cannot solve it, you change the task until you can. I don't think that'll earn you any points.
What Mabilde and "fromjesse" did was change the experiment until they could explain it with KVL. That's like, when you get some task assigned in a test and you cannot solve it, you change the task until you can. I don't think that'll earn you any points.
Nope! I am pretty sure that Mabilde, fromjesse, electroboom, and many other people, including myself, saw Lewin's experiment and immediately thought "bad proving"! Why? Because all of us have been there before, many, many times. If you are not careful setting your measuring equipment you'll pick-up all kinds of unwanted stuff. You quickly learn that oscilloscopes and their proves are very good at that!
Or 'bad probing'. :-DD
But seriously, you can also hook up a meter and measure voltage on both.
Forget nonconservative fields. Put your rod in a conservative field, an electrostatic field. It will 'charge up' by induction. You will have opposite charge at the extremes. Now measure your absolute voltage with your method. It should be zero.
Is it zero?
Remember when I told you that engineers take classes in vector calculus? It is so as not to incur in errors in their reasoning when analyzing some phenomenon. Your configuration is measuring only the voltage across the resistor, exactly what you'd measure if your meter and probes were in the plane. In fact any position of the meter and probes in red in the picture below will do that. This is because the area they define together with the resistor is not traversed by the lines of the varying magnetic field. Faraday's law. KVL won't tell you that.
I believe they choose their loop so that it bisects the solenoid so that there is no net flux. Or at least that is what is attempted and claimed.
QuoteI was using YOUR definition of voltage, which really fails in a non conservative field, you're right.
Fails at what? The two definitions are irreconcilable as far as I can see in this specific instance. That's the issue.
I'd say vice versa, because the path through V2 is not in the magnetic flux and the branch voltage is zero, so I'd think V2=0 and V1=1V (or -1V, I didn't check the field orientation either). If I'm wrong, I'd really like to hear your explanation.Humor me, guys. See the attached picture. All wires are actual wires and interact with fields, but have negligible resistance. R1 can be any value, I don't think it matters. Assume EMF=1V. Predict the voltages shown on V1 and V2, using KVL and Faradays Law.V1 is zero, V2 is 1V. (didn't check the sign just saw the thumbnail), might as well be -1V
It's easy if you check if your measurement loop (voltmeter + probes + branch you want to know the voltage of) contains or does not contain the flux.
QuoteNow I have a question for you.Hm, I'd probably still picture the electric field vortex, because for me that's easier to visualize. But no I'd not spend any time actually checking, I'd know that if the field axis is outside of my loop area, the electric fields must sum up to 0. To me the electric field is somehow more "intuitive" because that's what the charge in the loop is interacting with.
Suppose I place a loop made with one resistor, the voltmeter, and its probes, near the magnetic flux region. Would you spend even a microsecond of your time to check that the induced field is being compensated? Or would you rather go: "nah, there is no flux in my measurement loop, I can apply KVL, no problem!"
I believe what many of us participating in the discussion initially didn't understand, me explicitly included, is that Dr. Lewins experiment must be seen as a whole, including his choice of probing the voltages. The whole idea about formulating a "law" in science is to be able to explain and predict the outcome of an experiment, and as I already said but probably nobody really took notice, the test instrument setup including geometrical arrangement of probe wires is inevitably part of the experiment.
For me that concludes the discussion. I've learned a lot in the course of it and I have a new understanding of electromagentism through it. I'll go back to the sidelines now for a while.
Remember when I told you that engineers take classes in vector calculus? It is so as not to incur in errors in their reasoning when analyzing some phenomenon. Your configuration is measuring only the voltage across the resistor, exactly what you'd measure if your meter and probes were in the plane. In fact any position of the meter and probes in red in the picture below will do that. This is because the area they define together with the resistor is not traversed by the lines of the varying magnetic field. Faraday's law. KVL won't tell you that.
I don't know why, at this point in the discussion, you think this is a revelation to me. I deliberately drew that diagram to illustrate that the position of the voltmeter doesn't matter, as you've drawn. I don't need Faraday's Law or KVL to tell that, all I need to know is that I'm out of the region of flux and thus there are no rotational E-fields to become tangential to my wires and push the charges around. That's the whole point of extending out the partial turn.
I don't know why, at this point in the discussion, you think this is a revelation to me. I deliberately drew that diagram to illustrate that the position of the voltmeter doesn't matter, as you've drawn
I don't need Faraday's Law or KVL to tell that, all I need to know is that I'm out of the region of flux and thus there are no rotational E-fields to become tangential to my wires and push the charges around.
Nope. YOUR definition of voltage is just a special case of the more general definition of voltage which is the line integral of the electric field along a certain path, be it the field conservative or non-conservative.
They're not irreconcilable.
Which is another thing I think I understood now: charge particles that are inert referenced to the magnetic flux are not interacting with the magnetic field, even if it's changing.
Which is another thing I think I understood now: charge particles that are inert referenced to the magnetic flux are not interacting with the magnetic field, even if it's changing.
Whoa! My spider senses are tingling all over.
Care to rethink this?
But you said that you are measuring the voltage across both the wire and the resistor with that configuration. Or did get it wrong?
By irreconcilable I mean that they aren't going to be the same number in a non-conservative field.
You say "be it conservative or non-conservative", but I think perhaps the Magneto-Quasi-Static idea has fooled you into thinking that the concepts from conservative fields can be applied to non-conservative fields as long as they hold steady for some period of time. I'm pretty sure that is untrue, but I'm struggling to demonstrate that.
I believe what many of us participating in the discussion initially didn't understand, me explicitly included, is that Dr. Lewins experiment must be seen as a whole, including his choice of probing the voltages. The whole idea about formulating a "law" in science is to be able to explain and predict the outcome of an experiment, and as I already said but probably nobody really took notice, the test instrument setup including geometrical arrangement of probe wires is inevitably part of the experiment. Dr. Lewin proposed a circuit and the challenge was to explain the measurements, and quite honestly, you cannot do that with Kirchhoff. It doesn't work.
The general definition of voltage depicts reality. YOUR definition of voltage depicts the struggle to understand it.
But you said that you are measuring the voltage across both the wire and the resistor with that configuration. Or did I get it wrong?
I'm measuring from one point to another. In this case, it a happens to be both across the resistor and across the partial turn, outside of any non-conservative field.
Yes, of course, but I'm pretty sure about that. It explains, IMHO, that Lorentz' force and the electromagnetic force are two independent effects and not just two sides of the same coin.Which is another thing I think I understood now: charge particles that are inert referenced to the magnetic flux are not interacting with the magnetic field, even if it's changing.
Whoa! My spider senses are tingling all over.
Care to rethink this?
"A toroidal vacuum chamber encircles the core of a large magnet. The magnetic field is produced by pulsed coils; the magnetic flux inside the radius of the vacuum chamber changes with time. Increasing flux generates an azimuthal electric field which accelerates electrons in the chamber.
In the absence of an air gap, there is little magnetic flux outside the core."
It's not my definition of voltage, it is a definition that was taught earlier in Lewin's course, among a zillion other places that it pops up.
You are just measuring a voltage due to a conservative field that is present in the resistor and between the terminals of the wire. Assuming the wire has no resistance, you can slide the meter all the way down to the left, just before you cross the lines of the mag field. You're measuring nothing else. You're not measuring the voltage due to the field in the wire. For that you need to place your meter anywhwere three-dimensionally speaking to the left of the field.
Care to provide a reference to it in Lewin's course, please?
I'll tell you what my crystal ball forecasts: that your method to measure voltage across the rod will force you to move the sensing instrument on a path that, together with the rod, will form a closed path around the variable magnetic region.
No, your insistence on a closed path is your downfall. You only insist on it because it makes your math work.
The insistence in the closed path is because we are talking about circuits, which by definition are closed paths.
How do you define the term 'equipotential'?
Let's assume I'm measuring between any two points with an analog voltmeter, just to make things a bit clearer. This would be a galvanometer in series with a resistor. So if I connect such a voltmeter to two points, current will not flow if they are equipotential, but will if there is a potential there. You can hide the entire apparatus from me, but as long as my meter and test leads are free from any external fields, B or E, I will get a certain result that will indicate whether those two points are equipotential or not. Free of external fields, there is no dispute over what voltage is. I don't need to have any knowledge of the source or cause of the voltage, or lack thereof. Or do you disagree with that as well?
Care to provide a reference to it in Lewin's course, please?
Maybe I can look a bit later, but which part do you doubt? C = 4 * pi * E0 * r or Q = CV?
It should measure zero, simply because it needs to.Emphasis mine.
Yes, of course, but I'm pretty sure about that. It explains, IMHO, that Lorentz' force and the electromagnetic force are two independent effects and not just two sides of the same coin. It would also serve as an explanation for why, as @bsfeechannel said, a wire in time varying magnetic flux doesn't have an "inner electric field" while when it is moving in a (constant) magnetic flux, there is an "inner electric field". In the case of the time varying magnetic flux the charge particles interact not with the magnetic field but with the electric field that results from the magnetic flux change. That's how I understood the Maxwell-Faraday equation: change in magnetic flux causes a rotational electric field.
First off, your machine requires two spheres, so you will have to account for the field lines going from one sphere to the other. Then you have the object you want to measure the charge of that will interact with those field lines, and the source of the field, and the whole planet beneath your feet.
And that thing about the field lines being perpendicular to the path of the spheres? Wishful thinking at its best. The moment the field induces charges on your rod, they will distort the field - not only inside the body to create the zero field, but also outside. And the distortion will be significant because the field lines needs to be perpendicular to the surface of the conductor.
And then your spheres will have induced charge themselves, that will disturb the field even more and change the charge distribution of the rod as you move near and away from it.
And why should the charge displaced on the rod jump on the spheres (which will have their own induced charge already?)
And what do you want to do in the nonconservative case? "extend the ends out to the point where the fields are negligible"??? What fields? Not the B field, it was never outside the core to begin with. So it must be the electric field. It can't be Ecoul, since it is generated by the charges themselves. Must be the induced field Eind, then. And you expect to see the displaced charge where there is no Eind field? If there is no more Eind field, what keeps the charges segregated at the extremes of the rod? All that charges of the same sign crammed together at one extreme? Wouldn't you think they'd repel each other?
And then you bring the alleged charge transferred on the spheres back together in the same place where you can measure it? My crystal ball was right. You are closing the path, after all (but let's not talk about this now). Even admitting you can magically duplicate (this could actually work) or take the charge of one extreme of the rod and the charge on the other extreme and then infer the voltage between them - you would see a voltage between them even in the electrostatic case. (because you have removed the external field Eext that causes the electrostatic induction of the rod). So, should we also say that there is a voltage between two points of a conductor in an electrostatic field?
Tequila is my lady, tonight.
As for the difficulties, experimental physics isn't simple!
Difficult, but I don't think theoretically impossible.
But I couldn't see an easy way to prove that.
But IMO it doesn't matter, closing the path far away from the action has negligible effect and you shouldn't rely on technicalities, infinitesmals or magic to make a practical theory work.
So let me get this straight. You can't prove none of your claims and you want to reinvent the wheel with a "practical" theory that doesn't rely on "technicalities, infinitesimals or magic" that again you can't even demonstrate in practice because "experimental physics isn't simple".
On the other hand, Faraday's law of induction, which renders KVL useless for varying magnetic fields, is not only easily provable, but also easily demonstrated by anyone with a spool of wire, a battery and a meter. That's how Faraday himself discovered the phenomenon. You don't need a fancy physics lab.
Start with the long U-shaped conductor. Is there potential across the ends or not?
As I was responding to Sredni and thinkfat it occured to me that there's another issue with the equipotentiality argument. In the static, conservative, irrotational field, there isn't an E-field inside the conductor because the charges instantly rearrange themselves to oppose it. Thus there is no net force on any charge within the conductor. In the case of a charge moving in a magnetic field, you accept that there is an non-conservative field inside the conductor acting on the charges, right? But then we get to the MQS system, and even though there is clearly a local force acting on charges inside the conductor--which is the EMF--
and those forces continually push charges through the conductor, that the conductor is nonetheless equipotential in the same way as in the static case, and for the same reason--there's no electric field in a conductor.
I believe what many of us participating in the discussion initially didn't understand, me explicitly included, is that Dr. Lewins experiment must be seen as a whole, including his choice of probing the voltages. The whole idea about formulating a "law" in science is to be able to explain and predict the outcome of an experiment, and as I already said but probably nobody really took notice, the test instrument setup including geometrical arrangement of probe wires is inevitably part of the experiment. Dr. Lewin proposed a circuit and the challenge was to explain the measurements, and quite honestly, you cannot do that with Kirchhoff. It doesn't work.
I beg to disagree. A proper experiment would had included many measurements from different geometric probing configurations. Lewin purposefully picked a configuration that he believed would eliminate the effect of the varying magnetic field in the measurement equipment while measuring the voltage between the top and the bottom of the ring. He ended up cancelling the effect of the magnetic field both in the probes and in the ring! That is equivalent to measure the voltage across the resistors directly.
Lewin then assumes that the voltage across any two points in the ring wire is zero volts, because he applies ohms law and the wire resistance is almost zero, and he goes AHA! KVL doesn't work!!! The problem here is that Lewin forgot that a piece of wire in a circuit under the influence a varying magnetic field doesn't behave as zero ohm resistor but as non-ideal voltage source. When you account for that extra little piece of information, all of a sudden KVL works perfectly, no matter the probing geometry, if you include the probes as part of your circuit.
Quote"A toroidal vacuum chamber encircles the core of a large magnet. The magnetic field is produced by pulsed coils; the magnetic flux inside the radius of the vacuum chamber changes with time. Increasing flux generates an azimuthal electric field which accelerates electrons in the chamber.
In the absence of an air gap, there is little magnetic flux outside the core."
I suggest watching that other MIT video, https://youtu.be/u6ud7JD0fV4. (https://youtu.be/u6ud7JD0fV4.) The thing is, the measurement loops C1 and C2 are not influenced by any magnetic flux. The demonstration even uses a toroid core to make sure that there is no flux outside of the core. There's nothing you'd need to cancel or compensate for. And the setup is not even very peculiar, the probe wires are just laying there on the bench with no particular care taken to fixate them anywhere. They're just "flopping around in the breeze".
But anyway, would you be able to explain what the oscilloscope shows in that video with just KVL?
I actually like that setup, because the core is a solid loop, there is no point in arguing "stray magnetic fields" and no way to contort the setup to "eliminate bad probing".
Check this video from 'fromjesse' with the very same experiment where he explains much better than me what is going on. The title of the video says it all: "The Lewin loop inside an iron core - KVL still holds":
https://www.youtube.com/watch?v=iDWv8QJrzUo (https://www.youtube.com/watch?v=iDWv8QJrzUo)
Sir, this is EEVBlog.
I can't imagine how you could possibly read a denial of Faraday's Law in anything I've written. If some of it seems too far out there, address a few simpler ideas.
Here is a non-closed path example without any as-of-yet uninvented machines, except I'm not sure they have electroscopes this good. What happens when the current is turned on?
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1321814;image)
Quote"A toroidal vacuum chamber encircles the core of a large magnet. The magnetic field is produced by pulsed coils; the magnetic flux inside the radius of the vacuum chamber changes with time. Increasing flux generates an azimuthal electric field which accelerates electrons in the chamber.
In the absence of an air gap, there is little magnetic flux outside the core."
Emphasis mine, this is what I was referring to. It's the electric field the electrons interact with.
IT DEPENDS ON THE PATH
Stop. This is wrong.
It is NOT the EMF. We always end up here: forgetting the role of the displaced charge. The EMF - or better, the induced electric field Eind, is compensated in the conductor by the coloumbian field Ecoul. If there is a gap and no current is flowing, this is always exactly true.
So, it is not Eind that is acting on the carriers. It is the combined effect of the EMF (represented by Eind) and the displaced charge (represented by Ecoul).
...
The circuit had just two resistors and nothing else. And his model predicted exactly what happened in practice. KVL failed on the board. And then failed on the bench.
...
The core is split, it's two toroids which both carry about half of the total flux each. His "Lewin loop" is around the center column where the two toroids join, same as the yellow reference loop, they both experience the total magnetic flux. However, when he measures the voltage across the "red" parts, his probe leads and the red wire form a loop around one of the two toroids, encompassing half of the magnetic flux. So what he actually measures is not the voltage across that red wire, it is the EMF in his measurement loop, which is, since it experiences about half of the total flux, half of the voltage induced in his reference loop.
PS: this would be a brilliant experiment: Use a split core with different permeability in each of the toroids, so that the flux is no longer evenly split. I wonder if the voltages would still add up ;)
a piece of wire in a circuit under the influence a varying magnetic field doesn't behave as zero ohm resistor but as non-ideal voltage source.
Where do we go from here?
It isn't "just two resistors and nothing else", it has a closed loop of wire in a varying magnetic field. It has a transformer (as has been pointed out over and over here). If the model doesn't include the transformer, it is an incomplete model.
It isn't "just two resistors and nothing else", it has a closed loop of wire in a varying magnetic field. It has a transformer (as has been pointed out over and over here). If the model doesn't include the transformer, it is an incomplete model.
What transformer? Replace the solenoid by a moving magnet, or by the radiation coming from a radio station. The voltages in your circuit will not add up to zero. This was not only proven theoretically but practically. It is the principle behind the reception of every radio.
And we're not discussing the model. We are discussing if it is possible to measure two different voltages at the same two points by the same or different but identical meters on a circuit subjected to an externally generated varying magnetic field.
It is. Period.
I'm afraid this won't make your argument stronger. You really need to take geometry and the fields into account and where the magnetic flux "flows".
The core is split, it's two toroids which both carry about half of the total flux each. His "Lewin loop" is around the center column where the two toroids join, same as the yellow reference loop, they both experience the total magnetic flux. However, when he measures the voltage across the "red" parts, his probe leads and the red wire form a loop around one of the two toroids, encompassing half of the magnetic flux. So what he actually measures is not the voltage across that red wire, it is the EMF in his measurement loop, which is, since it experiences about half of the total flux, half of the voltage induced in his reference loop.
PS: this would be a brilliant experiment: Use a split core with different permeability in each of the toroids, so that the flux is no longer evenly split. I wonder if the voltages would still add up ;)
One can make a lumped model by representing this charge separation by a battery in series with the wire. Now with a lumped model, KVL works fine.
But people are modeling this as lots of little batteries alternating with lots of little resistors. So the voltage through the loop goes up through the batteries and down through the resistors all around the loop. So the voltage between any two points on the loop is zero.
At the least this model is utterly confusing. The voltage between two points is zero? But what happened to ohm's law? V=IR? What about the power? The resistor is going to get hot, like an induction heater isn't it? I thought P=(I squared)R, or (V squared)/R. But there's zero voltage. So where's the power coming from? (I know, the batteries). Not a very good model.
One can make a lumped model by representing this charge separation by a battery in series with the wire. Now with a lumped model, KVL works fine.
In my mind where this modeling method breaks down badly is in the case of the uniform resistive loop. Here the loop is just a high resistance wire, for example.
If the loop is uniform, then there is no static charge anywhere in the loop. So where to put the battery?
You could just stick one battery at one spot in the loop. To me, this is a half decent approximation. It works everywhere except the section of the loop including the battery.
But people are modeling this as lots of little batteries alternating with lots of little resistors. So the voltage through the loop goes up through the batteries and down through the resistors all around the loop. So the voltage between any two points on the loop is zero.
At the least this model is utterly confusing. The voltage between two points is zero? But what happened to ohm's law? V=IR? What about the power? The resistor is going to get hot, like an induction heater isn't it? I thought P=(I squared)R, or (V squared)/R. But there's zero voltage. So where's the power coming from? (I know, the batteries). Not a very good model.
What is being induced in the coupled circuit is a current, not a voltage.
What transformer? The transformer that is there. What is a transformer? Two coils with a coupled field. It is a circuit element. If you neglect a circuit element in a circuit diagram, it is incorrect. It is no more of an error than if there was a AC (or DC) source in the loop and you neglect to put it in the circuit diagram. It is obvious that this tread isn't going to convince anyone of anything.
What is being induced in the coupled circuit is a current, not a voltage.
Really? You have a rotational E-field that exerts a force on the charge. There's no guarantee that they'll move and if there is another counterforce, they won't. A current source implies that they move no matter what.
At the least this model is utterly confusing. The voltage between two points is zero? But what happened to ohm's law? V=IR? What about the power? The resistor is going to get hot, like an induction heater isn't it? I thought P=(I squared)R, or (V squared)/R. But there's zero voltage. So where's the power coming from? (I know, the batteries). Not a very good model.
You may be right, I was just replying off the top of my head, but a current source model doesn't imply current. If I draw a current course with nothing attached to it, it is assumed that no current flows. If you get into a debate over that, it will be simillar to this thread.
What transformer? The transformer that is there. What is a transformer? Two coils with a coupled field. It is a circuit element. If you neglect a circuit element in a circuit diagram, it is incorrect. It is no more of an error than if there was a AC (or DC) source in the loop and you neglect to put it in the circuit diagram.
It is obvious that this tread isn't going to convince anyone of anything.
Why here, of course!
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1322228;image)
You tap into the Lewin ring and since the rotational E-field from the flux doesn't magically end at the ring, you need to run a wire out some distance perpendicularly to any E-field, so that there is no Eind. Once you are far enough that all fields are negligibly low, you then connect an electroscope. You can then connect the electroscopes to points A, B, C and D and see what results you get. What do you expect to see?
Are you trying to measure the contribution of the displacement charges to the field inside the wire?
The core is split, it's two toroids which both carry about half of the total flux each. His "Lewin loop" is around the center column where the two toroids join, same as the yellow reference loop, they both experience the total magnetic flux. However, when he measures the voltage across the "red" parts, his probe leads and the red wire form a loop around one of the two toroids, encompassing half of the magnetic flux. So what he actually measures is not the voltage across that red wire, it is the EMF in his measurement loop, which is, since it experiences about half of the total flux, half of the voltage induced in his reference loop.Exactly. What he had was NOT Lewin's setup. The meters that were measuring the voltages across the wires were forming additional loops around half of the magnetic field in the opposite direction. No wonder he got negative voltages.
Quote"A toroidal vacuum chamber encircles the core of a large magnet. The magnetic field is produced by pulsed coils; the magnetic flux inside the radius of the vacuum chamber changes with time. Increasing flux generates an azimuthal electric field which accelerates electrons in the chamber.
In the absence of an air gap, there is little magnetic flux outside the core."
Emphasis mine, this is what I was referring to. It's the electric field the electrons interact with.
But it's not independent from the changing magnetic field. The way I see it is they are two manifestations of the same phenomenon. (Like in the propagation of an EM wave, it's not that the changing B field causes a changing E field that causes... ). But anyway, we can consider this just nitpicking.
It appears to me that you now understand Faraday's law in full.
I cannot help imagining Lewin stroking his hands with satisfaction while, in a black hood and cloak, reads your exchange with jesuscf and mutters "Well done, my apprentice... Hihihihi.... Now, strike him down with your path integral!"
May the nonconservative force be with you.
The core is split, it's two toroids which both carry about half of the total flux each. His "Lewin loop" is around the center column where the two toroids join, same as the yellow reference loop, they both experience the total magnetic flux. However, when he measures the voltage across the "red" parts, his probe leads and the red wire form a loop around one of the two toroids, encompassing half of the magnetic flux. So what he actually measures is not the voltage across that red wire, it is the EMF in his measurement loop, which is, since it experiences about half of the total flux, half of the voltage induced in his reference loop.Exactly. What he had was NOT Lewin's setup. The meters that were measuring the voltages across the wires were forming additional loops around half of the magnetic field in the opposite direction. No wonder he got negative voltages.
bsfeechannel, in how many loops is the voltmeter circuit in the 'fromjesse' experiment as shown in the figure below? (Tip: the answer is in a previous post)
Sigh. That is not my ultimate intent nor am I sure that this will do exactly that--although perhaps it boils down to the same thing. This is not the last step. So, do I see varying electroscope readings at A,B,C and D or are they all zero?
IT DEPENDS ON THE PATHOf course it does.
To put this in context, I was comparing three phenomena- a conductor in a static, irrotational conservative field, a conductor in a rotational non-conservative field derived from dB/dt and a conductor moving across magnetic lines as in a generator, where the charges experience the Lorentz force. So in the first case, I think we all agree with your assertion. Apparently, and don't attribute this assertion to me, the third case does result in a potential gradient over the length of the conductor. Is that right or wrong? And if it is right, then how do you differentiate the effect of the Lorentz force from the local Eind force in the second example?
"and this is again (EDIT: in general) wrong for the reason above."
"But, if you consider a region of space that contains all of your piece of conductor and none of the magnetic flux, like a cylinder around the rod in the middle of the torus, in that region of space all paths you can imagine will never enclose the magnetic flux region. in this sense you can consider it as equipotential."
Can I blame the tequila?
What I am perplexed about is your fixation with 'where there are no fields'. If the charges are there, there is at least their field, so you can't do away with it. If there are no fields to push and keep them there, then the charges are no reason to accumulate there.
I am not going to touch the motional case even with a ten foot pole. We are already wasting too much space and time to address the Lewin ring and we would fall down a relativistic rabbit hole with no end. I suggest you look up Purcell for an introduction to that kind of stuff.
In reality, for a ring big enough the resistance of the ring would make the current so small that you won't be able to see anything at all, even at the terminals (imagine a ring one light yeat in radius from Lewin's solenoid).
I don't think it is a waste of space or time if it advances anyone's understanding (mine, for example) as opposed to degenerating into a food fight.
I'm only thinking of a few meters of wire and while there still will be a circular field that only diminishes with the radius
Your forgetting that the core is a toroid.
Your forgetting that the core is a toroid.
You're right. I keep bringing up the infinite solenoid to exploit the symmetry and the simple analytical expression of the field. I think we should all stick with that to make things simpler and consider the toroid as a "poor man's folded infinite solenoid" for lab experiments with voltages and currents in the ring.
It isn't "just two resistors and nothing else", it has a closed loop of wire in a varying magnetic field. It has a transformer (as has been pointed out over and over here). If the model doesn't include the transformer, it is an incomplete model.
What transformer? Replace the solenoid by a moving magnet, or by the radiation coming from a radio station. The voltages in your circuit will not add up to zero. This was not only proven theoretically but practically. It is the principle behind the reception of every radio.
And we're not discussing the model. We are discussing if it is possible to measure two different voltages at the same two points by the same or different but identical meters on a circuit subjected to an externally generated varying magnetic field.
It is. Period.
What transformer? The transformer that is there. What is a transformer? Two coils with a coupled field. It is a circuit element. If you neglect a circuit element in a circuit diagram, it is incorrect. It is no more of an error than if there was a AC (or DC) source in the loop and you neglect to put it in the circuit diagram. It is obvious that this tread isn't going to convince anyone of anything.
The difficulty with the toroid is that the folded nature makes some hands-on experimental observations difficult.
I am, however, sorely tempted to use a carbide or diamond bit to drill a small hole in the side of a formerly toroidal core to facilitate such measurements :-DD :-DD :-DD
...
But you probably won't find many confutations in the comments section, because Duhamel, like fromjesse, delete the comments that tell them they are wrong and why. For example, in his last video "Voltage in a loop is weird", a post by Silicon Soup stating that by putting the probes inside the magnetic region a voltage was induced in the loop has disappeared.
Here's the reason:
https://i.postimg.cc/vZ6BM4Wn/screenshot-3.png
...
The difficulty with the toroid is that the folded nature makes some hands-on experimental observations difficult.
How so? I have seen this experiment done on toroidal transformers (MIT), and even on EI transformers (Sam Ben-Yaakov, Ben Gurion University). The EI are 'doubly folded': you just need to be careful not to enclose the 'legs' where the flux in your measurement loop.QuoteI am, however, sorely tempted to use a carbide or diamond bit to drill a small hole in the side of a formerly toroidal core to facilitate such measurements :-DD :-DD :-DD
Why on earth would you want to do that? You need to avoid the magnetic flux region.
Please explain.
...
PS: this would be a brilliant experiment: Use a split core with different permeability in each of the toroids, so that the flux is no longer evenly split. I wonder if the voltages would still add up ;)
...Just to set the record straight, your statement is false.
But you probably won't find many confutations in the comments section, because Duhamel, like fromjesse, delete the comments that tell them they are wrong and why. For example, in his last video "Voltage in a loop is weird", a post by Silicon Soup stating that by putting the probes inside the magnetic region a voltage was induced in the loop has disappeared.
Here's the reason:
https://i.postimg.cc/vZ6BM4Wn/screenshot-3.png
...
Neither I nor Duhamel delete comments just because they disagree with us.
I don't know whether Bob deleted any specific comments,
but I don't recall deleting any specific comments, but what I did do is ban ONE particular person (felinus retardus) who was being insulting to my viewers as well as myself. I did not delete all of his comments,But you did not publish some?
Let's try to figure out the issue.
Dr. McDonald said "Lewin's circuit is within the range of applicability of Kirchhoff's loop equations, which can be used to predict measurements by the 'voltmeters' in the experiment. "
"In this sense, KVL holds, as argued by Mehdi Sadaghdar ..."
Therefore, when stores will sell AC voltmeters that can read that scalar potential difference, that definition of his will come very handy. Till then, a lot of people prefer to use actual voltage, the one that can be measured by voltmeters and that is path-dependent. It is also much easier to treat.
creating a circuit that cannot be model with a lumped component.
It's all over the circuit, and it is not a voltage. So voltmeters won't measure it.
He calculates and confirm that the two voltmeters in Lewin's experiment will show two different voltages even though connected to the same points in the circuit...
And here we come to the Mehdi problem.
in fact the vast majority of times that a voltmeter is used, the user is indeed attempting to measure that 'scalar potential' and would regard any electric fields along the path that are attributable to any other cause to be 'interference'.
And there are a lot of ways of dealing with interference. I would say that most of the KVLer/YouTubers attempts are exactly that--an attempt to find a path where that circular electric field has zero net contribution.
Quotecreating a circuit that cannot be model with a lumped component.Second, you can lump it just fine
That is why the voltmeters outside the ring measure correctly the voltages along (and across for any path that does not run around the core) the branch with the nearest resistor.
The other measurement loop is marred with an 'interfering voltage' of the EMF of one full turn.
It will give you the correct current and the correct voltages across the resistors but does not correctly describe the voltage along the arcs.
That is why the voltmeters outside the ring measure correctly the voltages along (and across for any path that does not run around the core) the branch with the nearest resistor.No, the voltmeter measures the EMF of the outside loop--the far side of the ring plus its own test leads, less the voltage drop across the far resistor.
The other measurement loop is marred with an 'interfering voltage' of the EMF of one full turn.
This is where the second Lewin 'explanation' diagram was confusing, because it showed three loops and three EMF circles in each one.
His whole demonstration is designed to provoke rather than explain
I haven't watched, but I suppose he didn't clear anything up?
But I think that in the case of his diatribe with Lewin, he really jumped the shark.
Ok, let's set the record straight. This will be my last post on the topic of your disappearing comments and Bob's merry deletions, but I really need to set the record actually straight.
...Just to set the record straight, your statement is false.
But you probably won't find many confutations in the comments section, because Duhamel, like fromjesse, delete the comments that tell them they are wrong and why. For example, in his last video "Voltage in a loop is weird", a post by Silicon Soup stating that by putting the probes inside the magnetic region a voltage was induced in the loop has disappeared.
Here's the reason:
https://i.postimg.cc/vZ6BM4Wn/screenshot-3.png
...
Neither I nor Duhamel delete comments just because they disagree with us.
I don't know whether Bob deleted any specific comments,
You literally contradicted yourself from one sentence to the other.
Sentence two says "Duhamel does not delete comments because..."
Sentence three says "I do not know whether Bob deleted any specific comments..."
Did you talk to Bob expressely about this? Sentence three says you didn't. Also says you seem fine about talking of what you do not know.
Record straightened: I can recall at least three posts that disappeared from RSD A. videos. One is the comment from Silicon Soup, stating that by running the probes in the magnetic flux region he was intercepting flux and this inducing a voltage. It was deleted along with a timestamped comment by Copernico Felinis (or, by using your non-insulting name: felinus retardus). Another one is a comment of I believe Mick Vall (Or Mark Fruchtman, a name like that... M---- --a---) where he told Bob that he was wrong and he should not be teaching this wrong concepts because it would cause confusion in students (and he also explained why and where he was wrong). The whole thread disappeared, along with other comments discussing technicalities.
So, keep your "false" to you.
And then there is that exchange with Mr. Anderson. It tells all you need to know.I don't know what you're talking about.
I don't remember not publishing any. Most of my videos have un-moderated comments, but sometimes youtube flags them and I have to go in and approve them.Quotebut I don't recall deleting any specific comments, but what I did do is ban ONE particular person (felinus retardus) who was being insulting to my viewers as well as myself. I did not delete all of his comments,But you did not publish some?
I guess that, regarding the insults, you meant comments like this one - in that case I can understand
(https://i.postimg.cc/N081Kppk/screenshot-fromjesse-insults.png)
Source: your channel - image here https://i.postimg.cc/N081Kppk/screenshot-fromjesse-insults.png (https://i.postimg.cc/N081Kppk/screenshot-fromjesse-insults.png)
Oh, my bad. That was Samuel Snerden cold open post and he was talking about Lewin. Did you ban him as well, for insulting your viewers? But of course not. Lewin is certainly not a viewer of yours.
Also about insults, and then I'll drop it definitively: I have been through the exchange you are having with ThinkFat. In just two or three comments you manage to call bsfeechannell: "clueless", "totally idiotic", "either he's fulla BS or he's not being honest", "your hero the ignorant bsfeechannel", "he's either ignorant or disingeneous".
Apart from that thing about pots and kettles, I don't think your ban was motivated by insults. You seem pretty comfortable with insults in your channel. I believe it's something else. I wonder what that could be. :-//
Maybe when you are cornered, you get insecure?Nope, look at all the other guys who were much more meticulous and thorough - they would be the ones that cornered me and caused insecurity. But you can see that the discussions go on for a LONG time, and they are still there, and those users are not banned.
QuoteLet's try to figure out the issue.
Will you start insulting people in here, as well?
If not, I can try to explain what is wrong with what you believe.
Namely:
1. That sentence of Belcher is about the RLC lumped circuit of section 10. Read pages 15 and 16. It's not about the unlumpable Lewin ring.
2. The note of McDonald (it's not a paper, it's a note for his students) has been through many revisions, so you should also specify the date it was last updated. The most recent I have on my laptop says November 14, 2018. And he uses a definition of "voltage drop" that 'others' (namely the IEC) call 'scalar potential difference'. Therefore he is talking about the component of the voltage that is solely determined by the conservative electric field generated by the distribution of charge displaced by Eind. It's just that, and he says so on page 10, after formula (35). The scalar PD alone is insufficient to describe the physical system. In fact, you cannot even apply Ohm's law to that 'voltage drop' as he calls it. And he acknowledges that voltmeters do not measure that 'voltage drop' of his, but the path integral of the total electric field Etot (as Belcher says, as well).
Therefore, when stores will sell AC voltmeters that can read that scalar potential difference, that definition of his will come very handy. Till then, a lot of people prefer to use actual voltage, the one that can be measured by voltmeters and that is path-dependent. It is also much easier to treat.
3. By reading your thread with ThinkFat for the video "The Lewin loop inside an iron core - KVL still holds" it appears to me you have problems with basic electromagnetism.
You say con can "correctly lump" the circuit, but Lewin's ring is not lumpable.
You also seem to think that if your "volt meter leads do not cut through any changing magnetic fields [...], according to Faraday's law [...] there will be no voltage induced along my volt meter leads".
Do you really think that in order to induce a voltage, the conductors need to pass through the variable magnetic field region?
Is that the reason you want to drill a hole into the toroidal core?LOL Didn't you see the laughing face emoticons after that statement?
You also seem anxious about looking inside a transformer.It was a half-turn-on-a-toroid joke, man.
But that is the crux of the problem: Lewin's ring has placed two resistor inside the coil of a single turn transformer, creating a circuit that cannot be model with a lumped component.
Continuously variable variacs have been around forever - I've got one, real pretty, all silver plated, you turn the knob, and the wiper slides or rolls along the winding providing a movable tap at any of an infinite number of positions, limited only by the smoothness of the winding wire and the wiper roller.
Dr. McDonald said "Lewin's circuit is within the range of applicability of Kirchhoff's loop equations, which can be used to predict measurements by the 'voltmeters' in the experiment. "
You said you have no degrees and you're no math wiz.
Probably you didn't read the entire paper by McDonald, or if you did, you didn't understand it.
What he says is that, specifically for Lewin's circuit, it is possible to consider the EMF as a generator element of an equivalent circuit and still apply KVL EQUATIONS. Which is true.
But he stresses that this EMF is nowhere to be found with voltmeters in the circuit.
In Lewin’s example, the magnetic flux in the primary solenoid may well be within a small coil, but the secondary consists of only a single “turn”, so the associated inductive EMF is not well localized, but rather is distributed around the entire secondary loop. Then, since inductive EMF’s are associated with a vector potential, rather than a scalar potential, it can be misleading to interpret the inductive EMF as related to a “voltage”.
Lewin's beef is that people read that you can use KVL EQUATIONS to calculate the voltage across the resistors and try to find this EMF with voltmeters. You'll never find it.
People say that the voltages are in the wires. McDonald denies that. It's all over the circuit, and it is not a voltage. So voltmeters won't measure it. (In other words, this circuit is "unlumpable", and modeling it so as to make KVL work is just a math trick).
MacDonald says more.
Kirchhoff’s (extended) loop equation (1) does not apply to all possible circuits, and gives a poor description of circuits whose size is not small compared to relevant wavelengths, in which effects of radiation and retardation can be important. Examples such as Lewin’s in which the self inductance of the entire loop could be important must be treated with care.
So Kirchhoff's law doesn't always hold, does it?
He calculates and confirm that the two voltmeters in Lewin's experiment will show two different voltages even though connected to the same points in the circuit and then declares:
These results were validated by experiment during Lewin’s lecture demonstration.
Quote"In this sense, KVL holds, as argued by Mehdi Sadaghdar ..."
In what sense? Have you read the whole paper? He explicitly said that the voltage through an inductor is zero. Of course it is! It's just a piece of wire! But across the terminals of the inductor it is defined by its inductance (path dependence of voltage). And IN THIS SENSE, KVL holds. Which is true.
Quote"In this sense, KVL holds, as argued by Mehdi Sadaghdar ..."...
He explicitly said that the voltage through an inductor is zero.
...
And here we come to the Mehdi problem.
Mehdi claims that KVL ALWAYS holds. Which is not true.
He claims that Belcher agrees with him. He doesn't.
Belcher says KVL only holds for specific conditions. He says that Lewin is wrong and invokes McDonald. MacDonald doesn't say Lewin is wrong anywhere in his paper.
His argument is because he thinks that Lewin presented his circuit as a paradox that cannot be solved in the confines of Kirchhoff's equations. He shows it actually can. But in fact there's no paradox--that's Lewin's argument--when you realize the circuit is immersed in a non-conservative field, which is a much broader concept, that allows you to understand the problems to which McDonald says Kirchhoff's equations can't be applied.
Mehdi claims the voltages are in the wires, that Lewin doesn't know how to probe his circuit and many other irrational and nonfactual assertions. We just can't accept that.
...
PS: this would be a brilliant experiment: Use a split core with different permeability in each of the toroids, so that the flux is no longer evenly split. I wonder if the voltages would still add up ;)
Thank you for the invite here my friend!
And yes, the two toroids are slightly different from eachother. They actually really are two toroids in this particular transformer, each made from a looong strip of sheet metal wound up, and there are two of them in there, butted up.
And evidently, one has a little more iron to it because it has more voltage across it.
But regardless, the sum still adds up to "zero." (within the resolution limitation of my volt meter.)
However, if you would like, I would be glad to do an experiment literally with two different toroids which are of significantly different sizes, and do the same test to show you that even then, all the voltages add up to zero going clockwise around the loop.
Would that be meaningful to you? Do you think the voltage would no longer add up to zero?
Welcome to our little "Understanding Faradays' Law" support group. Please have a seat....
PS: this would be a brilliant experiment: Use a split core with different permeability in each of the toroids, so that the flux is no longer evenly split. I wonder if the voltages would still add up ;)
Thank you for the invite here my friend!
And yes, the two toroids are slightly different from eachother. They actually really are two toroids in this particular transformer, each made from a looong strip of sheet metal wound up, and there are two of them in there, butted up.
And evidently, one has a little more iron to it because it has more voltage across it.
But regardless, the sum still adds up to "zero." (within the resolution limitation of my volt meter.)
However, if you would like, I would be glad to do an experiment literally with two different toroids which are of significantly different sizes, and do the same test to show you that even then, all the voltages add up to zero going clockwise around the loop.
Would that be meaningful to you? Do you think the voltage would no longer add up to zero?
The voltages would still add up, I give you that. My mistake, I wasn't thinking straight.
But doesn't it feel odd how suddenly half of the Lewin Loop in your experiment has a vastly different voltage "across" the same red wire than before? Because the Lewin Loop, and also the yellow reference loop still experience the same flux as before (of course presuming the total magnetic flux didn't change).
And I have another thought experiment for you: what if you replaced the two resistors with just wires, what would you measure around the loop?
I can actually predict it: the voltage across the two wires replacing the resistors would read "zero", while across the other two, the red wires of your original experiment, you would still read roughly 100mV.
That is a little hard to explain with your claim that none of your probing wires "cross" any magnetic flux, right?
Instead of using my little red wires, I used a single length of 14AWG in a loop, and soldered the ends together with 3/4" overlap so I wouldn't have any contact resistance issues to worry about, like this: https://postimg.cc/nXD7ynQf
I cannot run it for very long because the wire starts getting hot.
However:
Measuring across where the red wires used to be gives about +50mv.
Measuring across where the resistors used to be gives about -50mv.
(NOTE: Signs are to indicate the phase! I was using an AC volt meter, but I also determined the phase.)
Measuring from two points exactly opposite on the copper ring gives about 0mv.
Yes, it's like "Ow My Balls!"* with some wires thrown in. But Lewin isn't any less of a showman.
Quote1. That sentence of Belcher is about the RLC lumped circuit of section 10. Read pages 15 and 16. It's not about the unlumpable Lewin ring.That's where I was quoting from. Wouldn't you say that he clearly describes that there are two different attributes, both of which use the unit volt, but one of which is always zero across an inductor and one which is what a volt meter reads, which is how KVL holds as argued by Mehdi?
He says "Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds) "
10. Another circuit
(https://i.postimg.cc/DZwxkkyJ/screenshot-3.png)
link to image: https://i.postimg.cc/DZwxkkyJ/screenshot-3.png (https://i.postimg.cc/DZwxkkyJ/screenshot-3.png)
The experiment above was not considered in the video, but I offer it up as an exercise for the reader. I have a “one-loop” inductor, with a capacitor and resistor, as shown, where I assume the self-magnetic field is only non-zero inside the loop. The battery is shown with the positive terminal down, which will result in a current flow counterclockwise around the circuit, giving a self-magnetic field out of the paper.
"And now I'm going to cause you some sleepless nights. And I'm going to attach here a voltmeter... And now I'm going to ask you what would this voltmeter show. And you'll probably say: 'well didn't you say that the integral of E dot dl through this wire is zero?' So you will think that V here is zero. But that's not true. You know what V is going to be? It's going to be + L di/dt."
Instead of using my little red wires, I used a single length of 14AWG in a loop, and soldered the ends together with 3/4" overlap so I wouldn't have any contact resistance issues to worry about, like this: https://postimg.cc/nXD7ynQf
I cannot run it for very long because the wire starts getting hot.
The wire getting hot means there's a significant contribution by Mr. Ohm and so we can no longer neglect him.
EDIT (sorry, I pushed the POST button to early)
QuoteHowever:
Measuring across where the red wires used to be gives about +50mv.
Measuring across where the resistors used to be gives about -50mv.
(NOTE: Signs are to indicate the phase! I was using an AC volt meter, but I also determined the phase.)
Measuring from two points exactly opposite on the copper ring gives about 0mv.
You get 50mV from the voltage drop due to the wire resistance, -100mV from the EMF in the volt meter loop, resulting in -50mV total.
You get 0mV across two opposite points on the loop, but only in one case, if your volt meter loop encloses a part of the core (linking the flux and having an induced EMF) and also the ohmic voltage drop exactly counters the EMF in the volt meter loop. But it will be path dependent, in any other case you will get a non-zero voltage reading.
(https://i.postimg.cc/jdTDgf6D/Screenshot-2021-11-16-at-12-06-04-Microsoft-Word-Faradays-Law-Mehdi-Dr-John-Belcher-on-Faradays-Law.png)
At 4:31 into the video, Mehdi draws the open circuit to the left above. There is no current flowing
because the curcuit is open. Let’s discuss this situation before we put the voltmeter into the circuit.
There will be zero electric field in the wires, because in the wires the induced electric field exactly
cancels the coulomb electric field, as we saw before.
But we will still see a charge accumulation on the ends of the wire, as shown in the schematic to the right above.
The upper end of the wire will be charged negatively and the lower end of the wire will be charged positively.
Moreover we can calculate the potential difference across the gap by using Faraday’s Law (which applies for
any open surface and its bounding contour, where or not there are any wires around. Going around the circle
counterclockwise gives us (l is the height of the gap)
(https://i.postimg.cc/QxFckh0C/Screenshot-2021-11-16-at-11-59-16-Microsoft-Word-Faradays-Law-Mehdi-Dr-John-Belcher-on-Faradays-Law.png)
If you want to reassure yourself that this electric field actually exists, make (https://i.postimg.cc/T1LhmYfX/Screenshot-2021-11-16-at-12-00-09-Microsoft-Word-Faradays-Law-Mehdi-Dr-John-Belcher-on-Faradays-Law.png) larger than the
breakdown voltage in air, about a million volts per meter, and you will see a spark across the gap that
proves that there is an electric field there, whether you put a voltmeter into the circuit or not.
Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds)
+V - IR - Q/C - L(dI/dt) = 0, but the first three terms here are the -∫E.dl through the various circuit
elements, and the last term has nothing to do with the -∫E.dl through the inductor, which is zero.
Quote1. That sentence of Belcher is about the RLC lumped circuit of section 10. Read pages 15 and 16. It's not about the unlumpable Lewin ring.
That's where I was quoting from. Wouldn't you say that he clearly describes that there are two different attributes, both of which use the unit volt, but one of which is always zero across an inductor and one which is what a volt meter reads, which is how KVL holds as argued by Mehdi?
He says "Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds) "
Ok, let me join the dots for you.
About that sentence by Belcher
You already posted the two relevant pages of Belcher's note. Let me show you that the partial sentence you keep repeating ("In this sense, KVL holds as argued by Mehdi Sagadhdar, but..." - oh, no! You stop right before the 'but') is not about the unlumpable Lewin's ring, but another, lumpable, circuit. You need to read carefully, lest you mistake similar words, like "many" with "any", or something like that.
The famous sentence appears in section 11 on page 16, but it is related to a discussion that began in section 10, on page 15.
Source: Belcher's note available on Mehdi's YT channel. Let's see what section 10 is about, first.Quote10. Another circuit
([url]https://i.postimg.cc/DZwxkkyJ/screenshot-3.png[/url])
link to image: [url]https://i.postimg.cc/DZwxkkyJ/screenshot-3.png[/url] ([url]https://i.postimg.cc/DZwxkkyJ/screenshot-3.png[/url])
The experiment above was not considered in the video, but I offer it up as an exercise for the reader. I have a “one-loop” inductor, with a capacitor and resistor, as shown, where I assume the self-magnetic field is only non-zero inside the loop. The battery is shown with the positive terminal down, which will result in a current flow counterclockwise around the circuit, giving a self-magnetic field out of the paper.
At the top of p. 15, he writes
([url]https://i.postimg.cc/vTphV47f/screenshot-4.png[/url])
[url]https://i.postimg.cc/vTphV47f/screenshot-4.png[/url] ([url]https://i.postimg.cc/vTphV47f/screenshot-4.png[/url])
Take note of the equation, You will see it repeated shortly. For the time being, let's look at the other picture:
([url]https://i.postimg.cc/ZqCLVPfp/screenshot-5.png[/url])
[url]https://i.postimg.cc/ZqCLVPfp/screenshot-5.png[/url] ([url]https://i.postimg.cc/ZqCLVPfp/screenshot-5.png[/url])
Oh, look: same circuit, same test points to which attach the probes and different voltages depending on whether the voltmeter is on the left or on the right of the loop. I wonder where I have ever seen that before.
Oh yes, Lewin's ring. There is a difference though: Lewin's ring is not lumpable, while this RLC circuit with lumped R, L and C component is lumpable.
How so? What you need to do to consider it lumped is to devise a circuit path that DOES NOT CONTAIN the changing magnetic flux region in its interior (technically, we should say that the closed circuit loop does not cut any net flux - but in 2D it's easier to say what I just wrote). If you can do that, then all voltages along any path you could imagine in the area enclosed by your circuit path, will be path independent (they will only depend on endpoints).
How can you find such a circuit path? Easy: instead of having the circuit path following the coil's filament, we consider the circuit path jumping in the space between the coil terminals. As explained by Feynman, shown by Hayt (posted an excerpt just a few pages above in this thread), detailed by Ramo Whinnery and VanDuzer, exemplified by Purcell, and Haus and Melcher, and Faria, and in the published papers by Romer, Roche, Nicholson, and on and on and on... now you can apply KVL to your freshly lumped circuit and be happy. It's fake, because voltage will still in general depend on path, but in our little bubble we can pretend it doesn't. In that sense, in that little safe space we just cut out from the rest of the real world, KVL holds.
Let me rephrase it: if you can hide the changing magnetic flux inside a lumped component, and you do not look inside it (meaning: your circuit path does not go inside those forbidden zone components and thus it is impossible to go around the dB/dt region) then the "amended" KVL holds.
Yet, whenever you consider circuit paths that go around the magnetic region, -pouff- the dream shatters. For example, if your circuit path consists of only one inductor and the jump at its terminal, you will see KVL die in the definition itself of voltage across the terminals of the lumped inductor. If you accept the definition of voltage as (minus) the path integral of the total electric field (such as that given by the IEC), the following paragraph says just that
([url]https://i.postimg.cc/5y3vxj7f/screenshot-6.png[/url])
[url]https://i.postimg.cc/5y3vxj7f/screenshot-6.png[/url] ([url]https://i.postimg.cc/5y3vxj7f/screenshot-6.png[/url])
i.e. you have a voltage -Ldi/dt across the terminals of the (self-)inductor, but zero voltage along the filament of its coil. Voltage referred to the same points A and B is different depending on the particular path you refer it to. Exactly what Lewin says in his video "Kirchhoff law is for the birds=https://youtu.be/LzT_YZ0xCFY ([url]http://Kirchhoff[/url] law is for the birds=https://youtu.be/LzT_YZ0xCFY)", at minute 33:Quote"And now I'm going to cause you some sleepless nights. And I'm going to attach here a voltmeter... And now I'm going to ask you what would this voltmeter show. And you'll probably say: 'well didn't you say that the integral of E dot dl through this wire is zero?' So you will think that V here is zero. But that's not true. You know what V is going to be? It's going to be + L di/dt."
Oh, look! Belcher and Lewin are saying the very same thing.
Anyway, let's go back to Belcher's note and the infamous sentence KVL keep waving like a victory flag. To show that Belcher was talking about the lumped RLC circuit, here is the rest of page 15
([url]https://i.postimg.cc/dV77fWYs/screenshot-9.png[/url])
[url]https://i.postimg.cc/dV77fWYs/screenshot-9.png[/url] ([url]https://i.postimg.cc/dV77fWYs/screenshot-9.png[/url])
Do you recognize the equation +V - IR - Q/C - Ldi/dt = 0 ? It's the equation for the series lumped RLC circuit.
This part of Belcher's note is about the series lumped RLC circuit where L is the self inductance. NOT the unlumpable LEWIN's RING (where, incidentally but not importantly, the self inductance is negligible). It is about the different approach IN LUMPED CIRCUIT THEORY between properly applying Faraday (using a circuit path the goes through the filament and accounting for the magnetic flux intercepted by the path: 5 + 3 + 0 = 8 ) and using the 'amended version of KVL' (using a circuit path that jumps at the inductor terminals and pretending -L di/dt is a potential difference to save KVL: 5 + 3 - 8 = 0).
One can still save KVL for lumped circuits by bringing the rhs (the surface integral of B.dS) to the left side (and pretending it is a path integral of E.dl).
The trick works ONLY IF you can devise a circuit path that DOES NOT contain the variable magnetic flux region.
You can do it for the lumpable RLC circuit.
And this is the "amended", or "modified", or "extended" or "new" KVL that is so very often badly explained in high school and in first, second year introductory uni books (they use the 5 + 3 - 8 = 0 formalism that erroneously lead students to think there is a voltage buildup in the wires of a coil - Lewin says that "the physics stinks").
You CANNOT DO IT for Lewin's ring.
Why? Because it is required that the two resistor be on the opposite sides of the variable magnetic region. So, your circuit path is BY DEFINITION required to contain the magnetic flux region. The circuit is unlumpable.
([url]https://i.stack.imgur.com/HXv9x.jpg[/url])
source: [url]https://electronics.stackexchange.com/questions/551244/what-would-a-voltmeter-measure-if-you-had-an-electromotive-force-generated-by-a/551428#551428[/url] ([url]https://electronics.stackexchange.com/questions/551244/what-would-a-voltmeter-measure-if-you-had-an-electromotive-force-generated-by-a/551428#551428[/url])
And as such, it cannot be properly modeled by lumped transformer models, without changing the true nature of the system (i.e. without introducing jumps in voltage whenever you encounter one of these lumped coils).
([url]https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png[/url])
source: [url]https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png[/url] ([url]https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png[/url])
In order to model it with two or four lumped coils, the magnetic field region must be splitted to accomodate a circuit path that does not include any of it. I used the same 'stellated' path style used by Feynman in figure 22-9 at page 22-7 of his second volume of lectures.
Some ask: "don't you see the transformer?" Well, when you are inside the coil, when your circuit path go around the dB/dt coil you no longer have the luxury of using a lumped component model (the secondary of a transformer to which you can apply KVL) for the coil. You have an unlumpable circuit and you need to deal with it accordingly: ditch KVL and use Faraday.
I have a crystal ball that almost never fails me. It is now telling me that, despite being shown here that Belcher was not talking about Lewin's ring when he wrote that sentence, you will nevertheless keep use that very sentence in the future to show that Belcher agrees with Mehdi on Lewin being wrong on the Lewin ring. Just like Mehdi pretendend both Belcher and Feynman agrees with him on all the line, including Lewin's ring. By using your terminology: he is either "clueless", or "ignorant" or "not being honest". In any case: disappointing.
And I have not even mentioned the other note written by Belcher many years ago with Lewin, where they discuss the RL circuit and the "Kirchhoff second law modified for inductors", saying (regarding the 5 + 3 - 8 = 0 formalism)
([url]https://i.postimg.cc/zGMhDsjH/screenshot-7.png[/url])
source: Lewin and Belcher note for 802.11, updated by Lewin to add pointer to Giancoli and to his lecture.
snippet url: [url]https://i.postimg.cc/zGMhDsjH/screenshot-7.png[/url] ([url]https://i.postimg.cc/zGMhDsjH/screenshot-7.png[/url])
which also contains the treatment of the ring made of uniform resistive material and of two resistive halves in a variable magnetic field. Even there, you will see that Belcher's and Lewin's view are the same.
Next stop: a bit more detail on McDonald's note.
(but first, a few fun posts )
But to clarify two things, are we in agreement then that in cases where an inductor or transformer output has it's dB/dt contained entirely within itself, it can be perfectly lumped as an element for the sake of KVL?
So I don't need to keep arguing with people about whether my KVL in an iron core transformer is valid?
Also, if I understand correctly, you're saying that my Lewin Clock would be lumpable only at the resistors because that's the only place I can measure a voltage difference without running my leads around an area of dB/dt,
Dr. Belcher writes:Quote(https://i.postimg.cc/jdTDgf6D/Screenshot-2021-11-16-at-12-06-04-Microsoft-Word-Faradays-Law-Mehdi-Dr-John-Belcher-on-Faradays-Law.png)And everybody stops reading there and declares that a transformer does not have a voltage output.
At 4:31 into the video, Mehdi draws the open circuit to the left above. There is no current flowing
because the curcuit is open. Let’s discuss this situation before we put the voltmeter into the circuit.
There will be zero electric field in the wires, because in the wires the induced electric field exactly
cancels the coulomb electric field, as we saw before.
But to clarify two things, are we in agreement then that in cases where an inductor or transformer output has it's dB/dt contained entirely within itself, it can be perfectly lumped as an element for the sake of KVL?
So I don't need to keep arguing with people about whether my KVL in an iron core transformer is valid?
Oh, for Stokes' sakes!
No, you can't use KVL on the circuit running around a core.
Let's say I have a toroid transformer, or an EI transformer. It's got a primary and two secondaries.
The two secondaries are individual separate isolated output windings.
Each secondary produces 100mV AC RMS 60hz.
That's all, just an ordinary power transformer, two secondaries each producing 100mV AC RMS 60hz.
Can I consider these two 100mV AC RMS 60hz signals to be lumped element voltage sources coming from a self contained black box, and may I use them as lumped elements to form a loop with the two secondaries and two resistors all in series, and will KVL hold for this setup?
Let's say I have a toroid transformer, or an EI transformer. It's got a primary and two secondaries.
The two secondaries are individual separate isolated output windings.
Each secondary produces 100mV AC RMS 60hz.
That's all, just an ordinary power transformer, two secondaries each producing 100mV AC RMS 60hz.
Can I consider these two 100mV AC RMS 60hz signals to be lumped element voltage sources coming from a self contained black box, and may I use them as lumped elements to form a loop with the two secondaries and two resistors all in series, and will KVL hold for this setup?
You mean two secondaries in series? Sure, it's the first figure in the bottom row. The one that says "two secondaries in series".
And if you want to use four secondaries, second picture in the bottom row. The one that says "four secondaries in series".
(https://i.postimg.cc/JnvnsgYG/Spot-the-differences.png)
https://i.postimg.cc/JnvnsgYG/Spot-the-differences.png
Maybe the image is too small and you didn't see it, in my previous post?
... But Lewin isn't any less of a showman. ...
Yes, it's like "Ow My Balls!"* with some wires thrown in. But Lewin isn't any less of a showman.
That's where the similarities between the two end. Every reputable author says the same thing about trying to apply KVL to a circuit subjected to a non-conservative field: caveat emptor, if you try to find the inductive EMF in the circuit as a voltage you'll come a gutser. But, people shrug and don't pay attention. Lewin does the same the other authors do, only that he goes one step further and asks his students to explain WHY exactly you can't find the "missing" "voltage". Wouldn't expect less from an MIT-quality lecture.
Mehdi does differently. He says that this "voltage" is really somewhere in the circuit (sometimes in the wire, sometimes in the resistors) and through some kind of clever technique you will be able to find it. Those who believe his false claims set out to devise all kinds of pseudo-scientific and contradictory explanations and "experiments" to try to confirm the word of their idol.
But Mehdi does worse. He divides the community and incites people against each other, all in the name of a polemic with the only intent of increasing his viewership.
Fortunately, there are courageous people who are turning this into an opportunity to debunk this bunk and introduce people to the tried and tested concepts behind the electromagnetic phenomenon.
My prediction was under the assumption that Mr. Ohm can be ignored. Obviously he wasn't agreeing with that. But that doesn't invalidate my point.Instead of using my little red wires, I used a single length of 14AWG in a loop, and soldered the ends together with 3/4" overlap so I wouldn't have any contact resistance issues to worry about, like this: https://postimg.cc/nXD7ynQf
I cannot run it for very long because the wire starts getting hot.
The wire getting hot means there's a significant contribution by Mr. Ohm and so we can no longer neglect him.
EDIT (sorry, I pushed the POST button to early)
haha yeah, I saw your initial post and was tempted to reply "I love the way you drive home your point... But what is it? hahaha" but I figured you weren't done so I'd let you finish :-DDQuoteHowever:
Measuring across where the red wires used to be gives about +50mv.
Measuring across where the resistors used to be gives about -50mv.
(NOTE: Signs are to indicate the phase! I was using an AC volt meter, but I also determined the phase.)
Measuring from two points exactly opposite on the copper ring gives about 0mv.
You get 50mV from the voltage drop due to the wire resistance, -100mV from the EMF in the volt meter loop, resulting in -50mV total.
You get 0mV across two opposite points on the loop, but only in one case, if your volt meter loop encloses a part of the core (linking the flux and having an induced EMF) and also the ohmic voltage drop exactly counters the EMF in the volt meter loop. But it will be path dependent, in any other case you will get a non-zero voltage reading.
But your prediction was unambiguously wrong. Remember, you predicted that there would be 0v across the wires replacing the resistors, and about 100mv measured 'around the ends' where the red wires used to be.
What gives? Your odds aren't very good here. First you suggested that maybe vastly different sizes of toroids in my EI-Core configuration might not sum to zero in the "KVL in an iron core" setup. You were wrong, sure, everyone makes a mistake.The odds are entirely in my favor, though you are yet unable to see it.
Now you've made yet another prediction, you said I'd get around 0,100,0,100 mv on my shorted winding. I got around 50,50,50,50 which is not even arguably close to what you predicted.
Also, above you say that "But it will be path dependent." What will be path dependent? What path? The path of my volt meter leads? Or the path of the shorted winding?
By the way, have you read Dr. Belchers writup on the subject yet?
He goes over the idea of an unloaded transformer having voltage.
He basically cites Faraday's law and says that if you want to reassure yourself that the electric field actually exists, just increase the output voltage of the transformer to where it jumps an arc. He says you will see a spark and that PROVES (his word, my emphasis) that there is an electric field there, whether you put a volt meter onto the circuit or not.
So why the tarzan can't Kirchhoff's VOLTAGE Law be applied to a transformer secondary as a lumped element?
So what is this whole debacle about? Is it about whether a transformer output has a voltage because "There will be zero electric field in the wires, because in the wires the induced electric field exactly cancels the coulomb electric field?"
Look at what Dr. Belcher says:Quote
Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds)
+V - IR - Q/C - L(dI/dt) = 0, but the first three terms here are the -∫E.dl through the various circuit
elements, and the last term has nothing to do with the -∫E.dl through the inductor, which is zero.
Do you see that last term, which Belcher says has NOTHING (his word, my emphasis) to do with the first 3 terms?
Do you see that last term? That's Faraday's law.
I think you're ignoring Faraday's law, which is, according to Belcher, part of the deal here.
Of course if you ignore Faraday's law, then you're going to say that there's no voltage on the output winding of a transformer, because Faradays law is the term which describes the induced voltage difference across the ends of the winding!
Am I all wrong? What gives? What do you take Belcher to be saying here?
Thank you.
Quote1. That sentence of Belcher is about the RLC lumped circuit of section 10. Read pages 15 and 16. It's not about the unlumpable Lewin ring.That's where I was quoting from. Wouldn't you say that he clearly describes that there are two different attributes, both of which use the unit volt, but one of which is always zero across an inductor and one which is what a volt meter reads, which is how KVL holds as argued by Mehdi?
He says "Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds) "
Ok, let me join the dots for you.
About that sentence by Belcher
You already posted the two relevant pages of Belcher's note. Let me show you that the partial sentence you keep repeating ("In this sense, KVL holds as argued by Mehdi Sagadhdar, but..." - oh, no! You stop right before the 'but') is not about the unlumpable Lewin's ring, but another, lumpable, circuit.
The famous sentence appears in section 11 on page 16, but it is related to a discussion that began in section 10, on page 15.
Source: Belcher's note available on Mehdi's YT channel. Let's see what section 10 is about, first.Quote10. Another circuit
(https://i.postimg.cc/DZwxkkyJ/screenshot-3.png)
link to image: https://i.postimg.cc/DZwxkkyJ/screenshot-3.png (https://i.postimg.cc/DZwxkkyJ/screenshot-3.png)
The experiment above was not considered in the video, but I offer it up as an exercise for the reader. I have a “one-loop” inductor, with a capacitor and resistor, as shown, where I assume the self-magnetic field is only non-zero inside the loop. The battery is shown with the positive terminal down, which will result in a current flow counterclockwise around the circuit, giving a self-magnetic field out of the paper.
At the top of p. 15, he writes
(https://i.postimg.cc/vTphV47f/screenshot-4.png)
https://i.postimg.cc/vTphV47f/screenshot-4.png (https://i.postimg.cc/vTphV47f/screenshot-4.png)
Take note of the equation, You will see it repeated shortly. For the time being, let's look at the other picture:
(https://i.postimg.cc/ZqCLVPfp/screenshot-5.png)
https://i.postimg.cc/ZqCLVPfp/screenshot-5.png (https://i.postimg.cc/ZqCLVPfp/screenshot-5.png)
Oh, look: same circuit, same test points to which attach the probes and different voltages depending on whether the voltmeter is on the left or on the right of the loop. I wonder where I have ever seen that before.
Oh yes, Lewin's ring. There is a difference though: Lewin's ring is not lumpable, while this RLC circuit with lumped R, L and C component is lumpable.
How so? What you need to do to consider it lumped is to devise a circuit path that DOES NOT CONTAIN the changing magnetic flux region in its interior (technically, we should say that the closed circuit loop does not cut any net flux - but in 2D it's easier to say what I just wrote). If you can do that, then all voltages along any path you could imagine in the area enclosed by your circuit path, will be path independent (they will only depend on endpoints).
How can you find such a circuit path? Easy: instead of having the circuit path following the coil's filament, we consider the circuit path jumping in the space between the coil terminals. As explained by Feynman, shown by Hayt (posted an excerpt just a few pages above in this thread), detailed by Ramo Whinnery and VanDuzer, exemplified by Purcell, and Haus and Melcher, and Faria, and in the published papers by Romer, Roche, Nicholson, and on and on and on... now you can apply KVL to your freshly lumped circuit and be happy. It's fake, because voltage will still in general depend on path, but in our little bubble we can pretend it doesn't. In that sense, in that little safe space we just cut out from the rest of the real world, KVL holds.
Let me rephrase it: if you can hide the changing magnetic flux inside a lumped component, and you do not look inside it (meaning: your circuit path does not go inside those forbidden zone components and thus it is impossible to go around the dB/dt region) then the "amended" KVL holds.
Yet, whenever you consider circuit paths that go around the magnetic region, -pouff- the dream shatters. For example, if your circuit path consists of only one inductor and the jump at its terminal, you will see KVL die in the definition itself of voltage across the terminals of the lumped inductor. If you accept the definition of voltage as (minus) the path integral of the total electric field (such as that given by the IEC),
the following paragraph says just that
(https://i.postimg.cc/5y3vxj7f/screenshot-6.png)
https://i.postimg.cc/5y3vxj7f/screenshot-6.png (https://i.postimg.cc/5y3vxj7f/screenshot-6.png)
i.e. you have a voltage -Ldi/dt across the terminals of the (self-)inductor, but zero voltage along the filament of its coil. Voltage referred to the same points A and B is different depending on the particular path you refer it to. Exactly what Lewin says in his video "Kirchhoff law is for the birds=https://youtu.be/LzT_YZ0xCFY (http://Kirchhoff law is for the birds=https://youtu.be/LzT_YZ0xCFY)", at minute 33:Quote"And now I'm going to cause you some sleepless nights. And I'm going to attach here a voltmeter... And now I'm going to ask you what would this voltmeter show. And you'll probably say: 'well didn't you say that the integral of E dot dl through this wire is zero?' So you will think that V here is zero. But that's not true. You know what V is going to be? It's going to be + L di/dt."
Oh, look! Belcher and Lewin are saying the very same thing.
Anyway, let's go back to Belcher's note and the infamous sentence KVL keep waving like a victory flag. To show that Belcher was talking about the lumped RLC circuit, here is the rest of page 15
(https://i.postimg.cc/dV77fWYs/screenshot-9.png)
https://i.postimg.cc/dV77fWYs/screenshot-9.png (https://i.postimg.cc/dV77fWYs/screenshot-9.png)
Do you recognize the equation +V - IR - Q/C - Ldi/dt = 0 ? It's the equation for the series lumped RLC circuit.
This part of Belcher's note is about the series lumped RLC circuit where L is the self inductance. NOT the unlumpable LEWIN's RING (where, incidentally but not importantly, the self inductance is negligible). It is about the different approach IN LUMPED CIRCUIT THEORY between properly applying Faraday (using a circuit path the goes through the filament and accounting for the magnetic flux intercepted by the path: 5 + 3 + 0 = 8 ) and using the 'amended version of KVL' (using a circuit path that jumps at the inductor terminals and pretending -L di/dt is a potential difference to save KVL: 5 + 3 - 8 = 0).
One can still save KVL for lumped circuits by bringing the rhs (the surface integral of B.dS) to the left side (and pretending it is a path integral of E.dl).
The trick works ONLY IF you can devise a circuit path that DOES NOT contain the variable magnetic flux region.
You can do it for the lumpable RLC circuit.
And this is the "amended", or "modified", or "extended" or "new" KVL that is so very often badly explained in high school and in first, second year introductory uni books (they use the 5 + 3 - 8 = 0 formalism that erroneously lead students to think there is a voltage buildup in the wires of a coil - Lewin says that "the physics stinks").
You CANNOT DO IT for Lewin's ring.
Why? Because it is required that the two resistor be on the opposite sides of the variable magnetic region. So, your circuit path is BY DEFINITION required to contain the magnetic flux region. The circuit is unlumpable.
(https://i.stack.imgur.com/HXv9x.jpg)
source: https://electronics.stackexchange.com/questions/551244/what-would-a-voltmeter-measure-if-you-had-an-electromotive-force-generated-by-a/551428#551428 (https://electronics.stackexchange.com/questions/551244/what-would-a-voltmeter-measure-if-you-had-an-electromotive-force-generated-by-a/551428#551428)
And as such, it cannot be properly modeled by lumped transformer models, without changing the true nature of the system (i.e. without introducing jumps in voltage whenever you encounter one of these lumped coils).
(https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png)
source: https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png (https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png)
In order to model it with two or four lumped coils, the magnetic field region must be splitted to accomodate a circuit path that does not include any of it. I used the same 'stellated' path style used by Feynman in figure 22-9 at page 22-7 of his second volume of lectures.
Some ask: "don't you see the transformer?" Well, when you are inside the coil, when your circuit path go around the dB/dt coil you no longer have the luxury of using a lumped component model (the secondary of a transformer to which you can apply KVL) for the coil. You have an unlumpable circuit and you need to deal with it accordingly: ditch KVL and use Faraday.
I have a crystal ball that almost never fails me. It is now telling me that, despite being shown here that Belcher was not talking about Lewin's ring when he wrote that sentence, you will nevertheless keep use that very sentence in the future to show that Belcher agrees with Mehdi on Lewin being wrong on the Lewin ring. Just like Mehdi pretendend both Belcher and Feynman agrees with him on all the line, including Lewin's ring. By using your terminology: he is either "clueless", or "ignorant" or "not being honest". In any case: disappointing.
And I have not even mentioned the other note written by Belcher many years ago with Lewin, where they discuss the RL circuit and the "Kirchhoff second law modified for inductors", saying (regarding the 5 + 3 - 8 = 0 formalism)
(https://i.postimg.cc/zGMhDsjH/screenshot-7.png)
source: Lewin and Belcher note for 802.11, updated by Lewin to add pointer to Giancoli and to his lecture.
snippet url: https://i.postimg.cc/zGMhDsjH/screenshot-7.png (https://i.postimg.cc/zGMhDsjH/screenshot-7.png)
which also contains the treatment of the ring made of uniform resistive material and of two resistive halves in a variable magnetic field. Even there, you will see that Belcher's and Lewin's view are the same.
Next stop: a bit more detail on McDonald's note.
(but first, a few fun posts )
My prediction was under the assumption that Mr. Ohm can be ignored. Obviously he wasn't agreeing with that. But that doesn't invalidate my point.Instead of using my little red wires, I used a single length of 14AWG in a loop, and soldered the ends together with 3/4" overlap so I wouldn't have any contact resistance issues to worry about, like this: https://postimg.cc/nXD7ynQf
I cannot run it for very long because the wire starts getting hot.
The wire getting hot means there's a significant contribution by Mr. Ohm and so we can no longer neglect him.
EDIT (sorry, I pushed the POST button to early)
haha yeah, I saw your initial post and was tempted to reply "I love the way you drive home your point... But what is it? hahaha" but I figured you weren't done so I'd let you finish :-DDQuoteHowever:
Measuring across where the red wires used to be gives about +50mv.
Measuring across where the resistors used to be gives about -50mv.
(NOTE: Signs are to indicate the phase! I was using an AC volt meter, but I also determined the phase.)
Measuring from two points exactly opposite on the copper ring gives about 0mv.
You get 50mV from the voltage drop due to the wire resistance, -100mV from the EMF in the volt meter loop, resulting in -50mV total.
You get 0mV across two opposite points on the loop, but only in one case, if your volt meter loop encloses a part of the core (linking the flux and having an induced EMF) and also the ohmic voltage drop exactly counters the EMF in the volt meter loop. But it will be path dependent, in any other case you will get a non-zero voltage reading.
But your prediction was unambiguously wrong. Remember, you predicted that there would be 0v across the wires replacing the resistors, and about 100mv measured 'around the ends' where the red wires used to be.
By "odds" I really meant that your batting average is pretty poor at this point.QuoteWhat gives? Your odds aren't very good here. First you suggested that maybe vastly different sizes of toroids in my EI-Core configuration might not sum to zero in the "KVL in an iron core" setup. You were wrong, sure, everyone makes a mistake.The odds are entirely in my favor, though you are yet unable to see it.
QuoteNow you've made yet another prediction, you said I'd get around 0,100,0,100 mv on my shorted winding. I got around 50,50,50,50 which is not even arguably close to what you predicted.
And I explained why. Besides you got 50, -50, 50, -50 around the loop, mind the phase, and I also explained why. Anyway, you should have gotten a total of 200mV around the inner loop, according to Mr. Faraday, and you didn't, this should make you think. But apparently it doesn't. The reason you're getting 0V is because you're neglecting to account for parts of the EMF in your setup. Had you probed correctly, the total around the inner wire loop would have been the expected 200mV,
QuoteAlso, above you say that "But it will be path dependent." What will be path dependent? What path? The path of my volt meter leads? Or the path of the shorted winding?
For the sake of your measurements, only the path of your voltmeter loops are relevant.QuoteBy the way, have you read Dr. Belchers writup on the subject yet?
He goes over the idea of an unloaded transformer having voltage.
He basically cites Faraday's law and says that if you want to reassure yourself that the electric field actually exists, just increase the output voltage of the transformer to where it jumps an arc. He says you will see a spark and that PROVES (his word, my emphasis) that there is an electric field there, whether you put a volt meter onto the circuit or not.
But the question was never if there's an electric field at the terminals of a transformer or not. You will always have an electric field at discontinuities around a loop.
I'll ignore some part of your quoting Dr. Belcher because what he writes there is undisputed.QuoteSo why the tarzan can't Kirchhoff's VOLTAGE Law be applied to a transformer secondary as a lumped element?
You can, but only as long the transformer can be completely regarded as a black box which is fully described by its datasheet values. However, in your experiment, you chose measurement paths that are inside the transformer and exposed to magnetic flux and thus this simplification is not valid.
QuoteSo what is this whole debacle about? Is it about whether a transformer output has a voltage because "There will be zero electric field in the wires, because in the wires the induced electric field exactly cancels the coulomb electric field?"
Look at what Dr. Belcher says:Quote
Thus with Feynman et al.’s definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds)
+V - IR - Q/C - L(dI/dt) = 0, but the first three terms here are the -∫E.dl through the various circuit
elements, and the last term has nothing to do with the -∫E.dl through the inductor, which is zero.
Do you see that last term, which Belcher says has NOTHING (his word, my emphasis) to do with the first 3 terms?
Do you see that last term? That's Faraday's law.
I think you're ignoring Faraday's law, which is, according to Belcher, part of the deal here.
Of course if you ignore Faraday's law, then you're going to say that there's no voltage on the output winding of a transformer, because Faradays law is the term which describes the induced voltage difference across the ends of the winding!
Am I all wrong? What gives? What do you take Belcher to be saying here?
Thank you.
Dr. Belcher says that if you want KVL to hold, you need to subtract the EMF in the loop. That's what I pointed out above: The EMF induced in your inner wire loop is 200mV, so if you sum up all the electric fields in the loop they should add up to the EMF. But in your case they added up to 0V, which is obviously wrong according to Dr. Belcher.
Are you talking about my EI-Core transformer with the two red secondary windings?
Because Sredni has said that an EI-Core transformer's secondary winding outputs qualify as black box because the dB/dt is contained (for all practical purposes) entirely inside the iron core.
Let's say The 100mv and 100mv is induced where the wire passes through the transformer core.And there's your error, right there. This is complete BS.
About that sentence by BelcherThe "but" doesn't have anything to do with it not being lumpable.
Let me show you that the partial sentence you keep repeating ("In this sense, KVL holds as argued by Mehdi Sagadhdar, but..." - oh, no! You stop right before the 'but') is not about the unlumpable Lewin's ring, but another, lumpable, circuit.
And I just re-read Belcher's writeup, and I think you're wrong in saying that "In this sense, KVL holds as argued by Mehdi" was said about the RLC circuit that Belchar shows.
"In this sense, KVL holds as argued by Mehdi Sagadhdar, but one must always remember that the voltage difference across the inductor is defined in a very different way compared to the voltage difference across the other three elements."
"...but one must always remember that the voltage difference across the inductor is defined in a very different way compared to the voltage difference across the other three elements."
If Belcher is talking about a loop topology that Mehdi didn't argue about, how then can Belcher say "As argued by Mehdi?" What did Belcher mean? "As Mehdi would have argued had he argued with a loop with a capacitor?"
[...]
Mehdi DID NOT argue for KVL on any loop with capacitor in it. So how can that be the one that "Mehdi argued" for?
[...]
What argument of Mehdi's is Belcher supporting?
"So you see that the voltage across both R1 and R2 is equal to the voltage across R1 plus the voltage across R2 which is the same voltage ACROSS the loop. "
"This shows that the voltage ACROSS the loop is not zero, unlike what we've thought, but is equal to Vr1 plus Vr2. The loop is the secondary of a transformer, with the primary being my coil."
"Dr. Lewin's model misses a transformer in the loop, with the voltage across the winding equal to Vr1 plus Vr2. KVL HOLDS"
"An excellent discussion of “electromotive force” (a terrible and misleading name) is given in the text by Griffiths, Introduction to Electrodynamics 4th Edition."
About that sentence by Belcher
Let me show you that the partial sentence you keep repeating ("In this sense, KVL holds as argued by Mehdi Sagadhdar, but..." - oh, no! You stop right before the 'but') is not about the unlumpable Lewin's ring, but another, lumpable, circuit.
The "but" doesn't have anything to do with it not being lumpable.
And I just re-read Belcher's writeup, and I think you're wrong in saying that "In this sense, KVL holds as argued by Mehdi" was said about the RLC circuit that Belchar shows.
See, I told you my crystal ball almost never fails me.
You really don't see it! Do you?
You read the sentenceQuote from: John Belcher"In this sense, KVL holds as argued by Mehdi Sagadhdar, but one must always remember that the voltage difference across the inductor is defined in a very different way compared to the voltage difference across the other three elements."
and just before the but, you go on a celebratory trip and shut down. And yet, the circuit it is referred to is the lumpable RLC circuit whose equation is just above. Let's see what the but says:Quote from: John Belcher"...but one must always remember that the voltage difference across the inductor is defined in a very different way compared to the voltage difference across the other three elements."
And what could possibly be the other three elements? Well, the generator, the resistor and the capacitor, of course. He is talking about a lumpable circuit that, once lumped, allows for KVL to be applied. That sentence, it is one sentence, is not about Lewin's ring. (Also because in Lewin's ring the inductance L is neglible and one could also perform the experiment using a falling magnet, thus eliminating the secondary coil and the related mutual inductance as well - but let's forget about this).Quote from: Jesse Gordon
If Belcher is talking about a loop topology that Mehdi didn't argue about, how then can Belcher say "As argued by Mehdi?" What did Belcher mean? "As Mehdi would have argued had he argued with a loop with a capacitor?"
[...]
Mehdi DID NOT argue for KVL on any loop with capacitor in it. So how can that be the one that "Mehdi argued" for?
[...]
What argument of Mehdi's is Belcher supporting?
Dang, you really nailed me, here.
If only if could find a part in Mehdi's first video where he considers a lumped circuit and applies the 'modified KVL' to it, and hopefully says something along the lines of "KVL holds"...
Oh, let see...
At 8:21 in his first video on the topic, Mehdi draws his conclusions about a LUMPABLE circuit. This one:
([url]https://i.postimg.cc/zBSSpd8x/screenshot.png[/url])
[url]https://i.postimg.cc/zBSSpd8x/screenshot.png[/url]
and he says:Quote from: Electroboom"So you see that the voltage across both R1 and R2 is equal to the voltage across R1 plus the voltage across R2 which is the same voltage ACROSS the loop. "
Like you and Bob, he cannot understand that voltage, being path dependent in the presence of variable magnetic fields, can have different values depending (doh!) on the path and he is stuck with the terminology used in lumped circuit theory (where we consider the voltage across the terminals). In this case, since we are in the presence of a variable magnetic field, voltage depends on path and in particular: the voltage ACROSS the loop is Vr1+Vr2, while the voltage ALONG the loop is zero.
But the way he put resistors on one side makes this a lumpable circuit. In fact, it can be lumped by considering a circuit path that jumps at the terminals so that there is no variable magnetic field enclosed by said path. If we look at the circuit this way, the only voltage we need to consider in our limited safe space of lumped circuit theory is the voltage ACROSS the loop, which is not zero.
But Mehdi is clearly oblivious of all this, and keeps thinking that there can be only one value for the voltage between two pointsQuote from: Electroboom"This shows that the voltage ACROSS the loop is not zero, unlike what we've thought, but is equal to Vr1 plus Vr2. The loop is the secondary of a transformer, with the primary being my coil."
Well, no shit, Sherlock! That is a lumpable circuit and as such it can be modeled with lumped components. And sure enough, he produces a LUMPED circuit model:
([url]https://i.postimg.cc/285FFFJx/screenshot-2.png[/url])
[url]https://i.postimg.cc/285FFFJx/screenshot-2.png[/url]
A model that exhibit a massive jump in voltage when you encounter the lumped symbol of the inductor. Lumped circuit theory can only model the jump in voltage at the terminals because you are not allowed to look inside the transformer, BUT the voltage ALONG the loop is still zero (or, to be precise, the negligible ohmic loss in copper).
Let's hear it straight from the horse's mouth. I mean, from Mehdi, at 8:41:Quote from: Electroboom"Dr. Lewin's model misses a transformer in the loop, with the voltage across the winding equal to Vr1 plus Vr2. KVL HOLDS"
Well, we have now established that Mehdi talked about a LUMPED circuit in his first video (even though he does not realize that it IS NOT Lewin's ring, which is unlumpable exactly because the resistors are required to be on the opposite sides of the magnetic flux region). And that he applied KVL to said lumped circuit (which we can do, in the 'modified' form. Too bad it is not Lewin's ring). And he also says "KVL holds"!
In lumped circuits, such as this one (which is NOT Lewin's ring, let me repeat it) and the series RLC circuit considered by Belcher at page 15, we can make Faraday's law look like it's KVL. We just need to take the surface integral on the right, change its sign and put it in the lhs.
What have we done, by doing so? We started with a formula that says the circulation of E is NOT zero (when the circuit path follows the filament of the coil and thus INCLUDES the variable dB/dt region) and by cutting away the part of path the follows the coil and replacing it with the jump at its terminals we ended up with a formula that says that the circulation of E is ZERO (because the modified circuit path now skips - DOES NOT INCLUDE - the variable dB/dt) region.
In this modified circuit - THAT DOES NOT INCLUDE THE dB/dt REGION - KVL holds in the sense intended by Mehdi, but the voltage ACROSS the inductor is the result of the application of Faraday's law and the exclusion of its filament from the circuit's path.
And this is the key: in order to pull this trick (which I call the 'amended KVL') you need to be able to find a circuit path that DOES NOT INCLUDE THE VARIABLE MAGNETIC REGION AT ITS INTERIOR. You can do it when you put both resistors on the same side of the ring. You CANNOT do it for Lewin's ring (because Lewin's ring is Lewin's ring ONLY IF THE RESISTORS ARE ON THE OPPOSITE SIDES OF THE VARIABLE MAGNETIC FIELD REGION AND THE CIRCUIT PATH INCLUDES THAT REGION).
Now try to focus:
You cannot exclude the variable magnetic flux region from the circuit path of a circuit that requires its circuit path to contain the variable magnetic flux region. No matter how hard you try.
Geometry matters, exactly because in the case of Lewin's ring we are talking about a non lumpable circuit whose circuit path is required to circle a variable magnetic region.
P.S
Incidentally, the last sentence in Belcher's note is the following:Quote from: John Belcher"An excellent discussion of “electromotive force” (a terrible and misleading name) is given in the text by Griffiths, Introduction to Electrodynamics 4th Edition."
and guess what? Griffiths has the Romer-Lewin ring in one of his problems. Problem 7.50 uses the same diagram as Romer's paper. And in the solution he states... "Notice that V1 != V2, even though they are connected to the same points!"
Well, it really looks like the reference Belcher suggests has been written by another of Lewin's minions.
QuoteAre you talking about my EI-Core transformer with the two red secondary windings?
Because Sredni has said that an EI-Core transformer's secondary winding outputs qualify as black box because the dB/dt is contained (for all practical purposes) entirely inside the iron core.
You're still completely disregarding that you have multiple loops in your EI-Core transformer experiment.
@Sredni isn't wrong, you just have troubles understanding what he said because you only hear what seems to suit your understanding. That's called "confirmation bias". That transfomer is a black box only at its terminals. But your measurements are not at its terminals.QuoteLet's say The 100mv and 100mv is induced where the wire passes through the transformer core.And there's your error, right there. This is complete BS.
QuoteAre you talking about my EI-Core transformer with the two red secondary windings?
Because Sredni has said that an EI-Core transformer's secondary winding outputs qualify as black box because the dB/dt is contained (for all practical purposes) entirely inside the iron core.
You're still completely disregarding that you have multiple loops in your EI-Core transformer experiment.
@Sredni isn't wrong, you just have troubles understanding what he said because you only hear what seems to suit your understanding. That's called "confirmation bias". That transfomer is a black box only at its terminals. But your measurements are not at its terminals.QuoteLet's say The 100mv and 100mv is induced where the wire passes through the transformer core.And there's your error, right there. This is complete BS.
To clarify regarding my EI-Core transformer, with the two red wires that pass through the core, are you saying that if I connected my volt meter leads across the ends of one of those red wires, are you saying that I could change my reading by changing the path of the volt meter leads as I moved them around the outside of the transformer?
Make another prediction. I got an EI-Core. I got a volt meter. I can pass a wire through one side, the other side, or both sides if you like.
Tell me where I should run the secondary turn wire, where I should connect my volt meter leads, and what I should do to witness this alleged path-dependence.
I think you're wrong. Because the dB/dt is contained "entirely" within the iron core, changing the path of the leads external to the core can make no difference in measured voltaged because it can make no difference in the quantity of area of enclosing dB/dt, because in order to change the enclosed area of dB/dt, the volt meter lead would have to physically pass through part of the iron core.
Exactly how would I witness this alleged path-dependence you assert?
PS: I object to Dr. Belchers statement that the EMF is a voltage difference.
One textbook that makes perfectly clear what the “voltage across the inductor” is is the textbook by
Feynman, Leighton, and Sands, The Feynman Lectures on Physics (Addison‐Wesley, Reading, MA 1964),
Vol II, p22‐2). In that textbook, the authors state explicitly that the -∫E.dl through the inductor must
be zero, and they define the voltage difference across the inductor (which the correctly identify as an
“electromotive force”, as ∮E.dl, which by Faraday’s Law is -L(dI/dt).
QuoteAre you talking about my EI-Core transformer with the two red secondary windings?
Because Sredni has said that an EI-Core transformer's secondary winding outputs qualify as black box because the dB/dt is contained (for all practical purposes) entirely inside the iron core.
You're still completely disregarding that you have multiple loops in your EI-Core transformer experiment.
@Sredni isn't wrong, you just have troubles understanding what he said because you only hear what seems to suit your understanding. That's called "confirmation bias". That transfomer is a black box only at its terminals. But your measurements are not at its terminals.QuoteLet's say The 100mv and 100mv is induced where the wire passes through the transformer core.And there's your error, right there. This is complete BS.
To clarify regarding my EI-Core transformer, with the two red wires that pass through the core, are you saying that if I connected my volt meter leads across the ends of one of those red wires, are you saying that I could change my reading by changing the path of the volt meter leads as I moved them around the outside of the transformer?
Make another prediction. I got an EI-Core. I got a volt meter. I can pass a wire through one side, the other side, or both sides if you like.
Tell me where I should run the secondary turn wire, where I should connect my volt meter leads, and what I should do to witness this alleged path-dependence.
I think you're wrong. Because the dB/dt is contained "entirely" within the iron core, changing the path of the leads external to the core can make no difference in measured voltaged because it can make no difference in the quantity of area of enclosing dB/dt, because in order to change the enclosed area of dB/dt, the volt meter lead would have to physically pass through part of the iron core.
Exactly how would I witness this alleged path-dependence you assert?
I apologize in advance for the quality of the drawing I whipped up in "Libreoffice Draw". I'm not really an artistic person and this stupid program isn't helping me be, either.
The attached drawing is a cross section through your EI-Core transformer with your Lewin-Loop.
"V1" is connected like you're probing right now. The volt meter reads 100mV or thereabouts.
"V2" is connected through a different path. I predict that the volt meter will read 0mV (or close to it).
There you go, knock yourself out.
(https://i.postimg.cc/Kvrx3DNc/Faraday.png)
...
That is NOT MY SETUP.
That is NOT MY SETUP.
See the attached screenshot from our discussion on YT, from the comment section of your video (saved "just in case").
That is NOT MY SETUP.
See the attached screenshot from our discussion on YT, from the comment section of your video (saved "just in case").
See the attached screenshot for your wiring setup. Clearly the red wires are inside the transformer. How on earth can you expect this not picking up an induced EMF when you just connect the probing leads on the outside, at both ends of the red wires? Do you really think you have to sling a wire around the core to create a "secondary"?
[...]
Mehdi talked about a LUMPED circuit in his first video (even though he does not realize that it IS NOT Lewin's ring, which is unlumpable exactly because the resistors are required to be on the opposite sides of the magnetic flux region). And that he applied KVL to said lumped circuit (which we can do, in the 'modified' form. Too bad it is not Lewin's ring). And he also says "KVL holds"!
[...]
Wow, all that and you didn't really answer my question. You never answer a question head-on, do you :-DD
Exactly what argument did Mehdi make that Belcher agreed with?
Are you saying that the ONLY Mehdi-argument that Belcher agreed with was a fully lumpable circuit?
[...]
Mehdi talked about a LUMPED circuit in his first video (even though he does not realize that it IS NOT Lewin's ring, which is unlumpable exactly because the resistors are required to be on the opposite sides of the magnetic flux region). And that he applied KVL to said lumped circuit (which we can do, in the 'modified' form. Too bad it is not Lewin's ring). And he also says "KVL holds"!
[...]
Wow, all that and you didn't really answer my question. You never answer a question head-on, do you :-DD
Exactly what argument did Mehdi make that Belcher agreed with?
Are you saying that the ONLY Mehdi-argument that Belcher agreed with was a fully lumpable circuit?
You are absolutely right. I committed an error. My bad.
I should have known better: if you are not capable of understanding a single sentence because it has a subordinate, there would be no hope that you could understand several paragraphs all in one post.
Let me use a single line. I'll try to simplify it for you:
Mehdi talked about a LUMPED circuit in his first video, he applied (extended) KVL to it and said "KVL holds".
Well, he was right. I too agree with Mehdi that KVL holds when applied to circuits with lumped inductors. And if you actually read my previous post you will see that I wrote the same sentence Belcher wrote. Am I agreeing with Mehdi on everything now?
Seriously dude, you really, really, really don't understand Faraday's law. You should look at surfaces, not segment of wire.
Jesse, you are aware that this is how you expect to measure the voltage in the conductors?
(https://i.postimg.cc/B61Zt8Nx/Bad-probing.jpg)
https://i.postimg.cc/B61Zt8Nx/Bad-probing.jpg
(it's a negative of a drawing on paper, therefore the filled probe tips are the black ones - I did not pay excessive attention at the signs but they should be right. Also I chose 100 mV for the central leg and 50 mV for the other two. And I did not care to look up the values for the resistor - fill them in, if you want)
Does it not strike you as strange that if you remove the ring, leaving only the one conductor you expect to measure the voltage of, you still measure half the EMF of the central leg (50 mV)?
Not a bit?
Moreover, you can slide the probes along the conductors and you would still always read the same voltages. Does it not strike you as curious that the voltage drop for the wires is the same whether you consider the full branch or one millimeter of conductor?
The left and right voltmeters form flux-free loops with the nearest resistor branches, and therefore measure the correct branch voltages.
...
I deleted your incoherent ranting.
You asked for an example how you would be able to "experience" the path dependence. I provided a drawing.
I predict that V1 will show 100mV, V2 will show 0V. What else are you asking? It is the same probing points, just connected to the volt meter through different paths. This is what "path dependent" is about.
The path going through V1 is linking the flux in the core, the path through V2 is not. V1 displays an EMF in the circuit going around one leg of the EI-Core, V2 displays just the voltage drop in the red wire according to Mr. Ohm, which will be (close to) 0V.
But your reaction shows quite clearly that you don't have the slightest idea how a transformer works, and what makes it work.
Really, this feels like discussing with a flatearther.
That is NOT MY SETUP.
See the attached screenshot from our discussion on YT, from the comment section of your video (saved "just in case").
See the attached screenshot for your wiring setup. Clearly the red wires are inside the transformer. How on earth can you expect this not picking up an induced EMF when you just connect the probing leads on the outside, at both ends of the red wires? Do you really think you have to sling a wire around the core to create a "secondary"?
Continuously variable variacs have been around forever - I've got one, real pretty, all silver plated, you turn the knob, and the wiper slides or rolls along the winding providing a movable tap at any of an infinite number of positions, limited only by the smoothness of the winding wire and the wiper roller.
Could you show a picture or a link? I've never seen a variac like that. I assume you mean a line-voltage variac?
Really, this feels like discussing with a flatearther.
Please don't say that. Don't think for a moment that the feeling isn't mutual.
...
I take it you are saying that my two red wires are not lumpable voltage sources...? Wouldn't this be evidenced by a change in volt meter reading by where I hung my volt meter leads OUTSIDE the transformer?
Questions:
Answering these will help me understand what you're trying to say.
1:If I pass my secondary through BOTH halves for a total of 200mv, will the secondary then be a lumpable voltage sources?
2: If instead of an EI-Core, I had a toroid, and I pass a wire through the center, would that secondary be lumpable?
3: If instead of an EI-Core, I had two nearly identical toroids with the primaries in series and the same number of primary turns on each, and I passed a secondary wire through each of the toroids, would those two outputs be lumpable voltage sources?
4: If instead of an EI-Core, I had two nearly identical toroids side by side like OO with the primary wound through both of them, and I passed a secondary wire through each of the toroids, would those two secondaries be lumpable voltage sources?
Questions:
Answering these will help me understand what you're trying to say.
1:If I pass my secondary through BOTH halves for a total of 200mv, will the secondary then be a lumpable voltage sources?
2: If instead of an EI-Core, I had a toroid, and I pass a wire through the center, would that secondary be lumpable?
3: If instead of an EI-Core, I had two nearly identical toroids with the primaries in series and the same number of primary turns on each, and I passed a secondary wire through each of the toroids, would those two outputs be lumpable voltage sources?
4: If instead of an EI-Core, I had two nearly identical toroids side by side like OO with the primary wound through both of them, and I passed a secondary wire through each of the toroids, would those two secondaries be lumpable voltage sources?
I cannot answer that. I have trouble understanding what actual geometry you are describing.
What do you mean by "passing a wire through each of the toroids"?
I think we need to go back to the basics of Faradays Law to align our mutual understanding.The EI-Core arrangement is already too complex. The EI geometry of the core allows for too many possibilities to shoot oneself in the foot and we should abandon it for the discussion.
A single toroid core and a setup like in the following video would be much easier.
Are you saying that the two red wires passing through the two halves of my transformer core are not lumpable voltage sources?
What do you mean by "passing a wire through each of the toroids"?
Oh dear. Ok. A toroidal transformer has exactly ONE opening in the core, as the core takes on the shape of a torus.
When you want to add a new secondary winding to a toroidal transformer, you thread that new secondary winding wire through that one hole in the center of the core, and voilà! you have a new secondary winding! If you want more turns to your new secondary, loop it through a few more times.
You seriously don't know what it means to pass a wire through a hole in a toroid? Should I have said "Thread it through?" or "Place the wire so that it follows a path through the hole in the toroidal transformer core?"I think we need to go back to the basics of Faradays Law to align our mutual understanding.The EI-Core arrangement is already too complex. The EI geometry of the core allows for too many possibilities to shoot oneself in the foot and we should abandon it for the discussion.
Dude, an EI-Core is not complex! It's just two toroids side by side with the primary windings in series!
If you call that complex I guess we're in trouble.
A single toroid core and a setup like in the following video would be much easier.
Since you understand a simple toroidal transformer, at least answer THAT one of my questions!
I'll repeat it and clarify it so you realize we're talking about transformers here:
2: If I had a toroid based transformer, and I pass a wire through the center of the toroid to form a new secondary,, would that new secondary be a lumpable black box voltage source for the sake of KVL?
With both sides feeling like they are debating flat earthers.
Really, this feels like discussing with a flatearther.
Please don't say that. Don't think for a moment that the feeling isn't mutual.
...
Lewin: KVL doesn't hold for circuits immersed in a non-conservative electric field, here is the theory to support this claim and here is the demonstration.
Lewin: KVL doesn't hold for circuits immersed in a non-conservative electric field, here is the theory to support this claim and here is the demonstration.What non-conservative electric field are you talking about?
I had no idea the KVL thing was raging on the forum again! :popcorn:This must be the longest thread on the AmpHour topic by a huge margin.
What non-conservative electric field are you talking about?
Do you still see a lumped transformer? Or you need to bend it and bring the terminals together in a way that the wire almost encircles the core?
Yes, the complete "winding" in its entirety is a lumpable black box voltage source for everything that happens outside of the transformer.
What non-conservative electric field are you talking about?
With both sides feeling like they are debating flat earthers.
Really, this feels like discussing with a flatearther.
Please don't say that. Don't think for a moment that the feeling isn't mutual.
...
And the rest not having a clue what is really being discussed.
In short it is like this.
Lewin: KVL doesn't hold for circuits immersed in a non-conservative electric field, here is the theory to support this claim and here is the demonstration.
McDonald: Your calculations and your experiment are spot-on, Lewin, but don't say KVL doesn't hold because, although it really doesn't describe your circuit very well, I can still use KVL equations to arrive at the same results. Here is the calculations. It is a math trick used to solve various problems in electromagnetism.
Lewin: Yeah. I know many authors use that trick and even call the attention to the fact that you will not find the EMF as a voltage in the circuit, but people don't pay attention to that and try to invent all kinds of unscientific explanations to prove that there is a voltage there hidden, or somehow masked, in the circuit.
McDonald: I agree, this can be misleading sometimes.
Mehdi (intruding on adults' conversation): Hey Lewin, I think you're wrong and I have McDonald's paper to prove it. Your experiment is flawed.
Lewin: Talk to Belcher. I'm retired.
Mehdi: Belcher, please, say I'm right, say I'm right, please, please, please. I'm in desperate need of viewership and I need to convey the idea that I'm an expert electromagnetism.
Belcher: Alright, Mehdi. You're right, BUT, and that's a big BUT, only when it comes to circuits with lumped components and no varying magnetic fields inside the path of the circuit.
Mehdi Woohoo! You see audience? I'm right. Who said that? An MIT professor and the paper by McDonald. Lewin is wrong. Now subscribe, hit the like bottom, pour your sweat money into my Patreon account and buy the sponsor's shit.
People do exactly that and prove how humans failed as a species.
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
Mehdi talked about a LUMPED circuit in his first video, he applied (extended) KVL to it and said "KVL holds".So if the one circuit which Lewin and Mehdi agreed about was not even an argument, then why the tarzan did Belcher say "As ARGUED by Mehdi?"
So you're saying that Mehdi argued that KVL holds for a bunch of circuits including lumpable and unlumpable, and Belcher only agreed with the argument for Mehdi's lumpable circuit?
(but neglected to say that he disagreed with any of the rest..)
About lumped and not lumped
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
That is the root of the controversy. Everything else is noise.
Lewin thinks that this is the definition of KVL:
\$\oint_{}^{}E.dL=0\$
While this is the accepted definition of KVL (since at least 1909, the earliest reference I found, but must likely older than that):
\$emf=\oint_{}^{}E.dL=-\frac{d }{dt}\int_{S}^{}B.dS\$
And before the usual blockheads start arguing with me, read the 5 pages I took from "Engineering Electromagnetics" by Hayt and Buck (8th edition)
So, what is generating the external electric field? Is the circuit under test between the plates of a giant capacitor with a varying voltage applied to it? I thought that in Lewin's experiment we had an varying external magnetic field generated by a coil. That is why I am asking.
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
That is the root of the controversy. Everything else is noise.
Lewin thinks that this is the definition of KVL:
\$\oint_{}^{}E.dL=0\$
While this is the accepted definition of KVL (since at least 1909, the earliest reference I found, but must likely older than that):
\$emf=\oint_{}^{}E.dL=-\frac{d }{dt}\int_{S}^{}B.dS\$
And before the usual blockheads start arguing with me, read the 5 pages I took from "Engineering Electromagnetics" by Hayt and Buck (8th edition)
You call others 'blockheads' but after 13 pages in this thread, and nearly forty in the previous one you have not yet understood that Hayt is talking about the 'amended KVL' that can be applied to circuits with inductors and that is not disputed here (if not for the semantics 5 + 3 + 0 = 8 vs 5 + 3 - 8 = 0 ).
Do you really think you are the only one to have read Hayt?
Dave, KVL doesn't hold under a varying magnetic field.
You call others 'blockheads' but after 13 pages in this thread, and nearly forty in the previous one you have not yet understood that Hayt is talking about the 'amended KVL' that can be applied to circuits with inductors and that is not disputed here (if not for the semantics 5 + 3 + 0 = 8 vs 5 + 3 - 8 = 0 ).
Do you really think you are the only one to have read Hayt?
Really? So you are admitting that the very first post in this thread is incorrect? Here it is for reference:Dave, KVL doesn't hold under a varying magnetic field.
You call others 'blockheads' but after 13 pages in this thread, and nearly forty in the previous one you have not yet understood that Hayt is talking about the 'amended KVL' that can be applied to circuits with inductors and that is not disputed here (if not for the semantics 5 + 3 + 0 = 8 vs 5 + 3 - 8 = 0 ).
Do you really think you are the only one to have read Hayt?
Really? So you are admitting that the very first post in this thread is incorrect? Here it is for reference:Dave, KVL doesn't hold under a varying magnetic field.
Inside your circuit path. Or inside any loop (such as a measurement loop) you wanna apply the voltage loop rule to.
But if you can hide the flux inside an inductor and skip it, by considering your circuit path jumping at the terminals, then you end up with a circuit path that is flux free. There you can apply 'modified', 'extended', 'new', 'upgraded', 'enhanced' KVL by treating the surface integral on the rhs AS IF it were a path integral on the left. So, you go from 5 + 3 + 0 = 8 to 5 + 3 - 8 = 0 . And you can feel like you're in high school again.
But for circuits where it is not possible to 'hide' the flux inside a 'detached' component, like Lewins ring WHOSE CIRCUIT PATH IS REQUIRED TO RUN AROUND THE CHANGING FLUX - IT IS A GEOMETRIC CONSTRAINT IMPOSED BY DESIGN - you can no longer pull the 'extended KVL' trick. You have to fold back to Faraday.
Who was it again in the original KVL forum thread that deleted all their (excellent) contributions?
Who was it again in the original KVL forum thread that deleted all their (excellent) contributions?The problem is that jesuscf had read them before I deleted them. Those contribution did not do any good to him, it appears (well, back then IIRC he was arguing that Lewin's ring was a transmission line).
Also, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
That is the root of the controversy. Everything else is noise.
Lewin thinks that this is the definition of KVL:
\$\oint_{}^{}E.dL=0\$
While this is the accepted definition of KVL (since at least 1909, the earliest reference I found, but must likely older than that):
\$emf=\oint_{}^{}E.dL=-\frac{d }{dt}\int_{S}^{}B.dS\$
And before the usual blockheads start arguing with me, read ....
Also, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)
Yes, I saw it. I'll give it a shot.
Since you've formulated an ideal transformer, the easiest way to calculate the result is to lump the resistance of the wires and use "reflection" to transform all resistors and voltage sources over to the secondary side. The result is attached.
I'd like to add, though, that this has nothing to do with what we're discussing here. This "assignment" is so remote from Physics that you need to know nothing about Faraday or Maxwell, just some basic rules of circuit theory. But that's what engineers are being taught today in their first or maybe second year: how to work with equivalences so that you don't need to get into the nitty gritty of the REAL WORLD you're demanding to model in every other post.
(https://i.postimg.cc/vHF2XXjf/IMG-20211119-084936.jpg)
Thank you!
It does have to do with some of what we're talking about - it is related to the experiment with the copper loop secondary winding we did the other day.
But the point is to give you three an opportunity to demonstrate that you do know something about the topic.
Now let's see if the other two fellas come up with the same answer as you. As I said, once all three have shared their answer, I'll share mine. If they don't do so in a couple days, I'll just assume they don't know how to do it and share mine anyway.
Or maybe it's like this:
Lewin: Hello, hello, hello! Today I am going to show you something amazing! Something so amazing that you will be telling your grandchildren about it!
Lewin: In fact, it is so amazing that this is probably the only time in your entire life that you will see it!
He then presents an air core transformer, which he has incorrectly drawn on the chalkboard, and declares:
Lewin: KVL IS FOR THE BIRDS! All the textbooks are wrong! Only I am the source of truth on this matter, and even my fellow professors think I CHEATED! That shows you what THEY do!! They must be all cheaters! Yes, the whole world is insane but me!
Mehdi shocks himself a few times to see if this newfound knowledge will sink in and make sense. But it doesn't, so like any seeker of truth worth his sparks, he shocks himself a few more times and maybe melts down some clip leads, and then gets busy doing experiments, and finds that Lewin was incorrectly probing.
Mehdi: Professor Lewin, good sir, I tried my best to understand this, but I think you're not probing correctly. What am I missing?
Lewin: FLAT EARTHER! FLAT EARTHER! I do not argue with flat earthers! I won't even watch your video, but you're just wrong! KVL IS FOR THE BIRDS!
Mehdi: Professor McDonald, Professor Belcher, I'm really trying my best to understand this, and my fingers hurt and it smells like burnt clip leads in here. It looks to me like when correctly probing, KVL holds fine. It looks like Professor Lewin did not account for the dB/dt in the loop formed by his volt meter leads, which he did not depict as being magnetically coupled to his loop under test. But he won't even watch my video. What am I missing here?
McDonald: Yeah, he probably can't stand to see you shocking yourself and burning up perfectly good clip leads.
McDonald: Also, Dr. Lewin is as much of a showman as you. He uses diversion and an obsolete version of a "law" to create an apparent paradox.
McDonald: But you are right, Lewin’s circuit is within the range of applicability of Kirchhoff’s loop equations, which
can be used to predict measurements by the “voltmeters” in the experiment.
Belcher: Lewin has fallen for a very common misconception where he thinks that the -L(dI/dt) voltage read by volt meters represents -∫E.dl through the inductor, but that's false. Feynman is very clear that while -∫E.dl through a superconductor is zero, the voltage difference across the inductor is defined as ∮E.dl (which he says is EMF) -- and this is Faradays law -L(dI/dt).
Belcher: According to Feynman's definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds) +V - IR - Q/C - L(dI/dt)=0, but the first three terms here are the -∫E.dl through various circuit elements, and the last term has NOTHING to do with the -L(dI/dt) through the inductor, which is the part that Lewin is all hung up on about being zero. The -∫E.dl term is zero, but it's not the only term: The remaining term, -L(dI/dt), is not zero, and he's ignoring that.
Belcher: In that sense, you correctly argue that KVL holds. Just keep in mind that because the inductor is so different from the other elements, it is defined differently. But it's still a unit of volts, it's still a real measurable -- and lumpable voltage for the sake of KVL.
Mehdi shocks himself and burns up some more wires.
Also, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)
About lumped and not lumped
For the other forum fellows who have not yet deciphered your view: Jesse here, wants to treat the two red straight segment of wire in his setup as two distinct lumped transformers.Are you saying that the two red wires passing through the two halves of my transformer core are not lumpable voltage sources?
Well, it is kinda lumpable, and if you can attach it to a circuit that can be shrunk (lumped) to a point (this requires that there be no flux caught inside), you can consider it a lumped component in a lumped circuit.
Problem is, you cannot have a spatially extended component along your lumped circuit path, so you at least need to have the terminals close together, ideally separated by an infinitesimal distance.
In this picture I used the terms lumpable, kinda lumpable and unlumpable
([url]https://i.stack.imgur.com/HXv9x.jpg[/url])
lumpable kindalumpable unlumpable
But maybe it would be preferable to use: lumped, lumpable, and unlumpable. ( It's always after you have scanned them that you notice these things...)
In order to make that lumpable system of yours
([url]https://i.postimg.cc/gjhfcHXZ/screenshot-10.png[/url])
Pic torus with straight wire and circuit missing a coil
link [url]https://i.postimg.cc/gjhfcHXZ/screenshot-10.png[/url]
into a lumped transformer you just have to solve the problem of how to put those terminals close together. How do you plan to do it? There are two options
Option 1: You modify your component to fit the circuit
Take one on the other side to almost meet the other, or nearly join them together halfway. Now you can actually see a voltage in the space between terminals.
([url]https://i.postimg.cc/g2mfdRYx/screenshot-11.png[/url])
Pic bent wire around torus: change the component to fit the circuit
link [url]https://i.postimg.cc/g2mfdRYx/screenshot-11.png[/url]
And if you stay outside your black box and you do not run around the flux it will be always the same. Notiche how the charges have moved from the conductor's extreme to the resistor.
Option 2: You modify your circuit to fit the component
You insist in calling that piece of wire a transformer? Well, suit yourself, I will not alter it at all. But I still need to put it into the circuit, so I make connections to its end terminals
([url]https://i.postimg.cc/7LLdJkJD/screenshot-12.png[/url])
Pic change the circuit to fit the component
link [url]https://i.postimg.cc/7LLdJkJD/screenshot-12.png[/url]
and now you have your component unaltered attached to your circuit. The circuit path (highlighted here by the dotted line) is now including the component and along with it, the flux lines. And since your circuit path encompasses a variable magnetic flux, the circulation of the electric field can no longer be zero. This means that the path integral of the electric circuit depends on the path and therefore, voltage is path dependent. Kirchhoff's loop law is for the birds.
There is also the 'wishful thinking' option:
You just ignore component and circuit boundaries and cram everything together, hoping for the best. Let's apply this to your circuit inside the EI transformer.
Here on the left is the circuit with an elastic mebrane on it. It is integer and pristine. Look how happy it is, singing one of Madonna's earliest greatest hits.
But then you put it inside the EI transformer. Do you really think you can do that without breaking the membrane? Look what you did to your little circuit's membrane:
([url]https://i.postimg.cc/65LmH3dt/screenshot-13.png[/url])
fig rammed to death
link [url]https://i.postimg.cc/65LmH3dt/screenshot-13.png[/url]
I really hope you had proof of previous consent, because you broke the law: Kirchhoff's law, to be specific.
([url]https://i.postimg.cc/xd7xkbSy/screenshot-17.png[/url])
Just look at the circuit path.
link [url]https://i.postimg.cc/xd7xkbSy/screenshot-17.png[/url]
The broken membrane is proof that your circuit cut the flux lines. KVL is for the birds. Also, since your circuit path is going around the changing flux with no way to exclude it, your circuit is unlumpable. Lewin would be proud of you.
Bonus Track: What's the deal with the straight partial 'turn'?
I believe I figured you out now.
You are a lumper who believes that when a piece of wire 'goes through the hole' in the transformer, it develops a voltage, that is nonzero, irregardless of the path it is computed on! As if the hole was some kind of portal to another dimension, like a stargate.
No. If it intercepts the induced electric field, the wire gets polarized, and you might see charges of opposite sign at the extremities, but the voltage between point A at one end and point B at the other end is not unique: it depends on the path.
Along all these paths, the voltage (i.e. the work done per unit charge that is compute as minus path integral of E.dl) is zero (just like with a polarized conductor in an electrostatic field - see my previous silent post)
([url]https://i.postimg.cc/mZ7XDDpC/screenshot-14.png[/url])
Fig straight wire and paths zero v
link [url]https://i.postimg.cc/mZ7XDDpC/screenshot-14.png[/url]
Along this other type of paths, paths that together with the piece of wire form a loop that runs around the changing flux, the voltage is nonzero ( one turn emf, so to speak). There is your transformer.
([url]https://i.postimg.cc/HL70hZfX/screenshot-15.png[/url])
Fig straight wire and paths emf
link [url]https://i.postimg.cc/HL70hZfX/screenshot-15.png[/url]
But how can you make it lumped / part of a lumped circuit? Bend the conductor a little more so as to bring the terminals almost together, as shown above. Now you can insert it into a shrinkable circuit and, if the circuit path does not include variable flux you have a lumped circuit where KVL holds. You will see a jump in voltage at the component's terminals. The displaced charge is not there, though, it is at the resistor's boundaries if there is one, or facing the gap if it is open circuited.
Which side is the hole in the core?
Incidentally, this is the equivalent of what you want to consider a lumped transformer with the toroidal or EI cores, but with the core in the form of an infinitely long cylinder where the primary is an infinitely long solenoid. So, you have a piece of wire, and the 'hole' is basically the whole space. Where is left of the hole, or the right of the hole? Is the wire inside the core, or outside of it?
([url]https://i.postimg.cc/qvWyyczR/screenshot-16.png[/url])
Pic straight wire solenoid
link [url]https://i.postimg.cc/qvWyyczR/screenshot-16.png[/url]
Do you still see a lumped transformer? Or in order to call that piece of polarized wire a transformer you first need to bend it and bring the terminals together in a way that the wire almost encircles the core?
But how can you make it lumped / part of a lumped circuit? Bend the conductor a little more so as to bring the terminals almost together, as shown above. Now you can insert it into a shrinkable circuit and, if the circuit path does not include variable flux you have a lumped circuit where KVL holds. You will see a jump in voltage at the component's terminals. The displaced charge is not there, though, it is at the resistor's boundaries if there is one, or facing the gap if it is open circuited.
Also, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)Yes, I saw it. I'll give it a shot.
Yes, I saw it. I'll give it a shot.Please, don't. He's just trying to pollute the thread.
He probably pulled out an old high school problem he had solved, and now wants us to waste out time on it to prove what?
As if one could not google how to computed inductances values, or how to model a transformer with lumped parameters? I did t
Besides having nothing to do with the unlumpable Lewin's ring, his problem is not even interesting because he doesn't even model the hysterisis. And with all the simplification assumptions one has to make to get to a lumped model, he wants what? Ten significative digits?
Please, move the problem in the beginner section of the forum, if you want to solve it. Here it will only dilute the thread.
About lumped and not lumpedAre you saying that the two red wires passing through the two halves of my transformer core are not lumpable voltage sources?
For the other forum fellows who have not yet deciphered your view: Jesse here, wants to treat the two red straight segment of wire in his setup as two distinct lumped transformers.
Do I understand correctly that the voltage across the resistor (and consequently the heat produced by the resistor) will change when I go from Option 1 configuration and Option 2 configuration?
Because it will uselessly waste space here.Yes, I saw it. I'll give it a shot.Please, don't. He's just trying to pollute the thread.
Please, move the problem in the beginner section of the forum, if you want to solve it. Here it will only dilute the thread.
Why? Problem and solution nicely demonstrate his level of expertise. That can't hurt.
Besides, the solution (trivial, 3-resistor circuit plus voltage source)
You need to model more than that.Nah, not really. Look at the constraints given (ideal core, infinite permeability, perfect coupling) and imagine what that does to the standard "non-ideal transformer" model. So much for "dealing with the real world".
Or maybe it's like this:
Lewin: Hello, hello, hello! Today I am going to show you something amazing! Something so amazing that you will be telling your grandchildren about it!
Lewin: In fact, it is so amazing that this is probably the only time in your entire life that you will see it!
He then presents an air core transformer, which he has incorrectly drawn on the chalkboard, and declares:
Lewin: KVL IS FOR THE BIRDS! All the textbooks are wrong! Only I am the source of truth on this matter, and even my fellow professors think I CHEATED! That shows you what THEY do!! They must be all cheaters! Yes, the whole world is insane but me!
Mehdi shocks himself a few times to see if this newfound knowledge will sink in and make sense. But it doesn't, so like any seeker of truth worth his sparks, he shocks himself a few more times and maybe melts down some clip leads, and then gets busy doing experiments, and finds that Lewin was incorrectly probing.
Mehdi: Professor Lewin, good sir, I tried my best to understand this, but I think you're not probing correctly. What am I missing?
Lewin: FLAT EARTHER! FLAT EARTHER! I do not argue with flat earthers! I won't even watch your video, but you're just wrong! KVL IS FOR THE BIRDS!
Mehdi: Professor McDonald, Professor Belcher, I'm really trying my best to understand this, and my fingers hurt and it smells like burnt clip leads in here. It looks to me like when correctly probing, KVL holds fine. It looks like Professor Lewin did not account for the dB/dt in the loop formed by his volt meter leads, which he did not depict as being magnetically coupled to his loop under test. But he won't even watch my video. What am I missing here?
McDonald: Yeah, he probably can't stand to see you shocking yourself and burning up perfectly good clip leads.
McDonald: Also, Dr. Lewin is as much of a showman as you. He uses diversion and an obsolete version of a "law" to create an apparent paradox.
McDonald: But you are right, Lewin’s circuit is within the range of applicability of Kirchhoff’s loop equations, which
can be used to predict measurements by the “voltmeters” in the experiment.
Belcher: Lewin has fallen for a very common misconception where he thinks that the -L(dI/dt) voltage read by volt meters represents -∫E.dl through the inductor, but that's false. Feynman is very clear that while -∫E.dl through a superconductor is zero, the voltage difference across the inductor is defined as ∮E.dl (which he says is EMF) -- and this is Faradays law -L(dI/dt).
Belcher: According to Feynman's definition, the sum of all the voltage differences around the circuit is zero (that is, KVL holds) +V - IR - Q/C - L(dI/dt)=0, but the first three terms here are the -∫E.dl through various circuit elements, and the last term has NOTHING to do with the -L(dI/dt) through the inductor, which is the part that Lewin is all hung up on about being zero. The -∫E.dl term is zero, but it's not the only term: The remaining term, -L(dI/dt), is not zero, and he's ignoring that.
Belcher: In that sense, you correctly argue that KVL holds. Just keep in mind that because the inductor is so different from the other elements, it is defined differently. But it's still a unit of volts, it's still a real measurable -- and lumpable voltage for the sake of KVL.
Mehdi shocks himself and burns up some more wires.
I’d say you’d make an excellent Hollywood script writer, if we didn’t know who invented all the myth above for the sole aim of boosting his own viewership, at the expense of truth. But we’re not buying it because serious science and engineering.
As you keep forwarding this misinformation, you’ll not advance a single bit in the understanding of the electromagnetic phenomenon, exactly as Mehdi declares every time, including in this very interview.QuoteAlso, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)
Your question is not aimed at honestly trying to understand the issue. If it were, you would have already heeded what we’ve written all along this thread.
Because it will uselessly waste space here.Yes, I saw it. I'll give it a shot.Please, don't. He's just trying to pollute the thread.
Please, move the problem in the beginner section of the forum, if you want to solve it. Here it will only dilute the thread.
Why? Problem and solution nicely demonstrate his level of expertise. That can't hurt.QuoteBesides, the solution (trivial, 3-resistor circuit plus voltage source)
You need to model more than that. If you find it, have a look at K. C. A. Smith & R. E. Alley "Electrical Circuits, an introduction", chapter 4, section 9 "Single-phase power transformers". It has the simplest treatment of 'real' transformers I have ever seen.
He will drag you down in a series of dozens of post, arguing about any simplificative assumption he did not make in his high-school exercise, and defending any simplification he made, no matter how unrealistic that may be (like--- this looks like a welder's transformer and he's not considering saturation?). It will go on forever.
Remember, I have a crystal ball that almost never fails me.
Edit: grammar! and a little addition.
Also, Hey, did you see my request to you here? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3820280/#msg3820280)
Yes, I saw it. I'll give it a shot.
Since you've formulated an ideal transformer, the easiest way to calculate the result is to lump the resistance of the wires and use "reflection" to transform all resistors and voltage sources over to the secondary side. The result is attached.
I'd like to add, though, that this has nothing to do with what we're discussing here. This "assignment" is so remote from Physics that you need to know nothing about Faraday or Maxwell, just some basic rules of circuit theory. But that's what engineers are being taught today in their first or maybe second year: how to work with equivalences so that you don't need to get into the nitty gritty of the REAL WORLD you're demanding to model in every other post.
He will drag you down in a series of dozens of post, arguing about any simplificative assumption he did not make in his high-school exercise, and defending any simplification he made, no matter how unrealistic that may be (like--- this looks like a welder's transformer and he's not considering saturation?). It will go on forever.
Remember, I have a crystal ball that almost never fails me.
He will drag you down in a series of dozens of post, arguing about any simplificative assumption he did not make in his high-school exercise, and defending any simplification he made, no matter how unrealistic that may beThe fact is I very clearly stated that the core had infinite permeability and was ideal, that the coupling was perfect and ideal, and that the AC generator was ideal, and that the resistor was ideal.
Anyway, my turn now:
See the attached arrangement. If it looks familiar, this is your EI-core setup, just with a toroidal core instead.
What voltages would you measure across the resistors? What voltages would you measure across the wires? Show the arrangement of your probe wires.
The actual value of R is not relevant, assume it is large enough to make the resistance of the wiring negligible. Assume the magnetic flux in the core corresponds to a value of "1V" induced in the secondary.
Also assume the length of the wires between the resistors is identical, so that it looks nice and symmetric (hint: it doesn't actually matter, I'm just a sucker for symmetric arrangements).
(https://i.postimg.cc/CMm4MXwV/IMG-20211119-112430.jpg)
About lumped and not lumpedAre you saying that the two red wires passing through the two halves of my transformer core are not lumpable voltage sources?
For the other forum fellows who have not yet deciphered your view: Jesse here, wants to treat the two red straight segment of wire in his setup as two distinct lumped transformers.
I see you are capable of quoting and entire post. Good. How about (re-)reading it, now? Because to answer this question I should rewrite it as it is.QuoteDo I understand correctly that the voltage across the resistor (and consequently the heat produced by the resistor) will change when I go from Option 1 configuration and Option 2 configuration?
Of course you don't understand correctly.
Here is the sentence you highlighted. I will toss in the next sentence too because it's black friday month.
"You will see a jump in voltage at the component's terminals. The displaced charge is not there, though, it is at the resistor's boundaries if there is one, or facing the gap if it is open circuited."
Now, what makes you think that the component is the resistor? Especially when the sentence immediately after says "The displaced charge is not there, though, it is at the resistor's boundaries if there is one, or facing the gap if it is open circuited."
If "NOT THERE" means "AT THE RESISTOR'S", how can "there" mean "at the resistor's"?
Obviously, the 2R is not just a resistor, it also serves as a secondary winding -- albeit a secondary winding with a high resistance -- like the 100V:10V transformer problem you solved for, except the primary winding has more resistance than the load resistor.
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
Sigh...
YES. V1 and V2 will be the same.
Obviously, the 2R is not just a resistor, it also serves as a secondary winding -- albeit a secondary winding with a high resistance -- like the 100V:10V transformer problem you solved for, except the primary winding has more resistance than the load resistor.
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
I'm sorry, I understand I may need to clarify "R" and "2R". I hoped you'd understand that "2R" means that this resistor has a value that is "two times R". In other words, the second ("inner" if you will) resistor has double the resistance of the first ("outer") resistor. Would you correct your analysis?
(https://i.postimg.cc/fTgyDNp0/20211119-030105.jpg)Sigh...So the V1 configuration and the V2 configuration are functionally identical, and yet V2 is lumpable and V1 is not?
YES. V1 and V2 will be the same.
Do I understand correctly that if I had a loop formed by resistors and either V1 or V2, that I could use the V2 secondary and KVL holds, but if instead I used the V1 configuration, then KVL fails?
(https://i.postimg.cc/fTgyDNp0/20211119-030105.jpg)Sigh...So the V1 configuration and the V2 configuration are functionally identical, and yet V2 is lumpable and V1 is not?
YES. V1 and V2 will be the same.
Do I understand correctly that if I had a loop formed by resistors and either V1 or V2, that I could use the V2 secondary and KVL holds, but if instead I used the V1 configuration, then KVL fails?
You might have noticed that in my posts I sometimes write "circuit path" and "in the circuit" in bold, or in italics.
So, let's try this.
Pick a colored pen or pencil and draw a finely dotted line following the circuit path for both circuits, following the examples I gave in my "About Lumped and non Lumped" post. Then select two points A and B at random on both circuits - in the same position for both.
Post it, and then I will show you when and where the voltage can be non unique and KVL dies.
Edit: plurals!
So, what is generating the external electric field? Is the circuit under test between the plates of a giant capacitor with a varying voltage applied to it? I thought that in Lewin's experiment we had an varying external magnetic field generated by a coil. That is why I am asking.
There is a long core with a varying magnetic flux at the center of the ring. The magnetic field is only varying within the core. I had pointed out that the return flux of the solenoid would generate a varying magnetic field as well, but apparently that has been shown both mathematically and experimentally to be very low. I haven't seen or measured the apparatus myself, so I'll assume that is correct--even if there were such a contribution, it would be a lot lower than the contribution directly from the core. So the circuit itself is not 'immersed' in a varying magnetic field of any significance.
This varying flux creates a rotational electric field concentrically around it. This rotational field is said to have 'curl', and that makes it non-conservative, which essentially means that you can lose or gain energy when you go in a circle and come back to the same spot. In a field with no curl, coming back to the same spot will always result in no net work--that is conservative.
Given your previous comments I would have assumed you already knew all that, so that's why I'm wondering why you are asking. Have I misunderstood?
never mind.
here's the picture.
(https://i.postimg.cc/15n8XGXJ/Voltage-can-be-path-dependent.jpg)
https://i.postimg.cc/15n8XGXJ/Voltage-can-be-path-dependent.jpg
(I cannot see the pics from postimg from this system, so I don't know if you posted yours yet. Incidentally this is the reason I post the links under every picture - so that I can know there is one)
Ok. You did not post any image, but it's fine. Now, the colored paths are the paths along which you compute the voltage. Voltage is a path integral: you move on a path, consider a small displacement dl and compute the scalar product of E.dl - keep summing up for all infinitesimal intervals the path has been partioned into and then add a minus sign to get the voltage.
This IS the voltage a voltmeter with infinite impedance and zero resistivity probes will measure if the probes followed one of those colored paths and the voltmeter was somewhere along it (ideally without occupying any space).
(I tossed in a few 'external paths, for free)
If the dB/dt zone is OUTSIDE your circuit's premises, voltages along any path between two points A and B will be the same.
If the dB/dt zone in INSIDE your circuit's premises, the paths that cut through it or go 'on the other side' will see different contributes from the flux than those that do not cut it and are on the 'good side'.
Do I have to explain why, if the voltage along two different paths joining the same points A and B are different, then KVL dies?
My challenge of the 100v:10v stepdown transformer was aimed at helping me understand who here knows what they are talking about.
I can see the images just fine from other systems. I use postimg. But I cannot see them from THIS system.
You seem to lack the capacity to discern between levels of gray. It's either all white or all black.
It feels like being in that 70s movie, "The day of the dolphin".
Yes, I was talking about the toroid because that is the way we chose to steer the flux. In the case matter is in the way we can still compute voltage as path integral, by knowing the field. Don't like the toroid in the way? Make a gap. Slide your circuit in there through the gap (remember the elastic membrane? It will be rammed by the flux just like before (yes, yes, there will be fringing, I don't care, what counts it's the flux inside the circuit). Don't like the gap? Use a magnet and shoot it through your circuit - there will be flux lines and we are there.
Now, let me guess, the next objection will be "but if I shoot a magnet through the circuit, how can I be so fast to read the voltmeter?"
So, use a solenoid.
You built a pancake solenoid to put under your Lewin ring, right? You put the hands of the clock in a way that you can access the space where the magnetic field change, right? I would tell you to do the experiment with that, but your system has so much flux leakage that you can only try the orange paths. In fact, your clock hands are examples of orange paths, with the voltmeter at the center.
What is the next objection? That you cannot put a voltmeter inside a circuit branch with a resistor because you cannot drill a hole along the conductor and the resistor and there are no microscopic voltmeters to fit such a tight space?
Do you really think that measurement instruments only works by implementing verbatim the definition of the variable they measure?
Do amperometers count the single electrons and use a tiny stopwatch to measure the current?
Do they necessarily have to sit inside the branch they measure current? Ever seen a current clamp? Never heard of Hall effect?
It is fascinating to see the amount of irrational objection you need to throw to persist in your religious blindness.
-
Anyway, take one green path, and one purple path, where you can place your voltmeter even if there is a torus. Along one you read 5V and along the other your read 0V. KVL dies there. Wanna see in the circuit: the branch with the resistor is a green path, the branch with the conductor alone is the purple path. One gives 5V and one gives 0V - and you can show that it has to be that way because if you compute the fields, these values are what you get by computing the path integrals.
Everything checks.
And what is the sum of voltages if you circle the ring? 5V + 0V = 5V, or circulation of E along the ring = EMF.
KVL says: circulation of E along the ring = 0
Faradays says: circulation of E along the ring = EMF
I wonder who is right.
It is fascinating to see the amount of irrational objection you need to throw to persist in your religious blindness.
Do you really think that measurement instruments only works by implementing verbatim the definition of the variable they measure?
Do amperometers count the single electrons and use a tiny stopwatch to measure the current?
Do they necessarily have to sit inside the branch they measure current? Ever seen a current clamp? Never heard of Hall effect?
Anyway, take one green path, and one purple path, where you can place your voltmeter even if there is a torus. Along one you read 5V and along the other your read 0V. KVL dies there. Wanna see in the circuit: the branch with the resistor is a green path, the branch with the conductor alone is the purple path. One gives 5V and one gives 0V - and you can show that it has to be that way because if you compute the fields, these values are what you get by computing the path integrals.
Everything checks.
And what is the sum of voltages if you circle the ring? 5V + 0V = 5V, or circulation of E along the ring = EMF.
KVL says: circulation of E along the ring = 0
Faradays says: circulation of E along the ring = EMF
You really seem to have a religious aversion to admitting that KVL *WOULD* give every appearance of holding for both my V1 and V2 configurations as measured with a volt meter.
KVL says: circulation of E along the ring = 0
Faradays says: circulation of E along the ring = EMF
Suuure! Because when Kirchhoff postulated his 'voltage law', he didn't have a emf in the circuit. Are you even aware that there more more than one way of generating an emf and using it in a circuit?
My challenge of the 100v:10v stepdown transformer was aimed at helping me understand who here knows what they are talking about.
OK. So you want an answer to your question? Here it is: stop trying to understand who here knows what they are talking about. There's no guru in science. Mehdi said that he wished Feynman was alive to answer his questions about electromagnetism. Turns out we don't need Feynman. We have nature. Nature told Feynman what he knew and it is apt to answer whatever questions we may have.
You KVLers are obsessed with ascertaining who is wrong and who is right. Forget about that.
Who says KVL doesn't always hold is nature, not Lewin.
There can be no electric fields inside a static conductor, except the one to sustain a voltage as a function of its current as per Ohm's law. This is one of the first things we learn in whatever electromagnetism course out there.
The conclusions of your experiment are wrong because you don't listen to what the phenomenon right in front of you is telling. The only thing you listen to is "Lewin is wrong so I must be right". You ain't gonna get anywhere that way.
There can be no electric fields inside a static conductor, except the one to sustain a voltage as a function of its current as per Ohm's law.
There can be no electric fields inside a static conductor, except the one to sustain a voltage as a function of its current as per Ohm's law.
OK. So you want an answer to your question? Here it is: stop trying to understand who here knows what they are talking about.I'm figuring it out. thinkfat knows more than you or snedri about transformers. He solved the puzzle, and did it right sharp too.
There's no guru in science.I'll allow you to be the prime authority on that regarding only yourself. But I agree, you're not him if there is one :-DD
You KVLers are obsessed with ascertaining who is wrong and who is right. Forget about that.I'm just looking for the truth. People tell me my transformer secondaries won't hold up as a lumped element in a loop for KVL. But when I test with real volt meters, they seem to show that KVL holds.
Who says KVL doesn't always hold is nature
The conclusions of your experiment are wrong because you don't listen to what the phenomenon right in front of you is telling.
KVL says: circulation of E along the ring = 0
Faradays says: circulation of E along the ring = EMF
Suuure! Because when Kirchhoff postulated his 'voltage law', he didn't have a emf in the circuit. Are you even aware that there more more than one way of generating an emf and using it in a circuit?
Kirchhoff experimented with lumped sources of EMF. Batteries, that are localized in the circuit. In his statement he used the words "auf dem Wege", which means along the way, on the path. Can you locate it on the path, anywhere?
The EMF due to a changing magnetic field is essentially a relativistic effect, and it does not appear anywhere in the circuit. And it is also the manifestation of an actual electric field, the electric field that causes charges to move. It is not just something that happens to have dimensions of a voltage, it is actually a 'component' of the quantity voltage. That electric field, the induced electric field Eind becomes a component of the total electric field, together with the conservative field of the displaced charge.
And since electron only experience the total electric field, there is no way for them to know which portion came from the displaced charges and which came from the changing magnetic field.
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
The EMF from a changing magnetic field is the only one to appear on the rhs - it's a direct consequence of Faraday's law, one of Maxwell's equations that expresses a fundamental property of the electromagnetic field.
You really seem to have a religious aversion to admitting that KVL *WOULD* give every appearance of holding for both my V1 and V2 configurations as measured with a volt meter.
Inner peace.
Inner peace.
Inner peace.
Ok, let's see...
Is FIVE equal to ZERO?
Because if five equals zero, then KVL holds in the nonlumped circuit.
If five is not equal to zero, then KVL does not hold in the nonlumped circuit.
I say that five is not equale to zero, and therefore KVL does not hold in the nonlumped circuit.
So, question - and only this question I would like you to answer:
Is FIVE equal to ZERO?
Dude, I have supplied plenty of diagrams, if you don't understand them it's not my fault.
Put one of your voltmeters along a green path and the other along a purple path.
For the rest, try to realize that Faraday's law is one of Maxwell's equation and as such the EMF due to a changing magnetic field is not like other forms of emf.
rot E = -dB/dt
becomes (in stationary conditions - meaning we don't move things around)
circulation of E = - d/dt flux of B
Can you compute the circulation of a vector field if I give you the configuration?
Dude, I have supplied plenty of diagrams, if you don't understand them it's not my fault.
@Sredni
It's no use to throw stuff at Jesse that belongs to your world. He will either ignore it or twist it around until it fits. You will need to find something in his world that can unambiguously be shown to conflict with the reality, which is for him with a volt meter or a scope.
But it might be that he's just too far gone to be saved.
But it might be that he's just too far gone to be saved.
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
@Sredni
It's no use to throw stuff at Jesse that belongs to your world. He will either ignore it or twist it around until it fits. You will need to find something in his world that can unambiguously be shown to conflict with the reality, which is for him with a volt meter or a scope.
But it might be that he's just too far gone to be saved.
So which is it? Nature? Or the gurus that write the books and teach the courses?
Why are you bringing up static fields when we're talking about AC transformers?
But don't feel bad if I am skeptical of your opinion about whether my experiment is wrong
KVL at the very least appears to hold, then we can talk about why it's not actually holding by some specific definition.
But it might be that he's just too far gone to be saved.
Let me elaborate, based on his arrangement:
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
Jesse believes, and all his measurements confirm it, that:
Voltage is induced locally only where "stuff" is "crossing" the magnetic flux, e.g. in a transformer, only the part of the windings that are "inside" the core contribute to the voltage. Hence only the "2R" resistor acts as a "secondary"
That explains how he gets 0V across the wires and 1/3V across "R". Those are not "inside" the core and so they are no voltage sources.
And since the "2R" resistor for him is a local voltage source, he subtracts the 1V induced EMF from its "ohmic" voltage drop (due to the 1/3R current) and arrives at -1/3V.
The probe wires for the rightmost volt meter are arranged so that, in his world, they don't form a "secondary" because, well, they're not "inside" the core. For him that's the only correct way.
Would I suggest a different path for the probe wires, one that doesn't form a loop around the core, he would reject it because then the wires would necessarily "cross" the inside of the core and form a "secondary" that would compensate the voltage generated in "2R", skewing the measurement.
And guess what: the measurements are "correct" even in my world. Presented with above setup, I will come to the same prediction. Of course I would arrive there without ignoring/violating Maxwell-Faraday, but these mean nothing to Jesse (he believes in a completely distorted version of it).
So for him it all adds up nicely and even makes KVL work. And that's why I likened him to a flatearther: He has made up a framework for himself that is complete and can be proven by observation. Of course Belcher and McDonald would cringe at the sight and Lewin would laugh his arse off.
He also describes Mehdi's series of experiments as "very nice."
I am grateful to Mr. Sadaghdar for a number of discussions about Faraday’s Law and KVL, which have improved my
understanding of both.
So, to save Jesse (and the cause), the only way is to disprove experimentally something that must hold in his framework. That's how science has worked forever: find the "purple cow" that must not exist.Yes! Thank you! I do want the truth, but I need to see it with my own eyes, otherwise it's just me believing popular opinion, like all yall.
Bombarding him with "truth" like a Missionary will not work.
So which is it? Nature? Or the gurus that write the books and teach the courses?
Nature.
In an engineering degree we test the theories in the lab systematically. One by one. We don't treat the laws of physics as a precept given by some scientific "authority". There's no authority in science, except that of nature.QuoteWhy are you bringing up static fields when we're talking about AC transformers?
You don't even know how to ask the right questions and you think you already know more than Lewin.
I said static wire. Not static field. Static in relation to a frame of reference.QuoteBut don't feel bad if I am skeptical of your opinion about whether my experiment is wrong
It's not my opinion. You'll find it eventually. But it's a good thing that you are skeptical.
There can be no electric fields inside a static conductor, except the one to sustain a voltage as a function of its current as per Ohm's law. This is one of the first things we learn in whatever electromagnetism course out there.
Jesse believes, and all his measurements confirm it, that:
Voltage is induced locally only where "stuff" is "crossing" the magnetic flux, e.g. in a transformer, only the part of the windings that are "inside" the core contribute to the voltage. Hence only the "2R" resistor acts as a "secondary"
"However Maxwell and Faraday describe the inner workings is irrelevant to the fact that in the real world a close-magnetic-circuit-cored transformer models as if the entire voltage induced happens at the point that the winding passes through the core."
Alright, the jury is in! bsfeechannel and Sredni couldn't solve it. .
...But don't feel bad if I am skeptical of your opinion about whether my experiment is wrong -- you couldn't even solve a loaded transformer voltage question that I eventually solved.
...He couldn't solve the 10:1 loaded transformer question, like you expertly did.
...that doesn't change the fact that you couldn't solve the transformer quiz
...so if someone solved it better than me I know they are better than me, and if they can't solve it then I know they are no better than me
You can throw all the math at me you want but that's not going to prove that KVL actually fails.
For exceptionally small versions of five and exceptionally large versions of zero, possibly
Would it be fair then to say that in the real world, where wires and ferrite/iron cannot exist in the same physical space, that we don't have to worry about our volt meter leads accidentally ending up half way through the cross section of a toroid, and thus in the real world, KVL holds fine
"In the mean time, we go on to spread the truth that KVL holds when you correctly probe for loops who's size is much smaller than the wavelength of the frequency involved.
More and more people are making videos on the topic, demonstrating Lewin's error and some of them already know way more math than you and me, and the ones that don't know the math aren't going to be helped by your mathematical definition games.
They are going to be influenced by the low-level information about guys like Mehdi and all the other guys taking the practical approach -- because most people identify much more strongly with the practical approach, and won't be helped by you quoting math [...]"
"I made a video about this a few years ago and I can assure you that you will be told by viewers that you're wrong (even though you aren't). I'm glad you made the video though. The more of us that cover this topic, the more people we'll be able to reach and educate. "
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
You are so wrong on this one that you are even disagreeing with Lewin and everyone else for that matter!
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
You are so wrong on this one that you are even disagreeing with Lewin and everyone else for that matter!
Very well. Since Jesse won't do this experiment, let's see if you are willing to do it (I did it).
Are you a toroidal power transformer owner?
You know one those five inches or so big donuts?
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
You are so wrong on this one that you are even disagreeing with Lewin and everyone else for that matter!
Very well. Since Jesse won't do this experiment, let's see if you are willing to do it (I did it).
Are you a toroidal power transformer owner?
You know one those five inches or so big donuts?
Diversion and more diversions. I have a much better idea. Here, solve this very simple problem. Please post your complete solution. I'll give you a day from now, before I post the solution myself. This problem should look extremely familiar to anybody reading this forum!
A circular wire ring with a radius of 0.2 m has two resistors attached as shown in the figure. R1 has a resistance 100Ω and R2 has a resistance of 900Ω. The resistance of the wire can be ignored. The time varying magnetic flux density as shown in the figure is given by:
\$
B(t) = 0.7958 \cdot e^{\frac{{ - t}}{{0.1s}}} _{} T
\$
At t=0, determine the voltages across the resistors V1 and V2 (with the polarity as indicated in the figure) and the voltage between nodes A and D (VAD) which are half a circle apart.
voltage between nodes A and D (VAD) which are half a circle apart.[/b]
voltage between nodes A and D (VAD) which are half a circle apart.[/b]
As I've stated, the definition of that voltage is the very issue that is not agreed upon. So if you want a number for an answer, you have to specify your definition or method of measurement. One definition that might be interesting is the voltage measured by a voltmeter whose leads go in an exact straight line between the points. You would need a gap or hole in the inductor and core that are providing the magnetic flux, but that may be doable.
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
You are so wrong on this one that you are even disagreeing with Lewin and everyone else for that matter!
Very well. Since Jesse won't do this experiment, let's see if you are willing to do it (I did it).
Are you a toroidal power transformer owner?
You know one those five inches or so big donuts?
Diversion and more diversions. I have a much better idea. Here, solve this very simple problem. Please post your complete solution. I'll give you a day from now, before I post the solution myself. This problem should look extremely familiar to anybody reading this forum!
A circular wire ring with a radius of 0.2 m has two resistors attached as shown in the figure. R1 has a resistance 100Ω and R2 has a resistance of 900Ω. The resistance of the wire can be ignored. The time varying magnetic flux density as shown in the figure is given by:
\$
B(t) = 0.7958 \cdot e^{\frac{{ - t}}{{0.1s}}} _{} T
\$
At t=0, determine the voltages across the resistors V1 and V2 (with the polarity as indicated in the figure) and the voltage between nodes A and D (VAD) which are half a circle apart.
Well, if the field permeates the whole ring the flux is the product of the area of the ring times B which is spatially constant on the whole surface.
Differentiate with respect to t, change sign and you get the EMF. You need to pay attention to signs - what matters is how the flux changes.
Once you know the EMF and its verse (cw or ccwI, you know the current I(t) = EMF(t) / (R1 + R2) with the same verse established for the EMF. It will be exponentially decaying, since the time derivative of a decaying exponential is also a decaying exponential. Then you compute the voltages along the resistor branches by using R * I(t). The sign comes from that of the current and the convention of the sinks.
Fill in the values, if you want. That's a servant job.
Whatever voltage is in the ratio 9:1, like the resistors, and since the current goes down in one branch and up in the other the will appear to have opposite sign.
Happy, now?
Now, do you have a toroidal transformer? Yes or no?
(edit: grammar. It happens when you solve a problem in 40 seconds)
Or one could use the definition of voltage given by the International Electrotechnical Committe IEC 60050
https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=121-11-27 (https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=121-11-27)
and specify the path, as I did.
I don't have a toroidal transformer.
Can you solve for the value of the voltages in volts?
Also, why are you using KVL (EMF(t)-I(t)R1-I(t)R2=0) to get the solution? Are you one of the 'birds' now?
I don't have a toroidal transformer.
How unfortunate.QuoteCan you solve for the value of the voltages in volts?
Of course I can. It's not that difficult differentiate an exponential.
But I am not going to waste my time doing menial task. I gave you the full procedure to compute the solution for any type of (spatially uniform and ortogonal to the disk) B(t) and for any t.
Wanna play data entry employee? Suit yourself.
And, besides, not doing it will give you the same satisfying sensation Jesse experienced. I cannot differentiate A e^k t!!! You must be right on everything, then.QuoteAlso, why are you using KVL (EMF(t)-I(t)R1-I(t)R2=0) to get the solution? Are you one of the 'birds' now?
I am not using KVL. It is Faraday:
-path integral of E.dl is R1 I(t) + R2 I (t) (these you can locate on the ring)
-d/dt flux of B is the EMF (this you can't, and if you had a toroidal transformer you could witness it with your eyes)
Faraday says, then
-path integral of E.dl == -d/dt flux of
which is
R1 I(t) + R2 I (t) == EMF
Faraday! Exactly because around the loop you will find only what's in the lhs.
Fill in the values, if you want. That's a servant job.
I had written this post hours ago, before reading Jesse's last rant, and delayed till I had the links and the images, but I did not have to change anything except for a few addition to confirm my deductions.Dude, stop misquoting me or trying to stuff words into my mouth.Jesse believes, and all his measurements confirm it, that:
Voltage is induced locally only where "stuff" is "crossing" the magnetic flux, e.g. in a transformer, only the part of the windings that are "inside" the core contribute to the voltage. Hence only the "2R" resistor acts as a "secondary"
Yes, Jesse is a 'lumper'.
He believes that the core is some sort of magical portal, like a stargate, and when you cross it, when you 'cut through it' with your wires, they magically acquire a voltage, that is there independent of anything else.
But in the case of the infinitely long solenoid, where he cannot find the entrance of the stargate, he is forced to become a 'distributer', because the 'hole' is now the whole space and the magical source of voltage can now be inside the whole length of the conductors and even of the probes. "The probes become the secondary".
Edit: read another subsequent message before posting this and he appears to confirm that he jumps between positions depending on what suits him best at the momentQuote from: Jesse Gordon"However Maxwell and Faraday describe the inner workings is irrelevant to the fact that in the real world a close-magnetic-circuit-cored transformer models as if the entire voltage induced happens at the point that the winding passes through the core."
I have a couple of setups he should try to test his belief with his trusty voltmeter.
But the reason I keep answering him is not to convince him - ironically he is more of a flatearther of the flatearthers he mocks on his channel - but (among other things) to observe the rejection mechanisms when he is cornered.
First he needed to reassure himself with that exercise on the transformer and you can see the false equivalence (reiterated in several messages, including the last one)You act like there's something wrong with doing experiments. Maybe if you did some you wouldn't be so wrong.
Quote from: Jesse GordonAlright, the jury is in! bsfeechannel and Sredni couldn't solve it. .
...But don't feel bad if I am skeptical of your opinion about whether my experiment is wrong -- you couldn't even solve a loaded transformer voltage question that I eventually solved.
...He couldn't solve the 10:1 loaded transformer question, like you expertly did.
...that doesn't change the fact that you couldn't solve the transformer quiz
...so if someone solved it better than me I know they are better than me, and if they can't solve it then I know they are no better than me
"See, you did not do my high school exercise, therefore you cannot do it and since I can, the only possible conclusion it that I know all of EM better than you. Even if I have no idea how to compute the circulation of a vector field".
Then he is trying to reject all analytical reasoning because he cannot handle the math.
Quote from: Jesse GordonYou can throw all the math at me you want but that's not going to prove that KVL actually fails.
to the point that when asked if 5 = 0 his answer is:Quote from: Jesse GordonFor exceptionally small versions of five and exceptionally large versions of zero, possibly
For exceptionally small versions of five and exceptionally large versions of zero, possibly :-DD :-DD :-DD :-DD :-DD
So, now all proofs he accepts are those that he himself can do with his limited equipment: a pancake solenoid that has a ton of stray field on the outside (it's basically a multifilar coil), and an EI transformer that will have 'returning legs' on both sides of the ring and nearly no space inside the legs. He also once produced a tiny toroidal core in whose hole he could not fit the probes.Why do you blather on?
And he rejects experiments that could prove him wrong, like building a long solenoid to confine the field and go all around it or even right above it, or using a transformer with a gap big enough to fit the probes...
If you cannot prove he's wrong using the limited setup he has, then he must be right.Stop the BS dude. You're grabbing at straws.
Quote from: Jesse GordonWould it be fair then to say that in the real world, where wires and ferrite/iron cannot exist in the same physical space, that we don't have to worry about our volt meter leads accidentally ending up half way through the cross section of a toroid, and thus in the real world, KVL holds fine
(Even tho he seems to have changed language: now KVL 'have the appearance of holding' and from one of the latest posts: 'I never said that's actually how Faraday or Maxwell describe it, or even that is how it is working'). So, at least he appears to be right.
But the most interesting thing I have got from him is his lucid analysis of what in the older thread on this topic I called 'scientific populism'.Quote from: Jesse Gordon"In the mean time, we go on to spread the truth that KVL holds when you correctly probe for loops who's size is much smaller than the wavelength of the frequency involved.
More and more people are making videos on the topic, demonstrating Lewin's error and some of them already know way more math than you and me, and the ones that don't know the math aren't going to be helped by your mathematical definition games.
They are going to be influenced by the low-level information about guys like Mehdi and all the other guys taking the practical approach -- because most people identify much more strongly with the practical approach, and won't be helped by you quoting math [...]"
He is 100% right.
This is how politics has always worked: you don't need to tell the truth or correctly solve problems, far from it, you just need to tell your electorate what they want to hear. Make them feel smart, even if they are dumb as rocks, by using their language and indulging their wrong beliefs. They will adore you and they will give you their vote and their money.
You will never find the emf along the circuit path, like the lumped EMF Kirchhoff experimented with.
You are so wrong on this one that you are even disagreeing with Lewin and everyone else for that matter!
Very well. Since Jesse won't do this experiment, let's see if you are willing to do it (I did it).
Are you a toroidal power transformer owner?
You know one those five inches or so big donuts?
in case you didn't realize it, Faraday's law is one of the many forms you can encounter KVL.
For example, using your same flawed logic, we can argue that a thermocouple circuit is not solved using KVL but the Seebeck effect. Imagine if we would have to 'name' the solution of every possible circuit based on the nature of its EMF...
Why induction EMF is special...in case you didn't realize it, Faraday's law is one of the many forms you can encounter KVL.
No. Faraday's law is a fundamental law of nature, that expresses a fundamental property of the electromagnetic field. It tells you that a changing magnetic field is associated with a curling electric field. There is a reason it is one of four Maxwell's equations, the pillars of ALL classical electrodynamics.
...and why you cannot locate it in the closed circuitQuoteFor example, using your same flawed logic, we can argue that a thermocouple circuit is not solved using KVL but the Seebeck effect. Imagine if we would have to 'name' the solution of every possible circuit based on the nature of its EMF...
You've got it all backwards.
The other sources of EMF lie along the path ("auf dem Wege", remember?), and as such are taken care of by the circulation of E.dl - which is the path integral extended to the whole circuit - that is on the left-hand side. The only form of EMF that falls into the right-hand side is - you guessed it - electromagnetic induction. It's a special one because it is a manifestation of a property of the electromagnetic field and it has its own Maxwell equation, and this is not the first time I wrote that in this thread.
- When the magnetic components can be lumped, we can make - with a mathematical trick (take the term from the right side and move it to the left side by changing the sign) - them appear in the form of path integral as a piece of the circulation of E (I have explained how to do that, as well). You know, when instead of following the filament you consider the jump at the terminals (as explained by Hayt, which you quote but seem not to understand)?
- But when the magnetic 'component' cannot be lumped - i.e. it is unlumpable as the Romer-Lewin ring - you are stuck with the term on the right hand side without possibility to make it appear as part of the circulation of E, BECAUSE THE PATH INTEGRAL ON THE LEFT IS ALREADY COMPLETE AND THERE IS NOWHERE TO FIT THAT TERM. There is no jump at the terminals because the ring is not... a part (that can be made external) to the ring. [note]
When the CIRCUIT PATH ITSELF runs around a variable flux region, you cannot hide it inside a component accessible through its terminals, because IT IS YOUR FRIGGIN' CIRCUIT PATH, not a part of it. The circuit is unlumpable and you are stuck with Faraday's law. If you mathematically bring the rhs on the lhs, you cannot make it appear as some contribution on the loop ("auf dem Wege", in case you already forgot) for the circulation of E. It is invisible. All you can see are the contribution to the path integral: the drops at the resistors, the boosts at the batteries, the voltage at the thermocouple, the contribute of the solar cell, and of every other component you placed "auf dem Wege", which means 'on the way', along the path. Repetitia juvant, sometimes.
As I said before, it is unfortunate none of you KVLers have a long solenoid or a toroidal transformer because it would have been fun seeing you trying to locate the EMF contribution that's on the right hand side along the circuit path (remember "auf dem Wege"?)
[note] Yes, you can pull the math trick that McDonald uses, by converting the surface integral of B into the path integral of the magnetic vector potential A and then incorporate that into the path integral on the left-hand side. But that will give you the path integral of the conservative electric field Ecoul alone which does not completely describe the system (only half of it, so to speak).
The conservative PART Ecoul of the electric field E admits an electric scalar potential (which obeys what I would call Kirchhoff Scalar Potential Law, so that you KVLers can be happy with a dummy that resembles the high school rule you cannot do without), BUT you have to keep in mind that such potential alone does not completely describe the system. You need to supply the induced electric field Eind (or the vector potential A), that you just subtracted away. Moreover, the difference in scalar potential is not what is measured by a voltmeter, and you can't apply Ohm's law or Joule's heating law using the scalar potential difference alone (in the presence of variable magnetic fields).
Wow, interesting! Every book I have checked say the induced EMF is lumpable (for example, check the attached figure from Electromagnetics for Engineers by Ulaby).That's just dumb. The thing that is being "lumped" here is not the EMF, it's the electric potential that "builds up" along a path (of conductor) that is subjected to the EMF.
Wow, interesting! Every book I have checked say the induced EMF is lumpable (for example, check the attached figure from Electromagnetics for Engineers by Ulaby).That's just dumb. The thing that is being "lumped" here is not the EMF, it's the electric potential that "builds up" along a path (of conductor) that is subjected to the EMF.
Wow, interesting! Every book I have checked say the induced EMF is lumpable (for example, check the attached figure from Electromagnetics for Engineers by Ulaby).
"The transformer EMF is the voltage difference that would appear across the small opening between terminals 1 and 2, ..."
By the way, when you suggested the solution to the problem I posted, what is the first thing you do? You lumped the EMF!
At this point whom should we believe, the literature (and experiments) or Sredni?
Wow, interesting! Every book I have checked say the induced EMF is lumpable (for example, check the attached figure from Electromagnetics for Engineers by Ulaby).
You probably have checked fewer books than I have. Purcell does not say so. Ramo Whinnery and VanDuzer does not say so. Haus and Melcher does not say so. Brandao Faria does not say so...
Could it be that the books you checked were talking about lumped circuits?
Because that's what Hayt was doing - he was showing how to "amend KVL" to make it work with LUMPED inductors. (Edit: Components you access via their closed together terminals.)
And so does Ulaby. I have that book, as well, and in my edition that figure is in section 6.2 "Stationary loop in a time-varying magnetic field": it expressly references a lumped inductor which has terminals.Quote from: Ulaby"The transformer EMF is the voltage difference that would appear across the small opening between terminals 1 and 2, ..."
You know why the opening has to be small (and the terminals close together)? Because the circuit you put your component in has to be shrunk to a dimensionless point. Has to be lumped. Ulaby is talking about a lumpable circuit that is being lumped.QuoteBy the way, when you suggested the solution to the problem I posted, what is the first thing you do? You lumped the EMF!
No, I applied Faraday. I can do that even with lumpable circuits, if I choose not to lump them. Here's one picture from one of my answers on EE Stack Exchange where I properly apply Faraday to a lumpable RLC circuit (the 5 + 3 + 0 = 8 approach)
(https://i.stack.imgur.com/d43IA.png)
and here is how I can turn Faraday into "amended KVL" for the samecircuitsystem - which I now treat as lumped (the 5 + 3 - 8 = 0 approach) by using a circuit path that does not inclued the variable magnetic region
(https://i.stack.imgur.com/yIJqh.png)
If the circuit is lumpABLE I can treat is either as lumpED (applying 'extended KVL') or as NON lumped (applying Faraday).
If the circuit is UNlumpABLE, I am stuck with Faraday.
It's that simple. Really.QuoteAt this point whom should we believe, the literature (and experiments) or Sredni?
You could believe Purcell, Ramo Whinnery Vanduzer, Haus and Melcher, Faria, Romer, Roche, Nicholson, ... basically any professor who explicitly treated the general case, and did not limit their discussion to lumped circuits alone.
voltage between nodes A and D (VAD) which are half a circle apart.[/b]
As I've stated, the definition of that voltage is the very issue that is not agreed upon. So if you want a number for an answer, you have to specify your definition or method of measurement. One definition that might be interesting is the voltage measured by a voltmeter whose leads go in an exact straight line between the points. You would need a gap or hole in the inductor and core that are providing the magnetic flux, but that may be doable.
Or one could use the definition of voltage given by the International Electrotechnical Committe IEC 60050
https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=121-11-27 (https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=121-11-27)
and specify the path, as I did.
Wow, interesting! Every book I have checked say the induced EMF is lumpable
Wow, interesting! Every book I have checked say the induced EMF is lumpable
Nope. They don't say that. It's all in your head.
In that specific case, that EMF is lumpable because the geometry of the circuit allows it. The varying magnetic field is contained in a specific area of the circuit. What is omitted from that diagram is the path taken to calculate the EMF. The path doesn't encompass the area where the varying mag field is. Note also how the author says the loop is stationary.
If you say "Can't be known" then you're obviously using the wrong definition for volts.
If you say zero, then transformers have zero volts output, which is obviously false.
If you say non-zero, then Lewin goofed by not accounting for the voltage induced in his probe leads between the "point of measurement" and the "volt meter."
So what's the voltage across the two wire ends shown by the green path?
No, I applied Faraday. I can do that even with lumpable circuits, if I choose not to lump them. Here's one picture from one of my answers on EE Stack Exchange where I properly apply Faraday to a lumpable RLC circuit (the 5 + 3 + 0 = 8 approach)
(https://i.stack.imgur.com/d43IA.png)
Fantastic! Now here is another problem for you. The same 'Lewin' ring as before with a AA battery in series (as show in the attached figure). Compute the voltages V1 and V2 at t=0. Also, the battery, although slowly, is discharging over time, but at t=0 the voltage between the terminals of the battery 1.5V.
If you say "Can't be known" then you're obviously using the wrong definition for volts.
If you say zero, then transformers have zero volts output, which is obviously false.
If you say non-zero, then Lewin goofed by not accounting for the voltage induced in his probe leads between the "point of measurement" and the "volt meter."
So what's the voltage across the two wire ends shown by the green path?
I don't think the conclusions you draw from the possible answers are valid.
But I can also predict that you will not understand, and reject, the answer once given. :-DD
No, I applied Faraday. I can do that even with lumpable circuits, if I choose not to lump them. Here's one picture from one of my answers on EE Stack Exchange where I properly apply Faraday to a lumpable RLC circuit (the 5 + 3 + 0 = 8 approach)
(https://i.stack.imgur.com/d43IA.png)
Fantastic! Now here is another problem for you. The same 'Lewin' ring as before with a AA battery in series (as show in the attached figure). Compute the voltages V1 and V2 at t=0. Also, the battery, although slowly, is discharging over time, but at t=0 the voltage between the terminals of the battery 1.5V.
The solution is in the image you quoted. It's fascinating that you do not realize it.
Just switch the capacitor with a resistor, and there you will see how to apply Faraday to your circuit, and how the right hand side only features the induction EMF, while the battery EMF is accounted for as part of the circulation.
You really can't see it, if you think putting a battery in Lewin's ring can represent some sort of difficulty.
Anyway, I solved step by step (again for the general case, I am not interested in exercises) and I tried to spell out every single step - including sign conventions and the many parts you can break the circulation path integral (something you can read, certainly better explained in Ramo Whinnery and VanDuzer - but you won't read it, right?), and how the direction of the current depends on who wins between the induction EMF and the battery.
But before scanning these two pages, I want that some KVLer do the measurements I propose.
(Post to come tomorrow)
So let me ask you this. In the following diagram:
(https://i.postimg.cc/pXFDpYwk/deleteme.jpg)
Assume that the upper section encloses exactly half of the dB/dt, and that the wires are superconductors.
Also assume that the solenoid is infinitely long.
So what's the voltage across the two wire ends shown by the green path?
What you are telling me by making an equivalence from my circuit to your circuit is that you lumped the induced EMF and them you used KVL to solve it!
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
That is the root of the controversy. Everything else is noise.
Lewin thinks that this is the definition of KVL:
\$\oint_{}^{}E.dL=0\$
While this is the accepted definition of KVL (since at least 1909, the earliest reference I found, but must likely older than that):
\$emf=\oint_{}^{}E.dL=-\frac{d }{dt}\int_{S}^{}B.dS\$
I'm not saying that there are electric fields INSIDE a conductor, stationary or otherwise, that we know because the -∫E.dl=0 for a superconductor.
I am talking about the EMF across the ends of a wire according to -L(dI/dt), which Belcher clearly describes as being non-zero in a changing magnetic field even for a superconductor.
That should be the second thing you learned in your electromagnetism course out there.
Are you thinking there's a difference between a stationary wire in a dB/dt field, and a moving wire in a stationary and non-uniform B field?
What you are telling me by making an equivalence from my circuit to your circuit is that you lumped the induced EMF and them you used KVL to solve it!
You really can't see it, can you?
You're like that guy in Kevin Smith's "Mallrats" movie. The guy who spend hours in front of the stereoscopic poster and everybody else can tell what the image is, while he can't see it.
McDonald: ... He uses diversion and an obsolete version of a "law" to create an apparent paradox.
That is the root of the controversy. Everything else is noise.
Lewin thinks that this is the definition of KVL:
\$\oint_{}^{}E.dL=0\$
Aaaaaand Lewin is right. KVL holds for every circuit for which \$\oint_{}^{}E.dL=0\$. If you calculate \$\oint_{}^{}E.dL\$ and it results in zero, you can apply KVL blind-folded. You can even bet your life on it.
So it is ironic that in Lewin's world, KVL always holds. ALWAYS. The only thing you need to do is to find a path for which \$\oint_{}^{}E.dL=0\$ and you're good to go.QuoteWhile this is the accepted definition of KVL (since at least 1909, the earliest reference I found, but must likely older than that):
\$emf=\oint_{}^{}E.dL=-\frac{d }{dt}\int_{S}^{}B.dS\$
Uhh, nope. According to McDonald, this is the more accepted definition of KVL:
0 = ∑loop voltage drops = ∑iIiRr + ∑j( ̇Ij Lj + ∑k ̇IkMjk) + ∑l Ql/Cl −∑mEm (1)
And he remarks:
Lewin has also supplemented his lectures with two notes [34, 35], where is it claimed that Kirchhoff’s (2nd)
circuit law is that ∮loop E·dl= 0 for any circuit loop, rather than the more standard version, eq. (1), for
(coupled) R-L-C circuits.
Bold letters are mine.
So, it holds with the following caveats:
Caveat #1 Your circuit must be made exclusively of lumped components (R, L, C). I.e. it must be lumpable.
Caveat #2 Some unlumpable circuits can be solved by the equation (1), however the EMF can in no way be measured.
Caveat #3 It doesn't hold for whatever circuits where you have radiation.
Caveat #4 It doesn't hold for whatever circuits where its size is comparable to the wavelength.
Caveat #5 It doesn't take into consideration the self inductance of the rest of the circuit.
Caveat #6 While Lewin's version is absolutely precise. This version is an approximation.
Caveat #7 Mehdi says, however, that this "version" of KVL always holds. Which is not true.
Caveat #8 Mehdi is stupid.
Caveat #9 Stupidity is a moral issue. Not and intellectual one.
So, in Mehdi's world KVL doesn't always hold. The reason why it doesn't requires a little study, but Mehdi wants to convey the idea that you can be an instant expert in electromagnetism without the proper education. Welcome to the 21st century. I'm loving it.
If you say "Can't be known" then you're obviously using the wrong definition for volts.
If you say zero, then transformers have zero volts output, which is obviously false.
If you say non-zero, then Lewin goofed by not accounting for the voltage induced in his probe leads between the "point of measurement" and the "volt meter."
So what's the voltage across the two wire ends shown by the green path?
I don't think the conclusions you draw from the possible answers are valid.
But I can also predict that you will not understand, and reject, the answer once given. :-DD
So, you too have a crystal ball!
I'm not saying that there are electric fields INSIDE a conductor, stationary or otherwise, that we know because the -∫E.dl=0 for a superconductor.
I am talking about the EMF across the ends of a wire according to -L(dI/dt), which Belcher clearly describes as being non-zero in a changing magnetic field even for a superconductor.
Precisely. If you "walk" between the ends through the conductor, you will find zero volts. If you "walk" between the same ends, but now chosing the gap between the ends as your path, you'll find your non-zero voltage. These two voltages are different, although they refer to the same two points.
End of story. Have a good night's sleep.QuoteThat should be the second thing you learned in your electromagnetism course out there.
The sole purpose of an engineering degree is to able to debunk KVLers.
QuoteAre you thinking there's a difference between a stationary wire in a dB/dt field, and a moving wire in a stationary and non-uniform B field?
Before you set out to give answers on Youtube, learn to ask the proper questions.
So let me ask you this. In the following diagram:
(https://i.postimg.cc/pXFDpYwk/deleteme.jpg)
Assume that the upper section encloses exactly half of the dB/dt, and that the wires are superconductors.
Also assume that the solenoid is infinitely long.
So what's the voltage across the two wire ends shown by the green path?
Let's see if you can forecast my answer by looking at this image
(https://i.postimg.cc/15n8XGXJ/Voltage-can-be-path-dependent.jpg)
https://i.postimg.cc/15n8XGXJ/Voltage-can-be-path-dependent.jpg
Some hints:
What color would I use for that kind of path?
What color would I use for the probes in Lewin's setup?
Goodness you dodge and weave when asked questions.
But look at the diagram you provided. From that any reasonable person would conclude that the paths which do not collide with the core material, (i.e. either completely inside or completely outside) are lumped.
\$
\begin{array}{l}
V_2 = R_2 \cdot I = 900\Omega \cdot 1mA = 0.9V \\
V_1 = - R_1 \cdot I = - 100\Omega \cdot 1mA = - 0.1V \\
\end{array}
\$
As for VAD: any two nodes that are half a circle apart have half of the total EMF. In this case |VAD|=0.5V.
Goodness you dodge and weave when asked questions.
But look at the diagram you provided. From that any reasonable person would conclude that the paths which do not collide with the core material, (i.e. either completely inside or completely outside) are lumped.
You know, I don't think you know the meaning of lumped. You try to apply it to paths? What is a lumpable path? I apply it to circuits (you need to lump them, squeeze them to make them as small as a point, dimensionless) or components (same). And why can't you lump a circuit or a component that has a magnetic flux region inside? Because flux needs an area to have a meaning. You can't squeeze it into a point without losing meaning. That's the point (pun intended). But if the component has terminals close together...
But what is a 'lumped path'? Where did you heard of this?
A lumpABLE system can be considered lumpED or UNlumped depending on what you consider its circuit path. If the circuit path contains the magnetic flux region, you cannot squeeze it beyond the perimeter of that region. If the component contain the flux region, you take the terminals out, put them very close together so that they can occupy (so to speak) the space of a point on your circuit and attach them to a gap as wide as a point (so to speak) on your circuit path. Your circuit path, including the connection to the component, is now shrinkable to a point.
What the heck is a 'lumpable path'?
Here is the answer to your previous quiz
You talk about measuring reality, so this is my prediction for your circuit. If you don't like the polarities flip the signs.
(https://i.postimg.cc/R04QGyHs/KVL-works-if-I-leave-out-the-magnetic-region.jpg)
https://i.postimg.cc/R04QGyHs/KVL-works-if-I-leave-out-the-magnetic-region.jpg
Note that you won't be able to measure any voltage in the perfectly conducting wire of the ring, in accordance with Ohm's law. So, are you a lumper, or today you decide that there is voltage in the wires and in the probes? I have to ask.
Now, it's my turn.
Same circuit (you can even use a single resistor if you want. My prediction is that you will observe zero volts in the wires even when the sliders (you sliding the probe tips along the ring) get in contact inside the core.
So how does KVL "appear" to hold?
(https://i.postimg.cc/cH5RxJ52/KVL-dies-if-the-magnetic-region-is-inside-my-circuit-path.jpg)
https://i.postimg.cc/cH5RxJ52/KVL-dies-if-the-magnetic-region-is-inside-my-circuit-path.jpg
Now, if today you are still a lumper, please tell me where is the EMF on the ring.
That's precisely your, Mehdi's, Dave's and everybody-else-that-insist-that-KVL-always-hold's mistake.
KVL says that the voltages measured along the path of a mesh add up to zero.
But Lewin showed at least one circuit where the voltages do not add up to zero.
Therefore KVL doesn't always hold. Period.
There's nothing you can do to remedy this. It is not about Lewin. It is the way nature works. Go to your lab, set up the same experiment, measure the voltages around the circuit and see for yourself. We are glad that those who repeated the experiment were precisely the guys who thought that Lewin had somehow cheated or blundered the experiment.
They're all dead inside now. All of them.
You cannot solve such circuit using KVL. It is impossible. You'll have to resort to the full monty and use Maxwell's equations at least to calculate the EMF produced by the varying magnetic field.
After that, you can of course devise an equivalent circuit where instead of a varying magnetic field producing the extra EMF upon the entire circuit, you have a battery, a generator, a transformer, or any other equivalent lumped (i.e. localized) component to produce the same EMF and get the exact same effect on the other components. In that case, you can solve the equivalent circuit using KVL because you theoretically removed the varying field from the circuit and stashed it away in the equivalent component.
But that is just a theoretical trick that has a lot of caveats.
One of them is that you will not find this extra EMF on the circuit. Not even if you fart your way through the Bohemian Rapsody.
So how's that possible? How can we have, so to speak, a spooky "component" that produces an EMF in a circuit, but is not present there? This seems to violate the principle of conservation of energy, doesn't it? Those are legit questions. But to answer them you need to abandon KVL, which these people are not prepared to accept. To reconcile their cognitive bias with the real phenomenon that contradicts it, they create all the irrational arguments I listed above and more.
KVL says that the voltages measured along the path of a mesh add up to zero.
But Lewin showed at least one circuit where the voltages do not add up to zero.
One of them is that you will not find this extra EMF on the circuit. Not even if you fart your way through the Bohemian Rapsody.
So how's that possible? How can we have, so to speak, a spooky "component" that produces an EMF in a circuit, but is not present there?
Too bad you didn't get an engineering degree, you might have been able to debunk KVLers if you had! :-DD
I know the right questions to ask, but you won't answer them.
\$
\begin{array}{l}
V_2 = R_2 \cdot I = 900\Omega \cdot 1mA = 0.9V \\
V_1 = - R_1 \cdot I = - 100\Omega \cdot 1mA = - 0.1V \\
\end{array}
\$
As for VAD: any two nodes that are half a circle apart have half of the total EMF. In this case |VAD|=0.5V.
I see you used Ohm's law to compute the voltage drop along the resistors. So Ohm's law works. Wonderful.
Can you apply Ohm's law to compute the voltage drop across the wire that goes from R1 to point A?
Because we know that from A to D we have a voltage of half a volt, while across R1 we have what 0.1 V (fix the signs as you please while I put popcorns in the microwave). So, what gives?
(you can use the resistivity of copper, or a very low resistance for the wires, for example 1 milliohm, if zero resistance is a problem)
Too bad you didn't get an engineering degree, you might have been able to debunk KVLers if you had! :-DD
The bogus claims of your nonsense “experiments” were debunked fair and square 9 days ago. Since then you have been trying to conduct “interviews” with forum members to see if you can somehow disqualify them. Let me tell you, it’s not working.QuoteI know the right questions to ask, but you won't answer them.
Your questions be like “Wait a minute! Do you believe tomatoes are not animals?”
We can’t help you.
Jesse Gordon knows what he is talking about!
How do you expect me to take you seriously when you don't know the circuital difference between a resistor and a voltage source?
Jesse Gordon knows what he is talking about!
We also know what he’s talking about.
How do you expect me to take you seriously when you don't know the circuital difference between a resistor and a voltage source?
The problem is that wires don’t make that distinction. So, you’re not gonna be fool enough to make it.
You don't even know the basics of electric circuits.
That is the problem of arguing with somebody whose fundamentals are not there.
Again, you're quoting me out of context.
I see you noticed that you made the same mistake Lewin did and you got one of the volt meters backwards, but at least you caught it in time to put a text note that says I can flip the volt sign.
So yes, I'd like to flip the sign on the left-hand meter which reads 1V. You have to keep the meters all pointing clockwise or counter clockwise -- but all the same way for a given test -- around the loop. That's just the way KVL is. If you mix up your volt meter signs even with pure batteries and resistors, KVL will appear to fail then too.
You clearly show different possible paths within the element, the 5v and 0v paths inside that element are unambiguous, unvarying, and if that is the path in that element, then it can be considered a lumped element in a KVL loop and KVL will hold.
\$
\begin{array}{l}
V_2 = R_2 \cdot I = 900\Omega \cdot 1mA = 0.9V \\
V_1 = - R_1 \cdot I = - 100\Omega \cdot 1mA = - 0.1V \\
\end{array}
\$
As for VAD: any two nodes that are half a circle apart have half of the total EMF. In this case |VAD|=0.5V.
I see you used Ohm's law to compute the voltage drop along the resistors. So Ohm's law works. Wonderful.
Can you apply Ohm's law to compute the voltage drop across the wire that goes from R1 to point A?
Because we know that from A to D we have a voltage of half a volt, while across R1 we have what 0.1 V (fix the signs as you please while I put popcorns in the microwave). So, what gives?
(you can use the resistivity of copper, or a very low resistance for the wires, for example 1 milliohm, if zero resistance is a problem)
This is, by large, the most telling evidence of your ignorance of what is going on in the circuit (or any circuit by that matter!) in the whole thread. How do you expect me to take you seriously when you don't know the circuital difference between a resistor and a voltage source? That was explained before in this thread several times so I'll not do it again.
\$
\begin{array}{l}
V_2 = R_2 \cdot I = 900\Omega \cdot 1mA = 0.9V \\
V_1 = - R_1 \cdot I = - 100\Omega \cdot 1mA = - 0.1V \\
\end{array}
\$
As for VAD: any two nodes that are half a circle apart have half of the total EMF. In this case |VAD|=0.5V.
I see you used Ohm's law to compute the voltage drop along the resistors. So Ohm's law works. Wonderful.
Can you apply Ohm's law to compute the voltage drop across the wire that goes from R1 to point A?
Because we know that from A to D we have a voltage of half a volt, while across R1 we have what 0.1 V (fix the signs as you please while I put popcorns in the microwave). So, what gives?
(you can use the resistivity of copper, or a very low resistance for the wires, for example 1 milliohm, if zero resistance is a problem)
This is, by large, the most telling evidence of your ignorance of what is going on in the circuit (or any circuit by that matter!) in the whole thread. How do you expect me to take you seriously when you don't know the circuital difference between a resistor and a voltage source? That was explained before in this thread several times so I'll not do it again.
Good: "the soldier that flees is good for another battle".
Can you shed some light on when exactly the wire becomes a 'voltage source'? Do you believe, like Jesse Gordon, that the wires acquire this magical voltage when they cross the magic portal of the core, or are they always voltage sources? For examples, is a quarter turn wire (open, just a quarter turn) a voltage source when it is inside the hole of the toroidal core? Does it ceases to be a voltage source when it is in front of the toroidal core but does not pass through the hole in the donut?
Teach me.
This has already been done. The video by "Silicon Soup" has been linked in this thread at least twice. It is a very good video as it also shows the electric field component, without which you can not understand the problem at all.
How do you expect me to take you seriously when you don't know the circuital difference between a resistor and a voltage source?
The problem is that wires don’t make that distinction. So, you’re not gonna be fool enough to make it.
Before this thread you knew nothing. Sadly, there is no progress. That is the problem of arguing with somebody whose fundamentals are not there.
That is the problem of arguing with somebody whose fundamentals are not there.
I’m not versed in pseudo science. Sorry.
You don't even know the basics of electric circuits.
Says every single debunked KVLer.
I guess this problem could be modeled and solved using a 3D EM-simulator/solver. Then we could say: Case closed.
Any 3D EM-simulator gurus here?
Again, you're quoting me out of context.
So many words that have nothing to do with the actual discussion. It's as if you were trying to create a smoke screen to hide the inconsistencies in your approach. The problem is that in almost every paragraph you write there is either a wrong concept, or a misconception, or a red flag betraying your limited knowledge. And the same is true for the two very long posts you wrote yesterday. I will try to collect all (well, most) the misconceptions and the false statement in separate posts by category, so that instead of an endless tit for tat, other users can benefit from a more organic discussion.
Let's start with a simple red flag.
Don't be afraid of the signs!
Regarding the following part of my picture, you wrote (emphasis mine):
(https://i.postimg.cc/B6WVgpBm/screenshot-21.png)
https://i.postimg.cc/B6WVgpBm/screenshot-21.png
QuoteI see you noticed that you made the same mistake Lewin did and you got one of the volt meters backwards, but at least you caught it in time to put a text note that says I can flip the volt sign.
So yes, I'd like to flip the sign on the left-hand meter which reads 1V. You have to keep the meters all pointing clockwise or counter clockwise -- but all the same way for a given test -- around the loop. That's just the way KVL is. If you mix up your volt meter signs even with pure batteries and resistors, KVL will appear to fail then too.
Dude, seriously? You cannot handle the relativity of polarities? Apart from the fact that we are using voltmeters in an AC circuits, so the phase information is lost on us... what problem can you have in a circuit with batteries if one voltmeter is flipped? If it measure -0.5V with the probes in that position, it will measure +0.5V with the probes inverted.
You know I can choose whatever sign I want for the current in a circuit, then solve for its value and if it comes down negative it just means that it is flowing in the opposite direction to the one I supposed at first?
I hope you know at least some of the basic, such as how a current divider works, or what it means to load or shunt a generator, because otherwise this will be a very long discussion.
You dragged the discussion we were having here down about ten notches.
The ambiguously 'unambiguos' voltages in the two branches
Jesse, referencing this figure
(https://i.postimg.cc/VvFWycbH/Voltage-can-be-path-dependent.jpg)
You wrote (still showing you do not understand what the term 'lumped' really means, but I will get to that in a later, dedicated, post):You clearly show different possible paths within the element, the 5v and 0v paths inside that element are unambiguous, unvarying, and if that is the path in that element, then it can be considered a lumped element in a KVL loop and KVL will hold.
It appears you are referencing the bottom figure, where both 5V and 0V paths are present. Good, Let's forget about the 'ambiguous' orange paths and let's focus on the unambiguous green (5V) and purple (0V) paths. Well, the path in the left branch of the circuit is a purple path that has the unambiguous voltage of 0V; the path in the right branch of the circuit is a green path that has the unambiguos voltage of 5V.
What exactly is the excuse you invoke to deny that two branches of the same circuit, with the same starting and ending points will have different values for the unambiguos voltage associated to the path that goes through them?
This has already been done. The video by "Silicon Soup" has been linked in this thread at least twice. It is a very good video as it also shows the electric field component, without which you can not understand the problem at all.
Thanks! Checked the video once, and looks really good. I need to dedicate more time watching it again doing the math.
You have to keep the meters all pointing clockwise or counter clockwise -- but all the same way for a given test -- around the loop. That's just the way KVL is. If you mix up your volt meter signs even with pure batteries and resistors, KVL will appear to fail then too.
...
I complained about you putting the sign wrong on the "LEFT-HAND meter which reads 1V" and you zoom in on the RIGHT HAND meter which reads 1V?
But it just so happens that when applying KVL, you have to have all the volt meters pointing the same clock direction around the loop,
Lewin ALSO made this same error, having one of HIS volt meters backwards when he purported to measure test KVL. That's why one of his scopes read a positive spike and the other read a negative spike.That's not an error. It's a no brainer to automatically flip the signs in your head when the loops are these simple.
Fine, let's talk about the actual discussion, if you will:
In the diagram below, assuming that all of the volt meters are polarity-clocked the same way, and assuming you ignore the 0.5v meters, will KVL hold?
I guess this problem could be modeled and solved using a 3D EM-simulator/solver. Then we could say: Case closed.Simulators are a wonderful thing, but we should not neglect real-world observed data either.
Any 3D EM-simulator gurus here?
Here I test ---
Can you shed some light on when exactly the wire becomes a 'voltage source'? Do you believe, like Jesse Gordon, that the wires acquire this magical voltage when they cross the magic portal of the core, or are they always voltage sources? For examples, is a quarter turn wire (open, just a quarter turn) a voltage source when it is inside the hole of the toroidal core? Does it ceases to be a voltage source when it is in front of the toroidal core but does not pass through the hole in the donut?
Teach me.
I guess this problem could be modeled and solved using a 3D EM-simulator/solver. Then we could say: Case closed.Simulators are a wonderful thing, but we should not neglect real-world observed data either.
Any 3D EM-simulator gurus here?
Here I test ---
I am sorry to interrupt your victory lap, but... the same circuit you says it shows that KVL 'appears' to hold, is actually breaking it.
https://i.postimg.cc/9MW4fCCd/screenshot-23.png
(https://i.postimg.cc/9MW4fCCd/screenshot-23.png)
Here is the detail.Again, you are trying to measure the transformers OUTPUT from WITHIN the transformer.
(https://i.postimg.cc/QCQnJQRG/screenshot-22.png)
https://i.postimg.cc/QCQnJQRG/screenshot-22.png
And in case you are trobled with the magical entrance of the voltage stargate, here is Lewin's ring itself, with voltmeters all around it, showing that KVL 'appears' to die. Horrible death, poor creature.
(https://i.postimg.cc/9MRf0Msq/screenshot-24.png)
https://i.postimg.cc/9MRf0Msq/screenshot-24.png
(https://i.postimg.cc/bw7CWFpc/screenshot-25.png)
https://i.postimg.cc/bw7CWFpc/screenshot-25.png
Does anybody really know what we're actually arguing about here?
I Think we all agree that a transformer's output winding works fine (or at least measures fine) as an element in a mesh which works with KVL.
That is to say, I don't think anybody is saying that a transformer output cannot be an element in a KVL mesh.
And yet, getting clarification on that is nearly impossible. Nobody wants to exactly confirm nor deny that. And why no? I don't know.
If it's not about a transformer secondary winding's acceptability as an element in a KVL mesh, what then?
Many of the examples given for "KVL failing" are not meshes, but rather multiple nested loops with multiple voltage sources and sinks, and various parts are being cherry picked to give the appearance of KVL failing. Of course KVL doesn't appear to work with any circuit if you are modeling one thing and measuring a functionally different topology.
Then there is talk about there being no electric field along a wire. But we're not talking about an electric field near the surface of the wire, we're talking about the voltage difference between winding ends (or in some cases center taps or other part-way-taps) of a transformer winding -- actual electrical connections to the winding, either at the ends, or at some points between the ends.
The fact is, when we measure the voltage across the ends of a secondary winding, we measure a voltage. If we have a center tap, we can measure voltage there too.
And if we place our super sharp probe at any point along the winding, it forms an instant electrically connected tap that works just like a manufacturer produced tap, and again, we measure the voltage that we would expect.
Or are we arguing about whether certain transformer types can be probed accurately? Does a difficulty in probing mean there is no voltage there to be measured?
What's odd is that this is not the first conversation I've had about this. Since uploading my Lewin Clock video, I have had some exceedingly long discussions about it, quite probably with people who were more educated than any of us here, but the story was the same - a strong hesitance to answer actual real life questions. I also asked them like "What is it exactly, are we just using different definitions for something and we don't know it?" But they could not explain what we were arguing about either.
There were many many things they could not answer. That's why I ended up making my Lewin Clock and Iron Core videos - because people told me things would be a certain way and I didn't believe them, so I tested, and I was right and they were wrong, so I made a video to show them.
It seems as soon as I try to zero in on one issue, the other guy switches to another. As soon as I try to zero in on the new topic, again, he switches to yet another. It's like a 3 ring circuits.
But there is ONE thing that these people do know, without a shadow of a doubt:
In the words of Silicon Soup, "OF COURSE LEWIN IS RIGHT!"
Is that what this is all about?
What is it we're ACTUALLY arguing about? Why are the Lewinites so unwilling to admit to the observable facts so that we can then concentrate on the more difficult parts of the issue?
EDIT/PS: And I often wonder if the issue comes down to the difference in meaning of -∫E.dl and ∮E.dl. Are we all just falling for the "Common misconception" that Dr. Belcher talked about in assuming that ∮E.dl=0, or that the -L(dI/dt) voltage read by the voltmeter represents a -∫E.dl through the inductor? But alas, this has been brought up, and that seems not to help either.
I think it boils down to the assertion: "KVL doesn't hold in non-conservative fields". Maybe that was the case in the early to middle 1800s
I think it boils down to the assertion: "KVL doesn't hold in non-conservative fields". Maybe that was the case in the early to middle 1800s
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Now, I have to check with the kitchen, but I am pretty sure I have deja-vus:
(https://i.postimg.cc/0jhNjDdL/screenshot.png)
We already had this discussion on how those pages from Hayt are about the "amended" or "extended" or "new" KVL. Haven't we? Three years have passed, and you still have to understand that it's a couple of centuries we know we can apply a 'modified' version of KVL to circuits with inductors and other magnetic components. The trick is to hide the magnetic flux inside the component SO THAT THE CIRCUIT PATH CAN SKIP ITS INNARDS AND WE AVOID TO HAVE VARIABLE FLUX LINKED BY OUR CIRCUIT PATH.
You really, really, really CAN NOT UNDERSTAND this simple concept.
Yoo probably lack basic vector algebra skill, maybe you were ill when they explained why you can define a potential function when a vector field is conservative, or like Stoke's theorem it is just beyond you, I can't tell. But you ignore basic math and basic physics - and now you are desperately twisting your epicycloids to explain the retrograde motion of Mars. If you only could understand Newton's theory of gravitation...
You call "BS" the standard theory of classical electrodynamics because you did not study it well enough to understand that your 'tiny batteries in series' model is not a model of the complete system, but just of the mathematical portion that is conservative. Look at the "Map of the Ring Quest" picture I've posted yesterday: do you recognize your model in the rhs?
After I have scanned a few images, I will make a dedicated post to explain what you have done, how you can see it by manipulating the integral vector equations, and why that model is not a model of your system but only of a part of it.
Here's what my crystal ball forecasts:
You will cursorily read it. You will not understand it. And three years from now, you will still be unable to tell the difference between lumped circuits (to which you can apply 'extended KVL' like Hayt and Ulaby show) and unlumpable circuits (for which not even the 'extended' version of KVL works BECAUSE THE ********** CHANGING FLUX IS LINKED BY YOUR ******* CIRCUIT PATH)
Ahh yes you three guys and your crystalballs! What gives? I have a pair of 200mm crystalballs, some 100's and some 80's, and they don't work near as good as yours!I think it boils down to the assertion: "KVL doesn't hold in non-conservative fields". Maybe that was the case in the early to middle 1800s
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Now, I have to check with the kitchen, but I am pretty sure I have deja-vus:
(https://i.postimg.cc/0jhNjDdL/screenshot.png)
We already had this discussion on how those pages from Hayt are about the "amended" or "extended" or "new" KVL. Haven't we? Three years have passed, and you still have to understand that it's a couple of centuries we know we can apply a 'modified' version of KVL to circuits with inductors and other magnetic components. The trick is to hide the magnetic flux inside the component SO THAT THE CIRCUIT PATH CAN SKIP ITS INNARDS AND WE AVOID TO HAVE VARIABLE FLUX LINKED BY OUR CIRCUIT PATH.
You really, really, really CAN NOT UNDERSTAND this simple concept.
Yoo probably lack basic vector algebra skill, maybe you were ill when they explained why you can define a potential function when a vector field is conservative, or like Stoke's theorem it is just beyond you, I can't tell. But you ignore basic math and basic physics - and now you are desperately twisting your epicycloids to explain the retrograde motion of Mars. If you only could understand Newton's theory of gravitation...
You call "BS" the standard theory of classical electrodynamics because you did not study it well enough to understand that your 'tiny batteries in series' model is not a model of the complete system, but just of the mathematical portion that is conservative. Look at the "Map of the Ring Quest" picture I've posted yesterday: do you recognize your model in the rhs?
After I have scanned a few images, I will make a dedicated post to explain what you have done, how you can see it by manipulating the integral vector equations, and why that model is not a model of your system but only of a part of it.
Here's what my crystal ball forecasts:
You will cursorily read it. You will not understand it. And three years from now, you will still be unable to tell the difference between lumped circuits (to which you can apply 'extended KVL' like Hayt and Ulaby show) and unlumpable circuits (for which not even the 'extended' version of KVL works BECAUSE THE ********** CHANGING FLUX IS LINKED BY YOUR ******* CIRCUIT PATH)
Does anybody really know what we're actually arguing about here?
I think it boils down to the assertion: "KVL doesn't hold in non-conservative fields".
Once you see it, you can't unsee it. That's why you see a lot of KVLers turn to Faradians, but never a Faradian turn KVLer.
Once you see it, you can't unsee it. That's why you see a lot of KVLers turn to Faradians, but never a Faradian turn KVLer.
Suuure! In the attached figure is the definition of KVL from the book Electromagnetics by Branislav M. Notaros. Go argue with the author of that book too!!! By the way, why did you use the very same definition of KVL to solve the problem I proposed before?
Once you see it, you can't unsee it. That's why you see a lot of KVLers turn to Faradians, but never a Faradian turn KVLer.
Suuure! In the attached figure is the definition of KVL from the book Electromagnetics by Branislav M. Notaros. Go argue with the author of that book too!!! By the way, why did you use the very same definition of KVL to solve the problem I proposed before?
You still do not understand, do you?
Well, I don't have that book, but my take is that the author is talking about lumped circuits.
For lumped circuits the circulation of E is zero. Then you can break up the integral into the 'passive' and 'active' parts, the rhs still being zero. Now, by the sheer power of mathematics you can put the parts of the circulation integral corresponding to the passive portions on the left (or the right, if you wish) and the parts of the circulation integral corresponding to the active portions on the right (or the left, if you wish).
All these parts are PART OF THE ONE AND ONLY CIRCULATION OF THE TOTAL ELECTRIC FIELD.
When you have electromagnetic induction, if your circuit is lumpable you can choose
1- to not lump it
then your circuit path goes through the component and your circuit path encloses the magnetic region.
You have to apply faraday and end up with A COMPLETE CIRCULATION PATH INTEGRAL ON THE LEFT, and A SURFACE INTEGRAL ON THE RIGHT.
2- to lump it
you change the circuit path for your circuit: yuo no longer pass throught the component, but JUMP AT THE TERMINALS. Now your new circuit path (for the same physical circuit) skips the magnetic region that can be hidden inside the component. You access the component through the terminals, that's the part of the circulation path that JUMPS from one terminal to the other. So, now the effect of your lumped component is ACCOUNTED FOR IN THE PATH INTEGRAL ON THE LEFT.
And these two methods work for lumpABLE circuit that can be considered at will either lumpED or NOT lumped.
But when you deal with circuits whose circuit path IS REQUIRED TO CONTAIN THE MAGNETIC REGION IN ITS INTERIOR you no longer can afford the luxury of lumping it and treat it as a lumped circuit.
NO MORE KVL.
ONLY FARADAY.
I will make a post "Lumpable (lumped and not lumped) and unlumpable circuits for Dummies"
And I forecast you will still not understand it.
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
I didn't subtract, I measured.
[...]
I didn't make up any framework. I just used my volt meter, resistors, and transformers to find out what observable reality is.
[...]
My level-1 "framework" is what I observe. Above that I do my best to understand what's going on at a theoretical level. Maxwell, Faraday, and Kirchhoff described it elegantly. I have no problem with any of them.
You know, it's funny that you keep asking the same question, after I already gave you the answer. Like jesuscf that keeps reverting back to the 5 + 3 + 0 = 8 vs 5 + 3 - 8 = 0 dichotomy for lumpable circuits (that can be treated as lumped or unlumped, depending on what circuit path we choose), and completely disregarding the unlumpable circuits it cannot be applied to.
Guys...
IT'S A SAILBOAT!
(http://www.austinchronicle.com/binary/3015/maxresdefault__6_.jpg)
Then I will make a post where I collect a selection of the misconceptions you keep writing in your long replies. Just to show you are making up rules that are in your head only.
I also intend to show you what you are measuring with your Lewin Clock. I already wrote that in a reply to jesuscf but I feel you need pictures with vivid colors.
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
And I forecast you will still not understand it.
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
If both your theory and experiments depend on each other, that'll do you no good.
Because the experimental data presented here was obtained by more or less blindly poking around circuits with a volt meter, and without any understanding of what is actually going on. So the measurements taken do not support in any form the claim that "KVL holds".
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
It really is their religion, isn't it? I hate to say it, but that seems to be what it comes down to.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
If both your theory and experiments depend on each other, that'll do you no good.
Because the experimental data presented here was obtained by more or less blindly poking around circuits with a volt meter, and without any understanding of what is actually going on. So the measurements taken do not support in any form the claim that "KVL holds".
I didn't subtract, I measured.
[...]
I didn't make up any framework. I just used my volt meter, resistors, and transformers to find out what observable reality is.
[...]
My level-1 "framework" is what I observe. Above that I do my best to understand what's going on at a theoretical level. Maxwell, Faraday, and Kirchhoff described it elegantly. I have no problem with any of them.
So, what Jesse does is poking around a circuit with a volt meter without having an idea what it's going to show, and as he sees the measurements he makes up some explanations but doesn't validate them against established science.
In fact he doesn't understand Maxwell-Faraday beyond the level of "volts per turn"
and especially doesn't understand that the equation describes a relation between the magnetic flux in the core and an (rotational, non-conservative) electric field around the core that is extending to infinity,
this being the reason why there cannot be an "inside" or "outside" of a transformer as he understands it. He doesn't realize it is this electric field that is separating charges in a path of conductor and causing "voltage" and that one needs to consider paths through this electric field to see if a loop of wire is a "transformer secondary" or not. Thus all the conclusions he derives from his observation are worthless.
Allow me to elaborate. Below picture shows the problem I gave Jesse to evaluate. It is a toroidal core with "1V of EMF per turn". A ring of resistors is around the core. One has double the value of the other. Volt meters are connected as shown and all numbers were provided by him. I have only added one additional volt meter showing "2/3V" to demonstrate my point. I've tried visualizing the electric field component with green arrows. RED loops are "hot", voltage is induced (1V). BLUE loops are "cold", no voltage is induced. I took over Jesses notation of a "signed voltage" which here means "phase", because obviously this is all AC and there is no "sign" on a RMS volt meter. But I guess he measured with an oscilloscope and found that the voltage is "inverted" in relation to the voltage across the other resistor.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1331327)
Now, to see why the blue loops are indeed cold one needs to know a tiny bit of vector calculus, or just accept the fact that all electric field components along any of the blue loops sum up to zero, in other words:
$${\oint{\mathrm{E}\;\mathrm{d}l} = 0}$$
That looks familiar.
With this in mind it should be easily visible why the red loops are "hot", because the electric field components do not sum up to zero:
$$\oint{\mathrm{E}\;\mathrm{d}l} = -\frac{\mathrm{d}B}{\mathrm{d}t},\; (\mathrm{= EMF = 1V})$$
This should also look familiar.
This tells us that in the blue loops there is no contribution from the magnetic flux in the transformer core and the volt meters in any of them display only what results from the electric currents flowing. That explains why we have 1/3V, 0V, 0V and 2/3V, Ohm's Law lets us expect that. They also sum up to the EMF of 1V which we should expect to find according to Mr. Faraday. These blue loops are those where KVL holds.
Now lets walk through both red loops clockwise. In the R+2R loop the path is with the curl of the electric field, in the 2R loop the path is against the curl, so lets just say we expect an EMF of "-1V" along this path and run with that simplification. We know that the electric field across 2R is 2/3V (measured along a "cold" path) and the EMF is "-1V" and when we sum that up we get to the "-1/3V" that Jesse's magic phase-aware volt meter was showing. Note that I am sticking with Jesse's frame of reference on purpose to explain what he "measures", being fully conscious that it is not a full analogy.
This analysis explains all the measurements without making anyone unhappy except Mr. Kirchhoff, but we can easily accept that, given that the more fundamental laws by Mr. Ohm and Mr. Faraday are satisfied. Jesse's claim that "KVL holds" because all the voltages "sum up to 0" is without basis because of a faulty interpretation of the results obtained.
Now the big question is of course, can KVL be somehow made to work in this arrangement, and for that we need to find an equivalent circuit with lumped elements. That will prove to be difficult, because one cannot find a place where to stick a lumped transformer winding or voltage source and still satisfy all the measurements taken in the various places. We can obviously not put it in the wires between the resistors, because we measure 0V across them. It can also not be in "R" and/or in "2R". If we put a 2/3V source "inside" 2R, that would violate the "-1/3V" reading on the rightmost volt meter.
So, where is it? Apparently it is there, but we cannot pinpoint it and measurements between two identical points show different results depending on how we instrument the circuit (1/3V, 2/3V, -1/3V). For circuit theory and KVL this is a nightmare. That's why there are "equivalent circuits" e.g. for transformers which try to model physics with lumped elements full of imaginary numbers and "magic items" like ideal transformers because they relieve engineers of having to think about physics. And to make KVL work. But now and then, when Sir James Clerk Maxwell makes an appearance, everyone is baffled why their circuits don't work.
Lumpable (lumped and not lumped) and unlumpable for Dummies
What makes a circuit lumpable? First of all its physical dimension have to be negligible compared to the wavelength of the electrical oscillations, and then voltages and currents 'offered' at the terminals must be well defined at any time. You want your circuit to be independent on how you measure voltage between two points or current along the same branch.
Here is a snapshot from page 2 of "Basic Circuit Theory", by Desoer and Kuh (don't let the title deceive you: this is the Bentley of circuit theory books).
([url]https://i.postimg.cc/76mcdQNg/Desoer-Kuh.jpg[/url])
Source: Desoer, Kuh "Basic Circuit Theory"
[url]https://i.postimg.cc/76mcdQNg/Desoer-Kuh.jpg[/url]
Note: in the case of Lewin's ring we know that the frequency is so low that retardation effects play no role; the condition that voltages and current be well defined is what we must be careful about. In particular, it's voltage the variable in discussion.
If we can interact with the component only through its terminals and we are not allowed to get inside, the only paths along which we can evaluate voltage (which is a path integral) are those 'outside' the component. And we require that the voltage be the same no matter how we choose the path joining the terminals.
In the case of magnetic components, we know that voltage along the path joining two points depends on the path, when we can go from one side of the magnetic flux region to the other. This is a direct consequence of one of Maxwell's equations (Faraday's law: curl E = -dB/dt) and basic vector integral calculus (Stokes theorem, the definitions of circulation and the definition of flux).
In order for voltage to be well defined, we must avoid paths that go through or 'on the other side' of the variable magnetic flux. The reason is simple: if the same starting and ending points admit two paths that are on opposite sides of the magnetic region, then the closed path formed by joining these two paths will enclose a variable flux and they must necessarily sum up to a nonzero value
Fig. two paths and the area enclosed (to be added later)
Now we know how to make voltage unique: allow only paths that cannot get into the forbidden zone. We enclose the component inside a black box (or an impenetrable wall) and we do not question what is inside. We must also ensure that our circuit path - the orange dashed line - does not contain variable magnetic flux itself.
Here is a lumpable circuit. The same circuit can be considered
- lumpED, when we avoid the forbidden paths by erecting an impenetrable wall and we only access the magnetic component through its terminals (note the circuit path that does not go into the forbidden zone, but instead jumps at the terminals). KVL works inside the green circuit path.
- NOT lumped, when we consider a circuit path (for the same physical system that we usually address with the name 'circuit') that encloses part or all of the variable magnetic flux region. In this case any path inside the orange dashed line that represent the circuit's premises is allowed. Some of these paths - not all, but only one would suffice - can 'go on the other side' of the magnetic region, making voltage between two points NOT WELL DEFINED.
([url]https://i.postimg.cc/8kFQxNqc/Lumpable-can-be-lumped-or-not.jpg[/url])
Fig. the same lumpable circuit can be considered either lumped or not lumped
[url]https://i.postimg.cc/8kFQxNqc/Lumpable-can-be-lumped-or-not.jpg[/url]
So far, so good: it looks like we have freedom to choose when we can make KVL works.
NO. There are circuits that are not lumpABLE. There are circuits where the circuit path is REQUIRED by definition or physical constraint to include the variable flux region. In this case it is not possible to find a green circuit path that connects the lumped components AND does not contain the variable flux region at its interior. Only orange paths are available.
Lewin's ring is an example of such a circuit. The resistors R1 and R2 are required to be on the opposite sides of the solenoid, i.e. the variable flux region. And you cannot find a circuit path that connects them without enclosing such forbidden zone. Voltages for points on your circuit will be path dependent.
([url]https://i.postimg.cc/NfhVVT6C/Unlumpable-circuit.jpg[/url])
Fig. an unlumpable circuit: you cannot exclude dB/dt region from the circuit path
[url]https://i.postimg.cc/NfhVVT6C/Unlumpable-circuit.jpg[/url]
And, no. You cannot model it with several tiny little transformer secondaries distributed along the perimeter, because you would forfeit the constraint that the two resistors be on the opposite sides of the variable magnetic region. It's exactly that constrain - your circuit path containing the dB/dt region - that makes Lewin's ring so special.
If you change the magnetic field region you are considering a different problem
([url]https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png[/url])
Fig. an unlumpable circuit: you cannot exclude dB/dt region from the circuit path
[url]https://i.postimg.cc/YCKNjzg2/Spot-the-differences.png[/url]
In order to model it with two or four lumped coils, the magnetic field region must be split to accommodate a circuit path that does not include any of it. I used the same 'stellated' path style used by Feynman in figure 22-9 on page 22-7 of his second volume of lectures.
Lumpable (lumped and not lumped) and unlumpable for Dummies
What makes a circuit lumpable? First of all its physical dimension have to be negligible compared to the wavelength of the electrical oscillations, and then voltages and currents 'offered' at the terminals must be well defined at any time. You want your circuit to be independent on how you measure voltage between two points or current along the same branch.
Here is a snapshot from page 2 of "Basic Circuit Theory", by Desoer and Kuh (don't let the title deceive you: this is the Bentley of circuit theory books).
(https://i.postimg.cc/sf4j3HbF/Desoer-Kuh.jpg)
Source: Desoer, Kuh "Basic Circuit Theory"
https://i.postimg.cc/sf4j3HbF/Desoer-Kuh.jpg
Note: in the case of Lewin's ring we know that the frequency is so low that retardation effects play no role; the condition that voltages and current be well defined is what we must be careful about. In particular, it's voltage the variable in discussion.
If we can interact with the component only through its terminals and we are not allowed to get inside, the only paths along which we can evaluate voltage (which is a path integral) are those 'outside' the component. And we require that the voltage be the same no matter how we choose the path joining the terminals.
In the case of magnetic components, we know that voltage along the path joining two points depends on the path, when we can go from one side of the magnetic flux region to the other. This is a direct consequence of one of Maxwell's equations (Faraday's law: curl E = -dB/dt) and basic vector integral calculus (Stokes theorem, the definitions of circulation and the definition of flux).
In order for voltage to be well defined, we must avoid paths that go through or 'on the other side' of the variable magnetic flux. The reason is simple: if the same starting and ending points admit two paths that are on opposite sides of the magnetic region, then the closed path formed by joining these two paths will enclose a variable flux and they must necessarily sum up to a nonzero value
Fig. two paths and the area enclosed (to be added later)
Now we know how to make voltage unique: allow only paths that cannot get into the forbidden zone. We enclose the component inside a black box (or an impenetrable wall) and we do not question what is inside. We must also ensure that our circuit path - the orange dashed line - does not contain variable magnetic flux itself.
Here is a lumpable circuit. The same circuit can be considered
- lumpED, when we avoid the forbidden paths by erecting an impenetrable wall and we only access the magnetic component through its terminals (note the circuit path that does not go into the forbidden zone, but instead jumps at the terminals). KVL works inside the green circuit path.
- NOT lumped, when we consider a circuit path (for the same physical system that we usually address with the name 'circuit') that encloses part or all of the variable magnetic flux region. In this case any path inside the orange dashed line that represent the circuit's premises is allowed. Some of these paths - not all, but only one would suffice - can 'go on the other side' of the magnetic region, making voltage between two points NOT WELL DEFINED.
(https://i.postimg.cc/8kFQxNqc/Lumpable-can-be-lumped-or-not.jpg)
Fig. the same lumpable circuit can be considered either lumped or not lumped
https://i.postimg.cc/8kFQxNqc/Lumpable-can-be-lumped-or-not.jpg
So far, so good: it looks like we have freedom to choose when we can make KVL works.
NO. There are circuits that are not lumpABLE. There are circuits where the circuit path is REQUIRED by definition or physical constraint to include the variable flux region. In this case it is not possible to find a green circuit path that connects the lumped components AND does not contain the variable flux region at its interior. Only orange paths are available.
Lewin's ring is an example of such a circuit. The resistors R1 and R2 are required to be on the opposite sides of the solenoid, i.e. the variable flux region. And you cannot find a circuit path that connects them without enclosing such forbidden zone. Voltages for points on your circuit will be path dependent.
(https://i.postimg.cc/5NyZDPVS/Unlumpable-circuit.jpg)
Fig. an unlumpable circuit: you cannot exclude dB/dt region from the circuit path
https://i.postimg.cc/5NyZDPVS/Unlumpable-circuit.jpg
And, no. You cannot model it with several tiny little transformer secondaries distributed along the perimeter, because you would forfeit the constraint that the two resistors be on the opposite sides of the variable magnetic region. It's exactly that constrain - your circuit path containing the dB/dt region - that makes Lewin's ring so special.
If you change the magnetic field region you are considering a different problem
(https://i.postimg.cc/x1KgZHcP/Spot-the-differences.png)
Fig. an unlumpable circuit: you cannot exclude dB/dt region from the circuit path
https://i.postimg.cc/x1KgZHcP/Spot-the-differences.png
In order to model it with two or four lumped coils, the magnetic field region must be split to accommodate a circuit path that does not include any of it. I used the same 'stellated' path style used by Feynman in figure 22-9 on page 22-7 of his second volume of lectures.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
If both your theory and experiments depend on each other, that'll do you no good.
Because the experimental data presented here was obtained by more or less blindly poking around circuits with a volt meter, and without any understanding of what is actually going on. So the measurements taken do not support in any form the claim that "KVL holds".
Talk for yourself! Don't reflect your ignorance into other people. When I saw Lewin's experiment for the first time I thought immediately: he is ignoring the induced voltage in the scope probes! The other day I showed Lewin's circuit to a friend of mine and almost instantaneously he also said "he is measuring the voltages incorrectly". I bet that is the case with the vast majority of people that know how to use an oscilloscope.
As for "If both your theory and experiments depend on each other, that'll do you no good", well, last time I checked that is how science works. That is exactly how Maxwell equations were derived.
It's not possible to measure two different voltages in the same spot.
Why does the wall have to be there? How about I put my wall here, in the very center of the toroid just to keep idiots from dropping their volt meter leads through there, as shown in the diagram below - it's functionally identical to your wall, yes? And its a lot less bricks!
(https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg (https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
Above: See the crosshatched wall inside of the core.
Actually, your ring above is COMPLETELY lumpable as a 1 turn transformer output in series with two resistors.
I am not even sure this sentence makes any sense. But I will post the fields for your clock, and you will see that what you are measuring is the path integral of the conservative part of the electric field along the hands of the clock. So much for your good probing...
Just like shown with my Lewin Clock, there are planes along which probe leads may be run where there is no non-conservative field which allows unambiguous physical measurements to be made of the two half-turns.
No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
It really is their religion, isn't it? I hate to say it, but that seems to be what it comes down to.
Not by my calculations!No, it all boils down to certain people being unable to understand what they read, and being incapable of assimilating new concepts that go beyond their limited knowledge. Like trying to explain the orbit of planets with epicycloids: it works numerically, but it betrays a fundamental ignorance of the actual physical phenomena behind the motion.
Do you really think that by now these guys haven't already figured out that their rhetoric is pointless? They know darn well that Lewin is right, Mehdi is wrong, KVL doesn't hold under a varying magnetic field, static wires are just low ohm resistors that can't generate voltages, you can measure two different voltages across the same two points in a circuit, etc., etc., etc.
So, if they are not intellectually impaired, why do they keep producing assertions that deny the evidence and reject facts and logic? Even when repeatedly debunked left and right?
As I said in an early post, stupidity is a moral issue. Even when you give them the answer they expect, they'll say you're wrong. This is because they determined arbitrarily that you're wrong. No matter what.
Although discussing with them may sometimes produce an interesting socratic-like dialog, it also may give the occasional reader the impression that their questioning is legitimate.
You have nothing else but to resort to the "Moral High Ground Fallacy". On the other hand, the KVL side has provided theoretical results and experimental results that perfectly agree with each other. What have you provide? Just a big pile of steaming BS.
It really is their religion, isn't it? I hate to say it, but that seems to be what it comes down to.
Yet the only thing you managed to prove is that Lewin is right and you are wrong.
Keep on trying.Thank you!
Who knows you manage to win converts to the cause of stubborn ignorance.You realize of course both sides feel the same way about the other side, right?
Why does the wall have to be there? How about I put my wall here, in the very center of the toroid just to keep idiots from dropping their volt meter leads through there, as shown in the diagram below - it's functionally identical to your wall, yes? And its a lot less bricks!
(https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg (https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
Above: See the crosshatched wall inside of the core.
Good, it seems that the top right corner of this image I posted nearly a week ago
(https://i.postimg.cc/R04QGyHs/KVL-works-if-I-leave-out-the-magnetic-region.jpg)
has finally reached your brain. A little slow, but better late than never.
Of course, you still don't understand it even though I remade both images using the very same circuit. Voltage is path-dependent in both situations: with or without a wall.
What we choose to do in order to be able to apply KVL in our circuit is limit our circuit path to the region of space where voltage between any two points is the same for all paths within that region of space. In short, we PRETEND voltage is single-valued because we willingly ignore the paths along which it will give multiple values.
The bag of nails in my basement is nodding. It seems to be able to understand this.
Do you?
QuoteActually, your ring above is COMPLETELY lumpable as a 1 turn transformer output in series with two resistors.
Prove it.
QuoteActually, your ring above is COMPLETELY lumpable as a 1 turn transformer output in series with two resistors.
Prove it.
Draw the resistors in that exact position around the shaded dB/dt region, with that shape and size (the one where I write "Example where there is no room to twist it"), and then draw a green dashed line that is your circuit's path. It has to join the resistors' terminals with one another and with the lumped transformer. Note that the shaded disk should all be contained into your lumped transformer, and your green dashed circuit path must NOT INCLUDE the shaded disk.
Go ahead, I'll wait for your picture.
QuoteI am not even sure this sentence makes any sense. But I will post the fields for your clock, and you will see that what you are measuring is the path integral of the conservative part of the electric field along the hands of the clock. So much for your good probing...
Just like shown with my Lewin Clock, there are planes along which probe leads may be run where there is no non-conservative field which allows unambiguous physical measurements to be made of the two half-turns.
But let's put this aside for a while, you will comment when I have posted the pictures.
For the moment, let's see that picture where you lump Lewin's rings by enclosing the shaded disk inside your transformer but NOT inside the circuit path that connects it to the resistors.
Remember, the resistor and the disk must remain in the same position, you cannot move them nor split it.
I am waiting.
About the "experiments". It should be abundantly clear by now what is wrong with Jesses EI-core measurements and why they are no proof for "KVL holds". What more than "the solution is in the fields" (plural) can I say.
One cannot consider only the magnetic flux and simply ignore the electric field that is inevitably present as well.
[...]
It's not possible to measure two different voltages in the same spot.
But you aren't measuring the voltages in the same spot, are you? The two voltmeters are in two different spots.
Why does the wall have to be there? How about I put my wall here, in the very center of the toroid just to keep idiots from dropping their volt meter leads through there, as shown in the diagram below - it's functionally identical to your wall, yes? And its a lot less bricks!
(https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg (https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
Above: See the crosshatched wall inside of the core.
The real answer is "Don't add undocumented turns to your transformer and expect physics to work."
Your probing method inherently subtracts induced voltage from your reading, leaving you with only the ohmic losses.
[...]
You are, buy definition, only measuring ohmic losses, because you are using a method of measuring which specifically subtracts all induced voltage differences.
QuoteNow the big question is of course, can KVL be somehow made to work in this arrangement, and for that we need to find an equivalent circuit with lumped elements. That will prove to be difficult, because one cannot find a place where to stick a lumped transformer winding or voltage source and still satisfy all the measurements taken in the various places. We can obviously not put it in the wires between the resistors, because we measure 0V across them. It can also not be in "R" and/or in "2R". If we put a 2/3V source "inside" 2R, that would violate the "-1/3V" reading on the rightmost volt meter.
So, where is it? Apparently it is there, but we cannot pinpoint it and measurements between two identical points show different results depending on how we instrument the circuit (1/3V, 2/3V, -1/3V). For circuit theory and KVL this is a nightmare. That's why there are "equivalent circuits" e.g. for transformers which try to model physics with lumped elements full of imaginary numbers and "magic items" like ideal transformers because they relieve engineers of having to think about physics. And to make KVL work. But now and then, when Sir James Clerk Maxwell makes an appearance, everyone is baffled why their circuits don't work.
The only reason we cannot pinpoint it is because it is all the way around. Sure, it MODELS and MEASURES as if it's at the center, but if you look at Faraday, and Maxwell, it's dB/dt inside an area, and measuring it on a solid core of effective infinite length is difficult because the active element of the transformer is no different than our volt meter leads, and they too, suffer from that same effect of induced voltage.
And then we end up with this crazyness where you claim there is 0 volts across all the wires, but 1 volt across the resistors, where exactly is the voltage coming from?
Oh? It's induced? So it is there. It's just difficult to measure in certain specific situations which have been designed for it to be difficult to measure.
[...]
Sorry man, it's all been explained and shown in pictures and equations. But you just ignore them.
Instead you make up incomplete analogies, like the "wall inside the transformer".
Go back and look at the diagram I made about the ring core transformer. It's all there in red, blue and green. If you don't understand how this transfers to your EI core, sorry, not going to spoonfeed you.
The electric field is there. It cannot be ignored. It cannot be discussed away if you don't want to neglect everything discovered in physics since 1861.
Why does the wall have to be there? How about I put my wall here, in the very center of the toroid just to keep idiots from dropping their volt meter leads through there, as shown in the diagram below - it's functionally identical to your wall, yes? And its a lot less bricks!
(https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg (https://i.postimg.cc/qqG0vgRV/20211124-213839.jpg)
Above: See the crosshatched wall inside of the core.
The real answer is "Don't add undocumented turns to your transformer and expect physics to work."
This "wall inside the transformer" is not equivalent.
It makes people believe they'll be safe if their probe leads do not cross it and so they stop looking at the complete paths and instead concentrate on "forbidden planes". It has certainly not stopped you from adding "undocumented turns" in your EI core experiment.
Your probing method inherently subtracts induced voltage from your reading, leaving you with only the ohmic losses.
[...]
You are, buy definition, only measuring ohmic losses, because you are using a method of measuring which specifically subtracts all induced voltage differences.
But there's no choice, really.Your voltmeter will only show you the sum of the electric fields along the path formed by its probe leads and whatever is between the tips.
This path can either be conservative ("blue") or non-conservative ("red"). But you must treat each path as independent from all other paths. For example in my diagram, the RED path containing the rightmost voltmeter only sums up fields along its path, i.o.w the electric field across "2R" and all external electric field components around the core (green arrows) it encloses! It doesn't matter if the probe leads penetrate your "wall inside the transformer" because "2R" is also on that path, closing the loop. Do you still not see what happened with your EI core?
Wrong.QuoteNow the big question is of course, can KVL be somehow made to work in this arrangement, and for that we need to find an equivalent circuit with lumped elements. That will prove to be difficult, because one cannot find a place where to stick a lumped transformer winding or voltage source and still satisfy all the measurements taken in the various places. We can obviously not put it in the wires between the resistors, because we measure 0V across them. It can also not be in "R" and/or in "2R". If we put a 2/3V source "inside" 2R, that would violate the "-1/3V" reading on the rightmost volt meter.
So, where is it? Apparently it is there, but we cannot pinpoint it and measurements between two identical points show different results depending on how we instrument the circuit (1/3V, 2/3V, -1/3V). For circuit theory and KVL this is a nightmare. That's why there are "equivalent circuits" e.g. for transformers which try to model physics with lumped elements full of imaginary numbers and "magic items" like ideal transformers because they relieve engineers of having to think about physics. And to make KVL work. But now and then, when Sir James Clerk Maxwell makes an appearance, everyone is baffled why their circuits don't work.
The only reason we cannot pinpoint it is because it is all the way around. Sure, it MODELS and MEASURES as if it's at the center, but if you look at Faraday, and Maxwell, it's dB/dt inside an area, and measuring it on a solid core of effective infinite length is difficult because the active element of the transformer is no different than our volt meter leads, and they too, suffer from that same effect of induced voltage.
Now wait a second. "We cannot pinpoint it because it is all the way around" does not rhyme with treating the red wires in your EI core experiment as lumped voltage sources, right?
Because there you claim (incorrectly) that, since your volt meter leads don't "go through the core" they don't have any voltage induced, right?NOOOOO! I am claiming that they MODEL AND MEASURE as if they have no voltage induced when they don't go through the core. There is no non-conservative field OUTSIDE an (ideal) toroidal transformer core.
So the only voltage source must be the red wire, right? So which way will you have it? It cannot be both.How can you not see that I'm talking about HOW IT MODELS AND MEASURES?
QuoteAnd then we end up with this crazyness where you claim there is 0 volts across all the wires, but 1 volt across the resistors, where exactly is the voltage coming from?
Oh? It's induced? So it is there. It's just difficult to measure in certain specific situations which have been designed for it to be difficult to measure.
So what you're saying is that Nature is treating poor engineers badly and making it difficult for them on purpose. Bad, bad Nature! I shall put you on my naughty list! No presents for you this Christmas!
SCNR :-DD
PS: the induced potential is not difficult to measure. Just sum up all electric fields along the "R+2R" loop and there you have it: 1V. Just be careful not to accidentally add another non-conservative external electric field to your measurements and forget to account for it.
Sadly, my understanding hasn't changed.
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...
...
Dude, the reason your script looks like it stinks to you is because it stinks!
The Maxwell–Faraday version of Faraday's law of induction describes how a time varying magnetic field creates ("induces") an electric field
Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.
Sadly, my understanding hasn't changed.
...
...
...
Dude, the reason your script looks like it stinks to you is because it stinks!
Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminals to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
Too bad my armchair is at the quantum mechanic's shop for repairs and I cannot fly away to another galaxy.
Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.Says the guy that when solving Lewin's ring, the first thing he does is to lump the EMF, and then he follows up by using KVL to find the voltages in the resistors!
No, says the guy who uses Faraday's law and not KVL, but you can't tell the difference.Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.Says the guy that when solving Lewin's ring, the first thing he does is to lump the EMF, and then he follows up by using KVL to find the voltages in the resistors!
It seems you're way behind on answering questions -- all you do is ask ask ask ask, but you never answer in the last few days. It's about time you warmed up your crystal ball to get some answers!
Here's some questions I've been asking for days and you're refusing to answer:
You have admitted that in the V1 and V2 voltages in the diagram directly below will both read the same voltage, and you have also admitted that V2 will be suitable as an element in a KVL loop:
Question One:
How can V1 not also be suitable since they both measure the same voltage? Your own trusted source says that if an unambiguous physical measurement of the voltage across the two terminals can be obtained, then KVL holds! How can V1 not work for KVL?
Question Two:
Considering your own trusted source, if a ONE TURN TRANSFORMER SECONDARY on a toroidal transformer has a voltage that is unambiguously physically measurable, then it should qualify as an element for a KVL loop, Correct?
For example, in the following transformer diagram with a safety wall in the center, why would the output winding not be suitable as an element in a KVL loop?
Oh boy, where to even begin...
Okay, first of all: I'm not in denial of observable reality. In fact, I took the reality YOU observed, turned it into a nice, colorful diagram and explained each measurement YOU did using only Ohm, Maxwell and Faraday. I showed in which loops voltage is induced and why not in others, explained every number you obtained.
Here it is again:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1331327)
Second: I did not "dream up" any "magic electric field". It's existence was found and explained by James Maxwell. It's his second field equation.Ahhh, you have to add in a secondary winding measure this electric field you talk about extending to infinity. Why'd I have to ask 3 times to get an answer?Quote from: WikipediaThe Maxwell–Faraday version of Faraday's law of induction describes how a time varying magnetic field creates ("induces") an electric field
Third: It is very obvious how to measure it: create a wire loop around any area with changing magnetic flux, create some discontinuity (make a cut, put a resistor in the loop), measure the electric field across it. The probe is just some wire coiled up. It senses non-conservative electric fields. Just the same, each turn around a transformer core "measures" this electric field.
I hope this is not too much to stomach.
You mentioned repeatedly how the magnetic flux is fully contained inside a transformers core (which is not exact but, eh, good enough). Then explain how a conductor (charge particles) outside of the core and thus outside of the magnetic flux, can interact with it. "Spooky action at a distance"? The answer "Dude, because Faraday" is not enough. What is the mechanism behind it?
Btw how's that lumped circuit coming along @Sredni asked you to come up with?
If you honestly answer the above questions and I'll do my best to draw up Lewin's loop and show how I would measure the voltage across the half turns.
It seems you're way behind on answering questions -- all you do is ask ask ask ask, but you never answer in the last few days. It's about time you warmed up your crystal ball to get some answers!
Here's some questions I've been asking for days and you're refusing to answer:
No, I have answered the questions that made some sense. But you have such big holes in your knowledge that you end up asking questions that have little to no sense. I was going to make a post about the misconceptions your posts are full of, but there are way too many. For example, I have written many many times that KVL applies in all regions of space that do not contain/cut a variable magnetic flux. So, in the lumpable circuit with the twisted wire it goes without saying that, since there is no changing flux in the small loop formed by V2, the wires and the jump at the first twist, KVL works.
But you keep asking questions that contain nonsense in themQuoteYou have admitted that in the V1 and V2 voltages in the diagram directly below will both read the same voltage, and you have also admitted that V2 will be suitable as an element in a KVL loop:
What the heck does "V2 (or V1) is suitable as an element in a KVL loop"???
V2 is a voltmeter, to begin with, but ....
... let's consider it a branch. A branch alone can be part of a loop to which KVL applies (works) and AT THE SAME TIME be part of a loop to which KVL does NOT apply.
Case in point: Lewin's ring with the two 'external' voltmeters. V1 forms a loop with R1 that you can apply KVL to, but forms with R2 (and V2) loop(s) to which you cannot apply KVL to, you need Faraday.
Therefore:QuoteQuestion One:
How can V1 not also be suitable since they both measure the same voltage? Your own trusted source says that if an unambiguous physical measurement of the voltage across the two terminals can be obtained, then KVL holds! How can V1 not work for KVL?
This question betray your confusion. I cannot answer this question because you are showing not to possess the prerequisite to formulate a rational question. V2 in the twisted circuit can be though as part of a circuit that stops at the first twist.
If you limit yourself to paths that are inside that little loop, V2 will always be part of loops to which KVL can be applied (because in the universe that is the area enclosed by your circuit path there is no dB/dt).
Yes, you can define your circuit path to follow all the twists and go around the core, but that betrays your ignorance of the purpose of making the transformer's terminal so close together: it's to treat the circuit with V2 as lumpED.
V1, on the other hand, is part of a circuit whose circuit path you can immediately see going around the core. Anyway, being a lumpABLE circuit you can choose both ways. If you choose the copper as the trail of your circuit path, you include the dB/dt region inside it. There are paths that when part of a loop along with V1 will go around the core, hence KVL will not apply. Faraday's will.
QuoteQuestion Two:
Considering your own trusted source, if a ONE TURN TRANSFORMER SECONDARY on a toroidal transformer has a voltage that is unambiguously physically measurable, then it should qualify as an element for a KVL loop, Correct?
For example, in the following transformer diagram with a safety wall in the center, why would the output winding not be suitable as an element in a KVL loop?
Again, the question betrays your ignorance. That is a lumpABLE circuit. You can treat it either as NOT LUMPED, by allowing paths that go around the core by considering an orange circuit path that follows the conductor around the core, or lumpED by denying this possibility by considering a green circuit path that jumps at the terminals, excluding this possibility. The wall is just a way to represent the fact that you are denying this possibility and your circuit path skips the innards of the transformer.
If you deny this possibility, then your voltages will be well defined (as Desoer and Kuh require for KVL to hold).
If you allow this possiblity, then your voltage can be multivalued (and Desoer Kuh will say that KVL ceases to work for those loops with a part 'going the other side').
(To tell it all, we should make the terminals close together so that the circuit itself can be shrinked to a point, but I decided not to push this. )
The key property associated with lumped elements is their small size
(compared to the wavelength corresponding to their normal frequency of operation.)
From the more general electromagnetic field point of view, lumped elements
are point singularities; that is, they have negligible physical dimensions.
You realize of course both sides feel the same way about the other side, right?
You realize of course both sides feel the same way about the other side, right?
There are no sides here.
That KVL doesn't hold under varying magnetic fields is an established fact, experimentally confirmed and predicted by the theory. We are not siding with Lewin or anyone or anything.
No, says the guy who uses Faraday's law and not KVL, but you can't tell the difference.Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.Says the guy that when solving Lewin's ring, the first thing he does is to lump the EMF, and then he follows up by using KVL to find the voltages in the resistors!
A rose by any other name is still a rose! You are the one that can not tell they are the same...
No, says the guy who uses Faraday's law and not KVL, but you can't tell the difference.Oh, goodness me. What a wondrous, copious and melliflously superfluous word salad. All to hide the fact that you cannot lump Lewin's ring. Here, let me repeat the question you are so eloquently avoiding to answer.Says the guy that when solving Lewin's ring, the first thing he does is to lump the EMF, and then he follows up by using KVL to find the voltages in the resistors!
A rose by any other name is still a rose! You are the one that can not tell they are the same...
You see Sredni? They understand that their claim that KVL, the real KVL, always holds is false. Haven't I told you? But to save face they're now calling Faraday's law KVL.
-- 2+2 = 5.
-- No, two plus two equals four.
-- Yeah, that's what I wrote.
-- No you wrote two plus two equals five.
-- No, I didn't.
-- Yes, you did. How to you call this number: 5?
-- Four.
I have a simple challenge for team 'Lewin'.
I have a simple challenge for team 'Lewin'.
It's not team 'Lewin'. It's team 'Classical Electrodynamics'.
But what's the point of the exercise?
Both 'teams' are doomed to find the same values for what is read by the voltmeters.
Anyway, if I copied it correctly - and there is no guarantee I did with all those turns making me dizzy - I would say
Vr1 = -24mV, Vr2 = +216mV
Vm1 = -136 mV, Vm2 = -56 mV
Provided I counted the 'rings' right and didn't change some sign here and there.
And if I got one sign wrong somewhere, that would proof that there can be say 200 mV in two inches of copper wire that carry a current of 100 nA?
Excellent! You got the correct results. Now, what is the voltage between nodes A and D, VAD?
Excellent! You got the correct results. Now, what is the voltage between nodes A and D, VAD?
I didn't find a way to make it glow, but let's see...
IT DEPENDS ON THE PATH.
The only established fact so far is that bsfeechannel has no idea of what he is talking about!!!
The only established fact so far is that bsfeechannel has no idea of what he is talking about!!!
C'mon, man! There's no shame in being wrong. You can bet your bottom dollar that all of us held at some time in the history of our lives the same misconceptions you and Jesse Gordon are now expressing. We normally get aware of voltages when we poke circuits with the probes of our meters and we have this intuitive, but misleading, perception that voltages are generated by the components. What components do is to shape the conditions in which the electromagnetic field exists in that region of the space. Voltages are the consequence of the existence of the fields. Once you switch your "paradigm" to think in terms of fields--not just circuits--you immediately expand the capabilities of your analyses.
For some of us, the shift is very difficult. But it is worth it.
If you honestly answer the above questions and I'll do my best to draw up Lewin's loop and show how I would measure the voltage across the half turns.
Oh, no. Now you answer MY question, not a question of your choice.
And my question is:
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg)
https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminals to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
You realize of course both sides feel the same way about the other side, right?
There are no sides here.
That KVL doesn't hold under varying magnetic fields is an established fact, experimentally confirmed and predicted by the theory. We are not siding with Lewin or anyone or anything.
Oh boy, where to even begin...
Okay, first of all: I'm not in denial of observable reality.
No it doesn't depend on the path, because we are calculating it.Excellent! You got the correct results. Now, what is the voltage between nodes A and D, VAD?
I didn't find a way to make it glow, but let's see...
IT DEPENDS ON THE PATH.
OK here's how anybody can unambiguously physically measure the induced voltage in half of an air-core transformer secondary turnIf you honestly answer the above questions and I'll do my best to draw up Lewin's loop and show how I would measure the voltage across the half turns.
Oh, no. Now you answer MY question, not a question of your choice.
And my question is:
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminals to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
Sure, now use your vast knowledge of electromagnetic fields and help Sredni calculate the voltage VAD from the problem above.
It's like trying to explain color to someone who is blind since birth.
I have already calculated "VAD" twice: its value depends on the path.
On the path set by the first voltmeter I get -136mV; on the path set by the second voltmeter I get -56mV.
I can compute on any path I want, if I know how the dB/dt region is partitioned by the path itself. Do you have any idea how easy it is for me to compute it? The only difficulty is making sure I am following that spiral labyrinth you set up hoping to get us confused.
Now, I solved your challenge.
Will you solve a few very elementary problems I pose? Or will you evade my questions as Jesse Gordon is doing?
Sure, now use your vast knowledge of electromagnetic fields and help Sredni calculate the voltage VAD from the problem above.
My "vast knowledge" won't help you. I asked the same questions long ago, got the right answers, but ended up like you: confused.
I can show you the door to your enlightenment, but I can't walk you through it. You'll have to do it yourself.
It's like trying to explain color to someone who is blind since birth.
I have already calculated "VAD" twice: its value depends on the path.
On the path set by the first voltmeter I get -136mV; on the path set by the second voltmeter I get -56mV.
I can compute on any path I want, if I know how the dB/dt region is partitioned by the path itself. Do you have any idea how easy it is for me to compute it? The only difficulty is making sure I am following that spiral labyrinth you set up hoping to get us confused.
Now, I solved your challenge.
Will you solve a few very elementary problems I pose? Or will you evade my questions as Jesse Gordon is doing?
You have solve nothing!
---snip---
This is the challenge: Calculate V1, V2, Vx, and Vy.
Excellent! You got the correct results.
It's like trying to explain color to someone who is blind since birth.
I have already calculated "VAD" twice: its value depends on the path.
On the path set by the first voltmeter I get -136mV; on the path set by the second voltmeter I get -56mV.
I can compute on any path I want, if I know how the dB/dt region is partitioned by the path itself. Do you have any idea how easy it is for me to compute it? The only difficulty is making sure I am following that spiral labyrinth you set up hoping to get us confused.
Now, I solved your challenge.
Will you solve a few very elementary problems I pose? Or will you evade my questions as Jesse Gordon is doing?
You have solve nothing!
---snip---
It's a no, then?
You confirm will evade questions just like Jesse has done till now?
By the way: your challenge wasQuoteThis is the challenge: Calculate V1, V2, Vx, and Vy.
I calculated them (it took me some six-seven minutes, mostly to decide to get off the couch and find paper and pencil, and to make sure I had copied the spirals right), and you said it yourself:QuoteExcellent! You got the correct results.
And now you are on your victory lap as if you were the only one to get the correct results. (And all this after I wrote, in the same message I posted the solution in: "Both 'teams' are doomed to find the same values for what is read by the voltmeters."
Go figure.
I wonder if 'everyone else reading' should be made aware that your solution forecasts that a copper wire a few inches long will drop 20 mV when a current of 0.24 mA flows through it. But hey, you have tiny little batteries in your wires, right? Like they explained coils in high school.
So, to be clear, you won't try to solve the simple circuit quizzes I pose?
You must be the kind of guy than never pays up when he loses a bet.
Once again, what is the value of VAD?
Once again, what is the value of VAD?
Once again:
It depends on the path.
How did place the probes to measure it? Midway through the disk, because you chose an highly symmetrical setup?
How would you place the probes in the solenoid was made in triangular shape and the ring with the resistor shaped as Mickey Mouse's head silhouette, tilted and off-center?
You must be the kind of guy than never pays up when he loses a bet.
Once again, what is the value of VAD? Go argue with results:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3842183/#msg3842183 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3842183/#msg3842183)
And I am repeating you, in size 18pt, 24pt, 36pt, that it depends on the path. So, in order for me to calculate it, I need to know the path (actually it suffice to know how it partition the flux region). Because voltage is a path integral and in the presence of variable magnetic field, per Maxwell equations, it does depend on the path. I know you don't like it and you want to consider the scalar electric potential difference, instead, but if we use different definitions, you have to accept we have to use different methods.Nope, the voltage VAD is ALWAYS -96mV. I asked you to calculate it, not to measure it.Once again, what is the value of VAD?Once again:
It depends on the path.
How did place the probes to measure it? Midway through the disk, because you chose an highly symmetrical setup?
How would you place the probes in the solenoid was made in triangular shape and the ring with the resistor shaped as Mickey Mouse's head silhouette, tilted and off-center?
For this particular configuration of the problem, it is fairly easy to setup the probe so that the external magnetic field does not induce a voltage on it. The calculation perfectly matches the measurement.
When Lewin did his experiment with a similar shape, he did not extract the correct equivalent circuit, and then he couldn't figure out what VAD was, so he blamed KVL.
2) wenn die Drahte 1, 2, n, eine geschlossene Figur bilden
R1 I1 + R2 I2 + ... + Rn In
= der Summe aller elektromotorischen krafte, die sich auf dem Wege: 1, 2, n befinden; wo R1, R2, Rn die Widerstande der Drahte, I1 I2,... die Intensitaten der Strome bezeichnen, von denen diese durchflossen werden, alle nach einer Richtung als positiv gerechnet.
2) if the wires 1, 2, n, form a closed figure
R1 I1 + R2 I2 + ... + Rn In =
= the sum of all electromotive forces located on the path: 1, 2, ...n;
where R1, R2, ... Rn are the resistances of the wires, and I1 I2, ...In denote the intensities of the currents that flow through them, all calculated as positive in one direction.
"It was shown by G Kirchhoff (1824-87) in 1849 that localised EMFs generally set up auxiliary electrostatic forces, by means of surface charges, in order to establish a uniform current around the circuit (Kirchhoff 1879 pp49-55, 1514). Since these additional fields are conservative, the sum of the net potential differences around the whole circuit will be exactly equal to the sum of the PDs across the localised underlying EMFs only. This is the substance of Kirchhoff’s second network law (Kirchhoff 1879 pp 15-16)"
... The KVL-Always-Holders ...
And here is something peculiar I noticed in ElectroBoom's video about KVL
Look at what he emphatically states is NOT 'his' definition of KVL (it genuinely pained me to see him put a big X through a time-invariant form of Maxwell's Equations),
https://youtu.be/d-a9Pr2z-qg?t=253 (https://youtu.be/d-a9Pr2z-qg?t=253)
Meanwhile, look at the Feynman Lectures he claimed in previous videos, supports his made up pseudoscientific definition, Section 22-3, Eq. 22.14
https://www.feynmanlectures.caltech.edu/II_22.html (https://www.feynmanlectures.caltech.edu/II_22.html)
Look at what the line integral of the E-field around a closed path is equal to: the sum of the voltages in the loop. When there are no time-varying magnetic fields, what does that sum equal to? Zero.
So, he's saying that the line integral of the E-field around a closed loop being zero is NOT his definition of KVL... but the line integral of the E-field around a closed loop IS the sum of the voltages around the loop... and if that line integral is zero and path independent, you have KVL.
So, uhh, what is he talking about? More made up science?
And this reminds me of something someone noted last time this came up in a big way. The KVL-Always-Holders have inconsistent explanations amongst one another for why these voltmeters connected to the same point read different values. But when one applies Faraday's Law, one of Maxwell's actual equations, there is no inconsistency in explanation and multiple types of phenomena are easy to explain and model and, yes, reduce to KVL-lumped expressions (as Feynman writes is possible under specific circumstances).
I am also interested in the mechanisms of rejection, cognitive dissonance, confirmation bias, and the like.
Unfortunately the only two KVLers left have lowered the level by several notches, by becoming obnoxiously repetitive...
(https://i.postimg.cc/2SfmvWFM/20211128-113309.jpg)If you honestly answer the above questions and I'll do my best to draw up Lewin's loop and show how I would measure the voltage across the half turns.
Oh, no. Now you answer MY question, not a question of your choice.
And my question is:
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg)
https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminals to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
OK here's how anybody can unambiguously physically measure the induced voltage in half of an air-core transformer secondary turn
Nice try, but you did not answer the question.
Let me repeat it for you here, in case you missed:
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg)
https://i.postimg.cc/kX0TSBw6/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminals to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
Please, please, please, do not fly to another galaxy with your armchair before answering it.
GOTO 500
"I don't know of any KVL-Always-Holders."
You're not terribly well acquainted with the debate then.
ElectroBoom (the guy who this thread is about)
literally, and rather triumphantly, declares that KVL holds in all cases, his words (with accompanying fanfare music):
https://youtu.be/Q9LuVBfwvzA?t=838
As for me, I'm not terribly interested in saving KVL or going around in infinite loops with you (which is why I wanted to say my thanks to Sredni and bsfeechannel for their seemingly inexhaustible patience). Besides, KVL is not one of Maxwell's Equations anyway. Faraday's Law is.
On the flipside, no one here is a Lewinite (kind of gross phrasing anyway,What would you call them? They call us "KVLer's" or "KVL-ALWAYS-HOLD"ers or whatever.
as if this is a 'battle of personalities'... but that's what ElectroBoom wanted when he titled his first video "Disagreeing with a Master").
We're just people who have studied Maxwell's Equations. They were around before Lewin was even born, other people have described them well, and they'll be here long after us.
I did show how anybody can unambiguously physically measure the voltage across a half-turn on Lewin's circuit.
Jesse, Jesse...
I did answer your question related to the previous circuit. I also pointed out that the answer was in the top right corner of my images for Lumped and Not lumped circuits. You seem to think that, because lumpABLE circuits exists and as such can be made lumpED by choosing a suitable circuit path, then there cannot be alternatives.
There are alternatives:
Alternative 1: the lumpABLE circuit itself. You choose another circuit path (for the same set of components and connecting wires!) that does include the variable magnetic region. Your system has now path dependent voltage and is NOT lumped.
Alternative 2: there are other circuits in the universe that are UNlumpable. Lewin's ring is one example.
And the fact that you cannot come up with an answer to my question is proof that you are not able to lump it. Don't feel bad. Nobody can lump that without incurring in self-contradiction. It's not your fault. It's the circuit that's drawn like that.
Now you try to shift the attention on yet another lumpABLE circuit, putting your voltmeters in a manner that imply you prefer to use a circuit path that makes it lumpED. Yes, as a lumpABLE circuit, it can be lumpED. But this does not imply that
1. it can also be seen as NOT lumped, by choosing a different circuit path (same components, same wires, same transformer!)
2. there are other circuits out there that are UNlumpable
I really cannot be more clear than this. Try some vitamins, maybe?
But here's the deal: if you put the numerical values of the voltages read by your voltmeters, I will show you the NOT lumped version of your circuit, so that you will avoid posting it again in the same way you are avoiding my question on how would you lump Lewin's ring.
Deal?
EDIT: grammar and clarification about what values I want you to fill in.
Time to sleep, perchance to die, for me.
brilliantly debunked by Lewin.
experimentally?
I did show how anybody can unambiguously physically measure the voltage across a half-turn on Lewin's circuit.
And a quarter turn or any fraction of a turn by that matter! The blockheads in team Lewin don't want to accept that.
The part of this debate I'm involved in has nothing in particular to do with Mehdi. We've been arguing for weeks here about whether KVL holds in Lewin's (and other simple) circuits, regardless of what Mehdi Said he.
Literally, yes, but not in context. If you watch the whole video, he's talking about a variety of different cases which he demonstrates - AND - he runs his cases by Dr. Belcher, who writes up a nice writeup about a bunch of Mehdi's experiments, and then concludes that "KVL holds as argued by Mehdi."
So the CONTEXT was that of all the different example circuits that Mehdi gave to Belcher, Belcher said that KVL holds for all of them. Which is what Dr. Belcher said.
And Dr. Belcher even quoted Dr. Feynman.
Neither Belcher nor Mehdi are saying that KVL holds for every possible circuit of every possible configuration, but rather that it holds for all the ones they've just examined.
By taking Mehdi's words out of context, you make him out to say something completely different than he was actually communicating.
Your strong negative bias shines like the sparks off Mehdi's fingertips, and smells like his burning clip leads.
And that's what I get far and wide. The people arguing for Lewin being right are dreadfully reluctant to actually show that they can do real physics. See how you side stepped my question?
They claim to know it all, but can demonstrate none of it, except they are sure about one thing, and that is Lewin was right.
What would you call them? They call us "KVLer's" or "KVL-ALWAYS-HOLD"ers or whatever.
I know that air core transformers existed long before Lewin, but I think Lewin was just who really made the party trick well known - the combination of his entertainer style and youtube publicity was what it took to spark it off.
Then they posted that textbook page which says that KVL holds if the voltage across the terminals can be unambiguously defined by physical measurements - and by George - we seem to be unambiguously defining the voltages by physical measurements, so I say it's time we all agreed that KVL holds for Lewin's circuit! :-DD
All the KVLer's are gone except two, and they are taken down about 12 notches, frantically just repeating themselves
Quote from: armandine2Yes. Try it yourself.Quote from: bsfeechannelbrilliantly debunked by Lewin.experimentally?
Lewin showed at least one circuit where KVL doesn't hold. Everyone repeated his experiment and obtained the same result. Conclusion: KVL does NOT ALWAYS hold. End of story.
He, and everyone who repeated the experiment, measured the voltages and they didn't add up to zero. That's how he showed it.
Then they posted that textbook page which says that KVL holds if the voltage across the terminals can be unambiguously defined by physical measurements - and by George - we seem to be unambiguously defining the voltages by physical measurements, so I say it's time we all agreed that KVL holds for Lewin's circuit! :-DD
Except the voltages are not unambiguous:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1331327)
Not in the circuit above (which is essentially the Lewin ring), not even in the EI core experiment that originally brought you here.
Above, the voltage across "2R" is either "-1/3V" or 2/3V, depending on the path your voltmeter probes are going. That's not what I call "unambiguous".
I don't quite know what you're getting at, because I see only single-turn windings, so, would you tell me where you see "transformer secondary" windings in the above diagram?Then they posted that textbook page which says that KVL holds if the voltage across the terminals can be unambiguously defined by physical measurements - and by George - we seem to be unambiguously defining the voltages by physical measurements, so I say it's time we all agreed that KVL holds for Lewin's circuit! :-DD
Except the voltages are not unambiguous:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1331327)
Not in the circuit above (which is essentially the Lewin ring), not even in the EI core experiment that originally brought you here.
Above, the voltage across "2R" is either "-1/3V" or 2/3V, depending on the path your voltmeter probes are going. That's not what I call "unambiguous".
AHHH THANK YOU! I've been asking for days what was ambiguous about my reading of the voltage on a toroidal transformer secondary!
The answer? If I don't know how many turns are on the winding, especially if they might change without me knowing it, then the reading is ambiguous.
For whatever its worth Sredni and bsfeechannel, I'm grateful for your efforts to continually educate about this topic even if it really seems like the KVLers are just running in circles through the madness inducing Lewin/Romer loop (puns somewhat intended).
The experiment is an excellent demonstration of the phenomena of non-conservative fields and path dependence. Lewin didn't come up with it nor did he really come up with the interpretations of the physics that describe it. Sredni has cited multiple well-respected authors and texts (it's in Feynman, Purcell, and Romer for starters). I'll add another into the mix: JD Kraus Electromagnetics, Chapters 4-10 and 8-2. Not that this makes an appeal to authority - just that it's not accurate to characterize Lewin's interpretation of KVL and Faraday's Law as the ramblings of a mad MIT scientist crackpot (as much as Lewin fits that stereotype with the wild hair and colorful clothes)... it's actually pretty mainstream in physics and applied EM textbooks.
The experiment is an excellent demonstration of the phenomena of non-conservative fields and path dependence. Lewin didn't come up with it nor did he really come up with the interpretations of the physics that describe it. Sredni has cited multiple well-respected authors and texts (it's in Feynman, Purcell, and Romer for starters). I'll add another into the mix: JD Kraus Electromagnetics, Chapters 4-10 and 8-2. Not that this makes an appeal to authority - just that it's not accurate to characterize Lewin's interpretation of KVL and Faraday's Law as the ramblings of a mad MIT scientist crackpot (as much as Lewin fits that stereotype with the wild hair and colorful clothes)... it's actually pretty mainstream in physics and applied EM textbooks.
The experiment is an excellent demonstration of Lewin having no idea of what he is talking about! Do you even understand what 'non-conservative fields' mean in this context? Have you realized that in the circuit, the one with the wire loop and the two resistors, all the energy induced due to the external varying magnetic field is equal to all the energy consumed by the resistors? That sounds pretty conservative to me!
Jesse, Jesse...But I'm asking a yes or no question, and you're saying everything other than yes or no.
I did answer your question related to the previous circuit. I also pointed out that the answer was in the top right corner of my images for Lumped and Not lumped circuits. You seem to think that, because lumpABLE circuits exists and as such can be made lumpED by choosing a suitable circuit path, then there cannot be alternatives.
There are alternatives:
Alternative 1: the lumpABLE circuit itself. You choose another circuit path (for the same set of components and connecting wires!) that does include the variable magnetic region. Your system has now path dependent voltage and is NOT lumped.
Alternative 2: there are other circuits in the universe that are UNlumpable. Lewin's ring is one example.
QuoteAnd the fact that you cannot come up with an answer to my question is proof that you are not able to lump it. Don't feel bad. Nobody can lump that without incurring in self-contradiction. It's not your fault. It's the circuit that's drawn like that.No, it means you're not explaining your question. You're asking me to draw something you're picturing in your mind. I did what I thought you wanted - I illustrated how to unambiguously physically measure the voltage across the half-turns in Lewin's experiment
QuoteMy question is a simple yes or no question. Either the volt meters will sum to zero or they won't. Or maybe you think they might some days depending on the phase of the moon.
Now you try to shift the attention on yet another lumpABLE circuit, putting your voltmeters in a manner that imply you prefer to use a circuit path that makes it lumpED. Yes, as a lumpABLE circuit, it can be lumpED. But this does not imply that
1. it can also be seen as NOT lumped, by choosing a different circuit path (same components, same wires, same transformer!)
2. there are other circuits out there that are UNlumpable
I really cannot be more clear than this. Try some vitamins, maybe?
QuoteBut here's the deal: if you put the numerical values of the voltages read by your voltmeters, I will show you the NOT lumped version of your circuit, so that you will avoid posting it again in the same way you are avoiding my question on how would you lump Lewin's ring.
I already showed you how I would lump Lewin's ring.
The experiment is an excellent demonstration of the phenomena of non-conservative fields and path dependence. Lewin didn't come up with it nor did he really come up with the interpretations of the physics that describe it. Sredni has cited multiple well-respected authors and texts (it's in Feynman, Purcell, and Romer for starters). I'll add another into the mix: JD Kraus Electromagnetics, Chapters 4-10 and 8-2. Not that this makes an appeal to authority - just that it's not accurate to characterize Lewin's interpretation of KVL and Faraday's Law as the ramblings of a mad MIT scientist crackpot (as much as Lewin fits that stereotype with the wild hair and colorful clothes)... it's actually pretty mainstream in physics and applied EM textbooks.
The experiment is an excellent demonstration of Lewin having no idea of what he is talking about! Do you even understand what 'non-conservative fields' mean in this context? Have you realized that in the circuit, the one with the wire loop and the two resistors, all the energy induced due to the external varying magnetic field is equal to all the energy consumed by the resistors? That sounds pretty conservative to me!
The experiment is an excellent demonstration of the phenomena of non-conservative fields and path dependence. Lewin didn't come up with it nor did he really come up with the interpretations of the physics that describe it. Sredni has cited multiple well-respected authors and texts (it's in Feynman, Purcell, and Romer for starters). I'll add another into the mix: JD Kraus Electromagnetics, Chapters 4-10 and 8-2. Not that this makes an appeal to authority - just that it's not accurate to characterize Lewin's interpretation of KVL and Faraday's Law as the ramblings of a mad MIT scientist crackpot (as much as Lewin fits that stereotype with the wild hair and colorful clothes)... it's actually pretty mainstream in physics and applied EM textbooks.
The experiment is an excellent demonstration of Lewin having no idea of what he is talking about! Do you even understand what 'non-conservative fields' mean in this context? Have you realized that in the circuit, the one with the wire loop and the two resistors, all the energy induced due to the external varying magnetic field is equal to all the energy consumed by the resistors? That sounds pretty conservative to me!
Oh dear...
https://farside.ph.utexas.edu/teaching/301/lectures/node59.html (https://farside.ph.utexas.edu/teaching/301/lectures/node59.html)
Path dependence of the line integral to do work is the defining characteristic of a non-conservative field.
https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/8-2-conservative-and-non-conservative-forces/ (https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/8-2-conservative-and-non-conservative-forces/)
We're not even talking about basic electromagnetics anymore (this is in Kraus Chapter 4). Sredni is right - the notches have been lowered back to basic Newtonian mechanics.
Another Lewin stooge apparently (the casual nature of his murdering of Kirchoff is astounding):
http://www.physicsbootcamp.org/Nonconservative-Electric-Field.html (http://www.physicsbootcamp.org/Nonconservative-Electric-Field.html)
Amazing.
The experiment is an excellent demonstration of the phenomena of non-conservative fields and path dependence. Lewin didn't come up with it nor did he really come up with the interpretations of the physics that describe it. Sredni has cited multiple well-respected authors and texts (it's in Feynman, Purcell, and Romer for starters). I'll add another into the mix: JD Kraus Electromagnetics, Chapters 4-10 and 8-2. Not that this makes an appeal to authority - just that it's not accurate to characterize Lewin's interpretation of KVL and Faraday's Law as the ramblings of a mad MIT scientist crackpot (as much as Lewin fits that stereotype with the wild hair and colorful clothes)... it's actually pretty mainstream in physics and applied EM textbooks.
The experiment is an excellent demonstration of Lewin having no idea of what he is talking about! Do you even understand what 'non-conservative fields' mean in this context? Have you realized that in the circuit, the one with the wire loop and the two resistors, all the energy induced due to the external varying magnetic field is equal to all the energy consumed by the resistors? That sounds pretty conservative to me!
The very fact that there is energy available for the resistors to consume, in a closed loop, shows that the field must be non-conservative. Because in a conservative field, all paths going back to their origin end on the same potential and there is no energy available.
In anticipation of your next argument: it is not the magnetic field that is being talked about here. The non-conservative field is the electric field that results from the changing magnetic flux.
Think of it as a top-down 2D projection of a spiral staircase. The XY plane is the "geometric" plane in which your path lies, the Z axis is the electric potential. The path is closed in the XY projection, but start and end of it have different Z coordinates and each "turn" in the XY plane lifts your Z coordinate by "-dB/dt".
One thing I have noticed with youtubers is they do not allow coherence or logic to get in the way of their videos. And after they reached a certain number of subscribers they can hardly admit their errors.
At least Mehdi does not seem to try to defend its blunders in the comment section, like others do (sometimes to the point of banning critics).
I am waiting to see if Dave will correct at least the description of his giant errors in the "Electricity misconceptions" video, or if he will let his followers listen to that nonsense about the Poynting vector only pointing outwards at AC and that fantasy connection with the skin effect (why not the proximity effect, then?). And it seems that misquoting Feynman is the ultimate signature of quackery in the EE field.
I got a rather interesting comment once, in fact I've had more than once in various forms, but the comment was basically: how do we know you're RIGHT? How can we take your word for it? On, you know, all these things and all these topics? And, well, you know, it's a really good question, and the answer is you SHOULDN'T. You should never take anyone's word for it. Don't take anything i say on these blogs as gospel. Uh, you know, I've been in the industry for 20 years so, you know, I like to think I do know what I'm talking about mostly. But, you know, don't take my word for it. All my blogs, and all the things I talk about on here are designed to be food for thought. You're supposed to use your own engineering judgment and, you know, and go out and verify things. If you're, you know, if you're really interested in something, don't complain that i didn't explain it right or and you know i might have got it a bit wrong or something like that. Go out and investigate for yourself. That's what it's all about: food for thought.
I also get something out of this. A selection of guinea pigs to test for holes in my exposition, required refinement in language (lumpABLE, lumpED, NOT lumped, UNlumpable...), and a stimulus to deepen my knowledge.
For example, I have now a very clear idea about how give a definition of voltage straight from electrostatics (from my 'silent post'), I overcame my 'fear' of partial (even straight, as paradoxical as it may seems) turns, and if need be I feel confident I could operate a 1821 multiplier with embedded bismuth-copper thermocouple (given enough ice and boiling water).
I am also interested in the mechanisms of rejection, cognitive dissonance, confirmation bias, and the like.
Unfortunately the only two KVLers left have lowered the level by several notches, by becoming obnoxiously repetitive...
QuoteLiterally, yes, but not in context. If you watch the whole video, he's talking about a variety of different cases which he demonstrates - AND - he runs his cases by Dr. Belcher, who writes up a nice writeup about a bunch of Mehdi's experiments, and then concludes that "KVL holds as argued by Mehdi."
So the CONTEXT was that of all the different example circuits that Mehdi gave to Belcher, Belcher said that KVL holds for all of them. Which is what Dr. Belcher said.
And Dr. Belcher even quoted Dr. Feynman.
Srendi has been through your misattributions of Belcher's words.
I'm not going to rehash it with you because, again, you want people to chase you in infinite loops. He already said it.
Yes, context matters. Mehdi takes Feynman and Belcher out of context. Mehdi made his positions clear in the first and second videos he released about this. He thinks KVL holds in all cases - he's still saying that. He's wrong.QuoteNeither Belcher nor Mehdi are saying that KVL holds for every possible circuit of every possible configuration, but rather that it holds for all the ones they've just examined.
By taking Mehdi's words out of context, you make him out to say something completely different than he was actually communicating.
Belcher wouldn't say that because he is an actual physicist who understands Maxwell's Equations. Mehdi on the other hand... this is what he actually is arguing. This is the whole reason he picked a fight with Lewin in the first place.
https://youtu.be/0TTEFF0D8SA?t=51
So why the desperation to save it? Why is it so very important that KVL applies to the Lewin/Romer Ring? Well I don't know why. This is why Sredni is fascinated by the cognitive bias - why does everyone want to save KVL so badly?
I'm pretty amazed that just studying Faraday's Law and saying "KVL doesn't always hold" makes one a Lewin cultist. And I'm not even an anti-KVLer... just someone who recognizes the limitations of when you can use it, I guess?
I don't quite know what you're getting at, because I see only single-turn windings, so, would you tell me where you see "transformer secondary" windings in the above diagram?Then they posted that textbook page which says that KVL holds if the voltage across the terminals can be unambiguously defined by physical measurements - and by George - we seem to be unambiguously defining the voltages by physical measurements, so I say it's time we all agreed that KVL holds for Lewin's circuit! :-DD
Except the voltages are not unambiguous:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1331327)
Not in the circuit above (which is essentially the Lewin ring), not even in the EI core experiment that originally brought you here.
Above, the voltage across "2R" is either "-1/3V" or 2/3V, depending on the path your voltmeter probes are going. That's not what I call "unambiguous".
AHHH THANK YOU! I've been asking for days what was ambiguous about my reading of the voltage on a toroidal transformer secondary!
The answer? If I don't know how many turns are on the winding, especially if they might change without me knowing it, then the reading is ambiguous.
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)If you place your voltmeters all in the same simply connected region that does not include the variable dB/dt region, then yes of course KVL will work. It's written in the top right corner of the picture I have posted more then a week ago. You still have to understand that?
https://i.postimg.cc/jdJntBXT/20211128-121506.jpg (https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
My question is a simple yes or no question. Either the volt meters will sum to zero or they won't. Or maybe you think they might some days depending on the phase of the moon.
So far you only proved you can't.
WHERE are you seeing "transformer secondaries"? You're evading answering again.
What Mehdi actually says at that point you link above is "Dr. Lewin teaches in one of his courses that KVL doesn't hold true in some cases and I disagree with him."
From the CONTEXT of watching the whole video, it is clear that Mehdi is not claiming that KVL holds in all possible electrical typologies and frequencies, but rather he is specifically talking about certain cases that Lewin and he experimented with.
But yeah, if you want to quote mine, find videos of people who aren't even speaking their native language, I bet you can find slight ambiguities in their out-of-context words which you can present out of context to mean something else.
However, an electric field with a time-varying magnetic field is not a conservative field. And we use this every day to great practical effect: we intentionally put currents in a loop within time-varying magnetic fields, and use those to extract electrical energy from the time-varying magnetic field (i.e. in generators), or use it to turn electrical energy into magnetic fields (i.e. in motors).
Regardless, we usually encapsulate these electromagnetic effects into our Lumped Element Model, and go on assuming that the electric field actually is conservative.
Understandably, this can be confusing and disorienting to beginners. Ninty-nine percent of the time, it’s safe to just assume the electric field is conservative, but if you’re doing anything with changing or moving magnetic fields, you should make a little mental note to remember that it’s really not.
WHERE are you seeing "transformer secondaries"? You're evading answering again.
I edited that post to show the extra secondary in my diagram, also updated the text as well.
You're basically saying I can move my volt meter probes to measure AF instead of AB and get a different reading, therefore AB is ambiguous.
(https://i.postimg.cc/bNr4Wmwk/20211130-124903.jpg)
That's a really really weak argument, because you could just as well say that any reading is ambiguous because by moving the probes to another part of the circuit we get a different reading.
But if it's the best you got, polish it to shine as bright as you can.
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
Emphasis mine. (Sredni, are you seeing this?!)
Oh my goodness. You think that because energy is conserved that fields must also be conserved? This is just - I don't even know what to say. :-\
Oh dear oh dear oh dear:
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/ (https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/)
It's amazing that you heard me say "the Lewin circuit demonstrates path dependence of non-conservative fields" and INSTANTLY thought this must be about conservation of energy. They're... not the same. You think conserved fields and conserved energy are descriptions of the same thing? :(
So yea, I guess you should review Newtonian mechanics before we deal with things like circulating magnetic fields:
https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf (https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf)
But I don't even know why I'm linking things for you - you're clearly not opening and reading them.
And I read your post with the circuit - Sredni asked you questions about it that you never answered.
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
Emphasis mine. (Sredni, are you seeing this?!)
Oh my goodness. You think that because energy is conserved that fields must also be conserved? This is just - I don't even know what to say. :-\
Oh dear oh dear oh dear:
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/ (https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/)
It's amazing that you heard me say "the Lewin circuit demonstrates path dependence of non-conservative fields" and INSTANTLY thought this must be about conservation of energy. They're... not the same. You think conserved fields and conserved energy are descriptions of the same thing? :(
So yea, I guess you should review Newtonian mechanics before we deal with things like circulating magnetic fields:
https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf (https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf)
But I don't even know why I'm linking things for you - you're clearly not opening and reading them.
And I read your post with the circuit - Sredni asked you questions about it that you never answered.
Wow, you sound a lot like bsfeechannel. Your ignorance hurts! Three questions for you: 1) How many fields do we have in the loop circuit with two resistors? 2) What is the instantaneous power induced in the circuit by the external varying magnetic field? 3) What is the instantaneous power consumed by the circuit? The answers are three real numbers. Anything else you say is BS.
Don't ask Sredni for help, he is busy trying to calculate the voltage between nodes 'A' and 'D', VAD.
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
Emphasis mine. (Sredni, are you seeing this?!)
Oh my goodness. You think that because energy is conserved that fields must also be conserved? This is just - I don't even know what to say. :-\
Oh dear oh dear oh dear:
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/ (https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/)
It's amazing that you heard me say "the Lewin circuit demonstrates path dependence of non-conservative fields" and INSTANTLY thought this must be about conservation of energy. They're... not the same. You think conserved fields and conserved energy are descriptions of the same thing? :(
So yea, I guess you should review Newtonian mechanics before we deal with things like circulating magnetic fields:
https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf (https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf)
But I don't even know why I'm linking things for you - you're clearly not opening and reading them.
And I read your post with the circuit - Sredni asked you questions about it that you never answered.
Wow, you sound a lot like bsfeechannel. Your ignorance hurts! Three questions for you: 1) How many fields do we have in the loop circuit with two resistors? 2) What is the instantaneous power induced in the circuit by the external varying magnetic field? 3) What is the instantaneous power consumed by the circuit? The answers are three real numbers. Anything else you say is BS.
Don't ask Sredni for help, he is busy trying to calculate the voltage between nodes 'A' and 'D', VAD.
Ah you refuse to learn about energy conservation as opposed to field conservation. No wonder Faraday's Law seems like a big inscrutable mystery that only KVL can save you from.
Did you open any of those links? Have you opened anything I've linked? Have you read Kraus, chapter 4? Or chapter 10? It's easy to find online.
Let me guess, you're going to say...
"That's all BS!"
WHERE are you seeing "transformer secondaries"? You're evading answering again.
I edited that post to show the extra secondary in my diagram, also updated the text as well.
You're basically saying I can move my volt meter probes to measure AF instead of AB and get a different reading, therefore AB is ambiguous.
(https://i.postimg.cc/bNr4Wmwk/20211130-124903.jpg)
That's a really really weak argument, because you could just as well say that any reading is ambiguous because by moving the probes to another part of the circuit we get a different reading.
But if it's the best you got, polish it to shine as bright as you can.
Nope. Where in MY diagram do you see "transformer secondaries". Point them out, please.
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)If you place your voltmeters all in the same simply connected region that does not include the variable dB/dt region, then yes of course KVL will work. It's written in the top right corner of the picture I have posted more then a week ago. You still have to understand that?
https://i.postimg.cc/jdJntBXT/20211128-121506.jpg (https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
My question is a simple yes or no question. Either the volt meters will sum to zero or they won't. Or maybe you think they might some days depending on the phase of the moon.
And you still absolutely refuse to answer a simple yes/sometimes/no question regarding the above diagram.
--snip--
Seriously, what's your best guess about the volt meters in the above diagram? Do you think they would sum to zero? or not? or just sometimes?
Maybe it would help you to visualize real world values. How about 100mV per turn induced emf in the transformer core, and each resistor is 50 ohms.
Dude, lighten up and just answer the question so we can move on. Say "Yes, No, or Sometimes" and there's always the ever popular "I don't know" if that is your case, but if you don't know then you really don't know do you.
If this was chess, you're acting like you're in check. You're acting like you don't want to make a move because you know it'll put you in a bind you can't get out of.
I'm not asking you to try and follow some twisted mental gymnastics and draw a secret diagram I have in my mind.
I drew a simple real-world diagram which you can test yourself with a real transformer and real volt meter and resistors if you want, or if you already know the answer you can just give the answer.
If you can't do that, there's no way the other stuff you're asking is ever going to make sense.
Will the volt meters sum to zero in the above diagram in a real world test? Yes, Sometimes, No.
Thank you!
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
Emphasis mine. (Sredni, are you seeing this?!)
Oh my goodness. You think that because energy is conserved that fields must also be conserved? This is just - I don't even know what to say. :-\
Oh dear oh dear oh dear:
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/ (https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/)
It's amazing that you heard me say "the Lewin circuit demonstrates path dependence of non-conservative fields" and INSTANTLY thought this must be about conservation of energy. They're... not the same. You think conserved fields and conserved energy are descriptions of the same thing? :(
So yea, I guess you should review Newtonian mechanics before we deal with things like circulating magnetic fields:
https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf (https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf)
But I don't even know why I'm linking things for you - you're clearly not opening and reading them.
And I read your post with the circuit - Sredni asked you questions about it that you never answered.
Wow, you sound a lot like bsfeechannel. Your ignorance hurts! Three questions for you: 1) How many fields do we have in the loop circuit with two resistors? 2) What is the instantaneous power induced in the circuit by the external varying magnetic field? 3) What is the instantaneous power consumed by the circuit? The answers are three real numbers. Anything else you say is BS.
Don't ask Sredni for help, he is busy trying to calculate the voltage between nodes 'A' and 'D', VAD.
Ah you refuse to learn about energy conservation as opposed to field conservation. No wonder Faraday's Law seems like a big inscrutable mystery that only KVL can save you from.
Did you open any of those links? Have you opened anything I've linked? Have you read Kraus, chapter 4? Or chapter 10? It's easy to find online.
Let me guess, you're going to say...
"That's all BS!"
I understand your diversionary tactics and I will not fall for them. Let us concentrate in the solution of Lewin's original problem. Now, the three numerical answers are:
1) ____ fields.
2) ____ W.
3) ____ W.
Fill in the blanks.
And... you don't understand what 'conservative' means when taking about circuits. It is the energy that is conservative! In Lewin's circuit, what is the instantaneous power induced in the circuit by means of the external magnetic field? Now, what is the instantaneous power dissipated by the resistors? Come on, is not a hard calculation! If the two are equal, then the fields (plural) are conservative.
Emphasis mine. (Sredni, are you seeing this?!)
Oh my goodness. You think that because energy is conserved that fields must also be conserved? This is just - I don't even know what to say. :-\
Oh dear oh dear oh dear:
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/ (https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/)
It's amazing that you heard me say "the Lewin circuit demonstrates path dependence of non-conservative fields" and INSTANTLY thought this must be about conservation of energy. They're... not the same. You think conserved fields and conserved energy are descriptions of the same thing? :(
So yea, I guess you should review Newtonian mechanics before we deal with things like circulating magnetic fields:
https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf (https://www.pearson.com/content/dam/one-dot-com/one-dot-com/us/en/higher-ed/en/products-services/course-products/wolfson-3e-info/pdf/sample-chapter--ch07.pdf)
But I don't even know why I'm linking things for you - you're clearly not opening and reading them.
And I read your post with the circuit - Sredni asked you questions about it that you never answered.
Wow, you sound a lot like bsfeechannel. Your ignorance hurts! Three questions for you: 1) How many fields do we have in the loop circuit with two resistors? 2) What is the instantaneous power induced in the circuit by the external varying magnetic field? 3) What is the instantaneous power consumed by the circuit? The answers are three real numbers. Anything else you say is BS.
Don't ask Sredni for help, he is busy trying to calculate the voltage between nodes 'A' and 'D', VAD.
Ah you refuse to learn about energy conservation as opposed to field conservation. No wonder Faraday's Law seems like a big inscrutable mystery that only KVL can save you from.
Did you open any of those links? Have you opened anything I've linked? Have you read Kraus, chapter 4? Or chapter 10? It's easy to find online.
Let me guess, you're going to say...
"That's all BS!"
I understand your diversionary tactics and I will not fall for them. Let us concentrate in the solution of Lewin's original problem. Now, the three numerical answers are:
1) ____ fields.
2) ____ W.
3) ____ W.
Fill in the blanks.
So the answer is no, no, and no.
Ah you're right. Faraday's Law fields are always conservative. You win.
...
Nah, even a lie that big is too much for me to utter without laughing in your face. :-DD :-DD
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)If you place your voltmeters all in the same simply connected region that does not include the variable dB/dt region, then yes of course KVL will work. It's written in the top right corner of the picture I have posted more then a week ago. You still have to understand that?
https://i.postimg.cc/jdJntBXT/20211128-121506.jpg (https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
My question is a simple yes or no question. Either the volt meters will sum to zero or they won't. Or maybe you think they might some days depending on the phase of the moon.
And you still absolutely refuse to answer a simple yes/sometimes/no question regarding the above diagram.
--snip--
Seriously, what's your best guess about the volt meters in the above diagram? Do you think they would sum to zero? or not? or just sometimes?
Maybe it would help you to visualize real world values. How about 100mV per turn induced emf in the transformer core, and each resistor is 50 ohms.
Dude, lighten up and just answer the question so we can move on. Say "Yes, No, or Sometimes" and there's always the ever popular "I don't know" if that is your case, but if you don't know then you really don't know do you.
If this was chess, you're acting like you're in check. You're acting like you don't want to make a move because you know it'll put you in a bind you can't get out of.
I'm not asking you to try and follow some twisted mental gymnastics and draw a secret diagram I have in my mind.
I drew a simple real-world diagram which you can test yourself with a real transformer and real volt meter and resistors if you want, or if you already know the answer you can just give the answer.
If you can't do that, there's no way the other stuff you're asking is ever going to make sense.
Will the volt meters sum to zero in the above diagram in a real world test? Yes, Sometimes, No.
Thank you!
This reminds me of when I was a kid. My cousin has this motorcycle - more of a scooter - that had to be started by jumping on a sort of lever. It never started at the first jolt. It usually needed three or four jumps.
I wonder if it's the same with you.
Here. Reread my answer. I'll add a few cues.
Here's the picture I was talking about:
(https://i.postimg.cc/Yq1ZDcPY/KVL-works-if-I-leave-out-the-magnetic-region.jpg)
It's literally titled: "KVL-works-if-I-leave-out-the-magnetic-region.jpg"
Does the ".jpg" confuse you? Or is it the dashes?
If you look at the top right corner, it says: "KVL works here".
What part of "KVL works here" you do not understand? "KVL"? "works"? "here"?
I hope it is clear that if you choose to look at a lumpABLE circuit as a lumpED circuit, then KVL works.
Wrooom... wrooom.... ?
?
Maybe that tank of yours is empty?
You are back! Have you figured out how to CALCULATE the voltage between nodes 'A' and 'D' yet? Show us!
You are back! Have you figured out how to CALCULATE the voltage between nodes 'A' and 'D' yet? Show us!
Your tank is sure dry.
Because I have already told you at least four times that it depends on the path, and I have calculated it for two paths already.
WHERE are you seeing "transformer secondaries"? You're evading answering again.
I edited that post to show the extra secondary in my diagram, also updated the text as well.
You're basically saying I can move my volt meter probes to measure AF instead of AB and get a different reading, therefore AB is ambiguous.
(https://i.postimg.cc/bNr4Wmwk/20211130-124903.jpg)
That's a really really weak argument, because you could just as well say that any reading is ambiguous because by moving the probes to another part of the circuit we get a different reading.
But if it's the best you got, polish it to shine as bright as you can.
Nope. Where in MY diagram do you see "transformer secondaries". Point them out, please.
My diagram literally shows the same topology as yours including the additional secondary.
But if you want me to actually show it in your diagram, fine, I'll do it after you answer the following YES or NO question. I asked you before and you refuse to answer me.
Question: In the following diagram, in a real life physical lab test performed with real (time synchronized) volt meters with a real transformer and real resistors CONNECTED AS SHOWN, will the readings of all the volt meters sum to zero, within the accuracy and resolution limitations of the volt meters? YES or NO.
(Or if you believe SOMETIMES is the answer, then explain one scenario for a YES condition and one scenario for a NO condition WITH THE VOLT METERS CONNECTED AS SHOWN - Running additional conductors through the transformer core is not allowed - nor is removing existing conductors from through the transformer core!)
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
Seriously, other than intentional repositioning of probes or intentional changes of details inside my lumped elements, all the measurements above are unambiguous.
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)If you place your voltmeters all in the same simply connected region that does not include the variable dB/dt region, then yes of course KVL will work. It's written in the top right corner of the picture I have posted more then a week ago. You still have to understand that?
https://i.postimg.cc/jdJntBXT/20211128-121506.jpg (https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
My question is a simple yes or no question. Either the volt meters will sum to zero or they won't. Or maybe you think they might some days depending on the phase of the moon.
And you still absolutely refuse to answer a simple yes/sometimes/no question regarding the above diagram.
--snip--
Seriously, what's your best guess about the volt meters in the above diagram? Do you think they would sum to zero? or not? or just sometimes?
Maybe it would help you to visualize real world values. How about 100mV per turn induced emf in the transformer core, and each resistor is 50 ohms.
Dude, lighten up and just answer the question so we can move on. Say "Yes, No, or Sometimes" and there's always the ever popular "I don't know" if that is your case, but if you don't know then you really don't know do you.
If this was chess, you're acting like you're in check. You're acting like you don't want to make a move because you know it'll put you in a bind you can't get out of.
I'm not asking you to try and follow some twisted mental gymnastics and draw a secret diagram I have in my mind.
I drew a simple real-world diagram which you can test yourself with a real transformer and real volt meter and resistors if you want, or if you already know the answer you can just give the answer.
If you can't do that, there's no way the other stuff you're asking is ever going to make sense.
Will the volt meters sum to zero in the above diagram in a real world test? Yes, Sometimes, No.
Thank you!
This reminds me of when I was a kid. My cousin has this motorcycle - more of a scooter - that had to be started by jumping on a sort of lever. It never started at the first jolt. It usually needed three or four jumps.
I wonder if it's the same with you.
Here. Reread my answer. I'll add a few cues.
Here's the picture I was talking about:
(https://i.postimg.cc/Yq1ZDcPY/KVL-works-if-I-leave-out-the-magnetic-region.jpg)
It's literally titled: "KVL-works-if-I-leave-out-the-magnetic-region.jpg"
Does the ".jpg" confuse you? Or is it the dashes?
If you look at the top right corner, it says: "KVL works here".
What part of "KVL works here" you do not understand? "KVL"? "works"? "here"?
I hope it is clear that if you choose to look at a lumpABLE circuit as a lumpED circuit, then KVL works.
Wrooom... wrooom.... ?
?
Maybe that tank of yours is empty?
You are back! Have you figured out how to CALCULATE the voltage between nodes 'A' and 'D' yet? Show us!
Your tank is sure dry.
Because I have already told you at least four times that it depends on the path, and I have calculated it for two paths already.
Nope. The answers you provided are the voltages MEASURED by the 'voltmeters' on the left and right. CALCULATE the voltage VAD; you can use either the left branch or the right branch.
It's really funny how one of you insists on calculations and the other one on voltmeter readings being "truth". You really need to clean up your act before you go on stage.
You are back! Have you figured out how to CALCULATE the voltage between nodes 'A' and 'D' yet? Show us!
Your tank is sure dry.
Because I have already told you at least four times that it depends on the path, and I have calculated it for two paths already.
Nope. The answers you provided are the voltages MEASURED by the 'voltmeters' on the left and right. CALCULATE the voltage VAD; you can use either the left branch or the right branch.
I calculated the voltages measured by the voltmeters. These are also the voltages from probe tip to probe tip, because I do not have silly tiny batteries in my probe wires. And I can compute the voltages along the two branches of the circuit that join A and D: one branch through R1 and one branch through R2 (can't use KVL like for Lewin's ring, becase all measurement loops are cutting the flux, so I'll have to use Faraday for those as well). And I can also compute the voltage along a path that joins A and D and cuts the magnetic flux region in two equal parts. Or along a path that draws Snoopy's profile.
But what's the point? You wouldn't understand.
Blah blah blah. Are you going to answer or not?
It's really funny how one of you insists on calculations and the other one on voltmeter readings being "truth". You really need to clean up your act before you go on stage.
It's really funny how one of you insists on calculations and the other one on voltmeter readings being "truth". You really need to clean up your act before you go on stage.
We're grinding both angles because Team Lewin can neither calculate nor measure reality.
Correct calculations like Belcher and McDonald did agree with measurements. Team KVL is on the same page.
Team Lewin, on the other hand, is all over the board.
But the more they realize they are in check, the less willing they become to answer questions, as they find out their understanding of reality is so far off base they dare not show their hand.
It's really funny how one of you insists on calculations and the other one on voltmeter readings being "truth". You really need to clean up your act before you go on stage.
Hey! I have both calculations and measurements:
Calculated:
V1=-24mV
V2=216mV
Vx=-136mV
Vy=-56mV
VAD=-96mV
Measured:
V1=-24.4mV
V2=212mV
Vx=-134mV
Vy=-56mV
VAD=-96mV
I have yet to see any measurements from team Lewin. Also, the only one doing calculations in team Lewin is Sredni. Sadly he can not figure how to calculate VAD.
Well gents,
we've come full circle ha ha ha :-DD :-DD :-DD
Supposing you're right that I'm clueless, one thing I do know is that Team Lewin seems to think they in check.
Team Lewin is unwilling or unable to answer simple yes/no/sometimes to a pivotal question (reproduced below for reference) as if they believe they are in a bind.
You are back! Have you figured out how to CALCULATE the voltage between nodes 'A' and 'D' yet? Show us!
Your tank is sure dry.
Because I have already told you at least four times that it depends on the path, and I have calculated it for two paths already.
Nope. The answers you provided are the voltages MEASURED by the 'voltmeters' on the left and right. CALCULATE the voltage VAD; you can use either the left branch or the right branch.
I calculated the voltages measured by the voltmeters. These are also the voltages from probe tip to probe tip, because I do not have silly tiny batteries in my probe wires. And I can compute the voltages along the two branches of the circuit that join A and D: one branch through R1 and one branch through R2 (can't use KVL like for Lewin's ring, becase all measurement loops are cutting the flux, so I'll have to use Faraday for those as well). And I can also compute the voltage along a path that joins A and D and cuts the magnetic flux region in two equal parts. Or along a path that draws Snoopy's profile.
But what's the point? You wouldn't understand.
First, let me clarify some terminology: the proper name is not 'silly tiny batteries'; it is 'voltage sources'. Now remove the 'voltmeters', and you only have the loop and the two resistors R1 and R2 and the varying external magnetic field. What is the voltage between nodes 'A' and 'D'? I think you already figured it out (how else would have you found Vx and Vy?), but you don't want to contradict Lewin's incorrect answer in which you have invested so much effort...
You really, really, really don't get it eh?
Ok. Here is my computed value for Vad - I call it VBA, just because I can
VBA(along left voltmeter) = -136 mV
VBA(along right voltmeter) = -56 mV
VBA(along circuit branch with R1) = +24 mV
VBA(along circuit branch with R2) = -216 mV
VBA(along line that splits the core in two) = -96 mV
VBA(along line that splits the core in 3/8 - 5/8) = -86 mV
VBA(along line that splits the core in 5/8 - 3/8) = -116 mV
VBA(along Snoopy profile) = - 100 mV
Why so many values?
Because...
--- drum roll ---
THE ****ING VOLTAGE DEPENDS ON THE ****ING PATH!!!
Tip, if you account for the induced EMF in the wires of the path you choose,
Maxwellians. People like Sredni aren't suggesting that KVL must hold even when it doesn't. It's not one of Maxwell's Equations - it's not sacred. So why the desperation to save it? Why is it so very important that KVL applies to the Lewin/Romer Ring? Well I don't know why. This is why Sredni is fascinated by the cognitive bias - why does everyone want to save KVL so badly?
Well gents,
we've come full circle ha ha ha :-DD :-DD :-DD
Supposing you're right that I'm clueless, one thing I do know is that Team Lewin seems to think they in check.
Ever been playing chess with someone and they think they are in check and they are taking forever and don't want to move, because they think it may be checkmate after that?
Team Lewin is unwilling or unable to answer simple yes/no/sometimes to a pivotal question (reproduced below for reference) as if they believe they are in a bind.
In my opinion it has been clearly established with experimental results and mathematically that KVL holds in the below diagram as well as in Lewin's circuit, as Dr. McDonald says.
The absolute refusal on the part of Team Lewin to even admit to the appearance of KVL holding in the below diagram further confirms their belief that they are cornered on the topic and they do see it as a pivotal question.
You might say that my question below is not pivotal, but looking at the amount of effort Team Lewin has put in trying to avoid answering "Yes" or "No" tells me that it is in fact a pivotal question.
In light of the fact that Team Lewin refuses to embrace (or even admit to) observable reality, it is clear this discussion isn't going to do any good in any short amount of time, and as I need to work if I want to get paid and this isn't what I get paid to do, I'm going to have to reduce the amount of time I enjoy here, so let's see if I can reduce my interaction to a day or two a week.
I do not get notice of comments here, but if you PM me then I get an email notification, so if somebody actually answers my question for real, please PM me and let me know!
In other news, I've begun to suspect that ads are playing on my youtube videos which really irks me because I don't upload videos for money and I don't make anything from it and even if I did with 15 videos and 12 subscribers it wouldn't be any money at all - so youtube is running intrusive ads and not paying me and not giving me a choice. If they allowed me to monetize then maybe I could go in and turn ads off for each video, but I can't even try that since they won't allow me to monetize.
Long and the short of it is I'm trying out Vimeo free - I dunno if they are better but I uploaded a couple test videos.
Does this work better? No ads?
https://vimeo.com/651687593
And actually, we can all probably see each other in that video ha ha ha ha :-DD :-DD :-DD
We're all just aphids with this huge shadow :-DD :-DD :-DD
(Actually Snedri, when I saw that aphid crawling along with a huge shadow I thought of your antics here, that's why I filmed it. But I imagine you probably see KVLer's the same way.)
Question: In the following diagram, in a real life physical lab test performed with real (time synchronized) volt meters with a real transformer and real resistors CONNECTED AS SHOWN, will the readings of all the volt meters sum to zero, within the accuracy and resolution limitations of the volt meters? YES or NO.
(Or if you believe SOMETIMES is the answer, then explain one scenario for a YES condition and one scenario for a NO condition WITH THE VOLT METERS CONNECTED AS SHOWN - Running additional conductors through the transformer core is not allowed - nor is removing existing conductors from through the transformer core!)
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
Maxwellians. People like Sredni aren't suggesting that KVL must hold even when it doesn't. It's not one of Maxwell's Equations - it's not sacred. So why the desperation to save it? Why is it so very important that KVL applies to the Lewin/Romer Ring? Well I don't know why. This is why Sredni is fascinated by the cognitive bias - why does everyone want to save KVL so badly?
I had a physics teacher in high school who used to say “A law is a law and always holds”. He said that because at least my generation had grown up watching Wile E. Coyote fly off a cliff in a horizontal trajectory, stop and, only after he realized there was no ground under his feet, free fall vertically.
People were confused when exactly the laws of motion were valid. If an object is thrown horizontally, does gravity act on it all the time or only when it cannot sustain a flight? Of course gravity acts all the time. So, to avoid having to think too much, teachers convey this idea that the laws of physics always hold.
Since KVL and KCL are presented as laws (Kirchhoff himself called them theorems, not laws), that’s what they think.
When these people go to get their EE degree, the professors don’t give enough emphasis on the fact that KCL and KVL only hold under certain conditions and that Maxwell’s equations are the complete description of the electromagnetic phenomenon.
The result is people like Dave, Mehdi, Jesse, jesuscf and others who think KVL/KCL and Maxwell’s equations are two concurrent and equivalent theories. One is a clever simplification, they reckon, used by engineers and the other, more complicated, is there to maintain the intellect of physicists occupied. They don’t understand that the “more complicated” theory exists because the “clever simplification” is incomplete.
They get an aversion for calculus and Maxwell’s equations. treat RF superficially and consider any insight on the subject as black magic. In fact they use KVL and KCL to discourage people from going down the maxwellian rabbit hole. They can’t explain any electromagnetic phenomenon if they can’t model it using lumped components.
Dave can’t understand how energy in a DC circuit flows in the fields. Of course. The only components he knows that transfer energy in the fields are capacitors and transformers. Both interrupt any galvanic connection between both sides of the circuits they connect and they block DC.
Look at his cringe-worthy post on Twitter about this.
https://twitter.com/eevblog/status/1465447319663374338?s=20 (https://twitter.com/eevblog/status/1465447319663374338?s=20)
They struggle to interpret their measurements and some of them think that what makes you an engineer is your oscilloscope (goto 39).
It’s worse when these guys, in good faith, have taught KVL and KCL as always holding for years to hundreds of thousands of viewers. As Mehdi himself said in this very interview, it must be difficult to be wrong in front of a million people.
So that’s why KVLers cling to the KVL myth.
I think that the teaching of electromagnetism in schools and colleges must be radically changed. They need to go beyond Lewin and tell students that their whole lives are a lie.
Tip, if you account for the induced EMF in the wires of the path you choose,
Well, the really funny thing is... I do account for the induced electric field, while you don't.
You don't know that yet, but the reason you can have a conservative field that admits a scalar potential is that... you have stripped away the contribute of the induced field. It will be revealed in the upcoming post:
"The tiny batteries model, or: 'I don't think that field is what you think it is.' "
that you will misunderstand, of course.
Hey bsfeechannel, do you have an electrical engineering degree (or similar) from an accredited institution? I am asking because the Dunning-Kruger is very strong in you.
Hey bsfeechannel, do you have an electrical engineering degree (or similar) from an accredited institution? I am asking because the Dunning-Kruger is very strong in you.
Hey jesuscf, you showed a few posts ago your absolute stupidity about conservative and non-conservative fields. Who are you kidding?
Without that fundamental concept, you will not understand what Lewin, Belcher, McDonald, Maxwell, Faraday, or any of us are talking about.
Really? So, you should not have any problem answering these questions then:
1) How many fields do we have in the loop circuit with two resistors? 2) What is the instantaneous power induced in the circuit by the external varying magnetic field? 3) What is the instantaneous power consumed by the circuit? The answers are three real numbers.
1) ____ fields.
2) ____ W.
3) ____ W.
I'll be waiting!
EDIT: Sorry, I got distracted. So, do you have a degree or not?
Well gents,
we've come full circle ha ha ha :-DD :-DD :-DD
Supposing you're right that I'm clueless, one thing I do know is that Team Lewin seems to think they in check.
Another victory lap.
You are restless.QuoteTeam Lewin is unwilling or unable to answer simple yes/no/sometimes to a pivotal question (reproduced below for reference) as if they believe they are in a bind.
The projection is strong in you.
Here is your answer. I wrote YES very big, so you can't miss it.
Read it all. Enjoy.
(https://i.postimg.cc/43tS42YM/KVL-works-YEEESSSSS-Sorta.jpg)
https://i.postimg.cc/43tS42YM/KVL-works-YEEESSSSS-Sorta.jpg
TL;DR I lost, but I won't admit it. I'll even claim victory, like any good KVLer.
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire? Using the same model it is fairly easy to explain the voltage measured across each resistor:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
(https://i.postimg.cc/1tNL2Mmn/20211122-214739.jpg)
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
<removed the image>
Really? I wouldn't be surprised at all.
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
<removed the image>
Really? I wouldn't be surprised at all.
I would, because that is violating the Ohm's law (U = I*R, and when R is 0 ohms, the voltage should be 0 too), which means that my probing is picking up some interference from some magnetic field affecting my measurements.
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
<removed the image>
Really? I wouldn't be surprised at all.
I would, because that is violating the Ohm's law (U = I*R, and when R is 0 ohms, the voltage should be 0 too), which means that my probing is picking up some interference from some magnetic field affecting my measurements.
The reason you are surprised is because you gazed into the aby-- into the forbidden zone where the magnetic flux changes.
There, KVL dies.
(To clarify: voltage becomes path dependent and so you can have zero voltage ALONG the conductor in compliance with Ohm's law, and nonzero voltage ACROSS the terminals as you can measure with your voltmeter or oscilloscope)
But if you hide that part of space inside a black box, you will see a nonzero voltage 'across' a generator's terminals. Not surprising at all.
This is the point KVLers seem unable to understand. KVL dies right inside every transformer's secondary. We choose not to see that by not looking inside. But it's all just make-believe.
I just wanted to point this out because in this particular case I know that I am measuring voltage V1 across a 0 ohm wire, but my instrument is showing some other voltage than zero violating the Ohm's law, which is a clear indication that there is something wrong in my probing, and the measurement setup is picking up interference from some magnetic field affecting my measurement.
I just wanted to point this out because in this particular case I know that I am measuring voltage V1 across a 0 ohm wire, but my instrument is showing some other voltage than zero violating the Ohm's law, which is a clear indication that there is something wrong in my probing, and the measurement setup is picking up interference from some magnetic field affecting my measurement.
What I am saying is that
1. That voltage is NOT interference: it's exactly what that piece of system is supposed to do (hence your probing is correct: you put a voltmeter across the secondary of a transformer and the 12V you measure are not 'interference', despite the fact that if you follow the magnet wires inside the device all you see is... wire)
2. Ohm's law is obeyed (if you use the correct physics, of course)
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire? Using the same model it is fairly easy to explain the voltage measured across each resistor:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
I'd say, your calculation of V1 and V2 is 5.555mV off. Also there's no reason why the voltage across any of the resistors should be different from what Ohm's Law says.
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire? Using the same model it is fairly easy to explain the voltage measured across each resistor:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
I'd say, your calculation of V1 and V2 is 5.555mV off. Also there's no reason why the voltage across any of the resistors should be different from what Ohm's Law says.
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire? Using the same model it is fairly easy to explain the voltage measured across each resistor:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
I'd say, your calculation of V1 and V2 is 5.555mV off. Also there's no reason why the voltage across any of the resistors should be different from what Ohm's Law says.
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
I'm not quite sure why the resistance along the path would make a difference. A series of resistors is not fundamentally different from a wire with the same resistance.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire?
...
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire?
...
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
What's the matter, pretty boy? You can't find your EMF?
(Sorry, I could not resist)
I am glad I have this message to reply to! Why? Because I just found the solution to Lewin's problem in an Electromagnetics book! And it doesn't look good at all for team Lewin. The book is "Electromagnetics" by Branislav M. Notaros, pages 279 and 280 (the edition I have is from 2011). The example is 6.6. I have attached the pages to this message. Sredni, now you have a bibliographical reference that can teach you how to calculate the voltage VAD. Don't forget to pay attention to Figure 6.10(b)!
EDIT: fixed page numbers
How do you explain the situation where the whole ring is made of resistors, with virtually no wire?
...
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
What's the matter, pretty boy? You can't find your EMF?
(Sorry, I could not resist)
I am glad I have this message to reply to! Why? Because I just found the solution to Lewin's problem in an Electromagnetics book! And it doesn't look good at all for team Lewin. The book is "Electromagnetics" by Branislav M. Notaros, pages 279 and 280 (the edition I have is from 2011). The example is 6.6. I have attached the pages to this message. Sredni, now you have a bibliographical reference that can teach you how to calculate the voltage VAD. Don't forget to pay attention to Figure 6.10(b)!
I am glad I have this message to reply to! Why? Because I just found the solution to Lewin's problem in an Electromagnetics book! And it doesn't look good at all for team Lewin. The book is "Electromagnetics" by Branislav M. Notaros, pages 279 and 280 (the edition I have is from 2011). The example is 6.6. I have attached the pages to this message. Sredni, now you have a bibliographical reference that can teach you how to calculate the voltage VAD. Don't forget to pay attention to Figure 6.10(b)!
EDIT: fixed page numbers
Notaros says that if σ1 = σ2, then vMN = 0. Incredible! You have two wire resistors with zero volts across their terminals and a current that is iind = eind / (R1 + R2).
Oh yeah, of course. What Notaros didn't tell you, because he obviously presumes you already understand the effect of non-conservative electric fields, is that this voltage is calculated along a straight line between points M and N.
Once defined this path you can model it using mundane circuit theory. No problem. No one is against that.
Build the circuit, immerse it in the varying magnetic field, place your meter right in the middle with the probes stretched along a straight line between M and N and you'll find vMN he calculated.
How do you explain the situation where the whole ring is made of resistors, with virtually no wire?
...
If that is the case, where is the induced EMF coming from? Remember, there is no wire in the loop, only resistors, and the only access points to the circuit are the terminals of the resistors.
What's the matter, pretty boy? You can't find your EMF?
(Sorry, I could not resist)
I am glad I have this message to reply to! Why? Because I just found the solution to Lewin's problem in an Electromagnetics book! And it doesn't look good at all for team Lewin. The book is "Electromagnetics" by Branislav M. Notaros, pages 279 and 280 (the edition I have is from 2011). The example is 6.6. I have attached the pages to this message. Sredni, now you have a bibliographical reference that can teach you how to calculate the voltage VAD. Don't forget to pay attention to Figure 6.10(b)!
Soooo... the EMF is located on top of the resistors, it seems. Half just above R1, and half just above R2. How many centimeters, exactly? The text does not say. Can you locate with a bit more accuracy? No?
Or maybe...
Maybe that's the "equivalent circuit" that allows you to "solve the problem from the circuit theory point of view" and that is one of the introductory textbooks that do not explain clearly to their easily distracted audience what they intend for V. Oh, wait, but it does explain what V is! Page 269, eq. 6.18
Eq = - grad V
(Eq is what I call Ecoul) and V is... the electric scalar potential. Only half of the potentials required to describe the total electric field. And the text also says so explicitly on page 277, formula 6.43
E(t) = - dA/dt - grad V
"We see that both potentials are needed for E..."
(the same expression I used to express Etot = Eind + Ecoul, even if recently I decided to call the scalar electric potential phi, instead of V - exactly to avoid this kind of confusion you are having)
So...
where is exactly the EMF, again?
(Lewin problem is solved as an exercise on Purcell, Morin: Berkeley Physics vol 2, Electricity and Magnetism 3rd edition)
Oh boy bsfeechannel, you are very special, but not in a good way! In figure 6.10(b) what is the voltage between nodes vMN if R1 is equal to R2?
Oh boy bsfeechannel, you are very special, but not in a good way! In figure 6.10(b) what is the voltage between nodes vMN if R1 is equal to R2?
Who cares about figure 6.10(b)? It's an equivalent circuit. It's an imaginary construct, a math trick. It doesn't exist.
The real circuit is described by figure 6.10(a). There is where you'll come a gutser.
https://www.youtube.com/watch?v=xMePTKuAixE (https://www.youtube.com/watch?v=xMePTKuAixE)
PS: "Team KVL", don't get your hopes up too early ;)
I just wanted to point this out because in this particular case I know that I am measuring voltage V1 across a 0 ohm wire, but my instrument is showing some other voltage than zero violating the Ohm's law, which is a clear indication that there is something wrong in my probing, and the measurement setup is picking up interference from some magnetic field affecting my measurement.
What I am saying is that
1. That voltage is NOT interference: it's exactly what that piece of system is supposed to do (hence your probing is correct: you put a voltmeter across the secondary of a transformer and the 12V you measure are not 'interference', despite the fact that if you follow the magnet wires inside the device all you see is... wire)
2. Ohm's law is obeyed (if you use the correct physics, of course)
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
Well, it's a Nothing Burger, how our host would be calling it. While you can calculate a voltage for Vad, it is more mathturbation than anything else.
It is not trivial to compute for other than artificial setups with simple paths, perfect symmetry or at least uniformity of the electric field, and actually observing it is also quite complicated, because all measurements would again be taken along paths through a non-conservative electric field, which adds another dimension of error.
So, you'd compute a value for Vad, making various assumptions about the fields involved, then calculate a path based on the same assumptions, then try to make your measurements and calculations match in reality. But at no point you would be sure if any of it is correct. Plus there are geometries where it is not possible to measure it.
The same guy has a good video on the merits of PD to "salvage KVL" on his channel. It is quite thorough IMHO, though a bit long winded, but still worth watching in detail.
https://youtu.be/I1kYKF2x9Ns (https://youtu.be/I1kYKF2x9Ns)
https://www.youtube.com/watch?v=xMePTKuAixE (https://www.youtube.com/watch?v=xMePTKuAixE)
PS: "Team KVL", don't get your hopes up too early ;)
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
Although the video you linked is correct, I think it goes in to too much detail and sometimes it is hard to decipher what he tries to explain. In my opinion this video from Bob Duhamel from RSD Academy explains it better:
https://www.youtube.com/watch?v=aQB871ku6a8 (https://www.youtube.com/watch?v=aQB871ku6a8)
https://www.youtube.com/watch?v=xMePTKuAixE (https://www.youtube.com/watch?v=xMePTKuAixE)
PS: "Team KVL", don't get your hopes up too early ;)
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
The point is this:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338011;image)
What he calculated was the scalar potential difference between those two points and he points out [pun unintended] how difficult or even impossible would be to measure it. The voltages measured by the voltmeters in his calculations match exactly what Lewin predicted and then he, Mehdi, and many others measured: two different voltages.
So, if you're saying the video is correct, this means that you are recognizing that Lewin is absolutely right and Mehdi is dead wrong. Congratulations.
https://www.youtube.com/watch?v=xMePTKuAixE (https://www.youtube.com/watch?v=xMePTKuAixE)
PS: "Team KVL", don't get your hopes up too early ;)
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
The point is this:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338011;image)
What he calculated was the scalar potential difference between those two points and he points out [pun unintended] how difficult or even impossible would be to measure it. The voltages measured by the voltmeters in his calculations match exactly what Lewin predicted and then he, Mehdi, and many others measured: two different voltages.
So, if you're saying the video is correct, this means that you are recognizing that Lewin is absolutely right and Mehdi is dead wrong. Congratulations.
Just carry on watching a bit longer, and try to understand what he is saying!
I just wanted to point this out because in this particular case I know that I am measuring voltage V1 across a 0 ohm wire, but my instrument is showing some other voltage than zero violating the Ohm's law, which is a clear indication that there is something wrong in my probing, and the measurement setup is picking up interference from some magnetic field affecting my measurement.
What I am saying is that
1. That voltage is NOT interference: it's exactly what that piece of system is supposed to do (hence your probing is correct: you put a voltmeter across the secondary of a transformer and the 12V you measure are not 'interference', despite the fact that if you follow the magnet wires inside the device all you see is... wire)
2. Ohm's law is obeyed (if you use the correct physics, of course)
This is what I came up with when thinking about this circuit and when KVL holds and doesn't hold.
In figure a) the circuit is inside a magnetic field, the voltage between points A and D depends on path, it is not possible to create a lumped model for the source creating the 1mA current, and KVL doesn't hold.
In figure b) the circuit is only partially inside a magnetic field creating a transformer with a single-turn secondary, thus it is possible to create a lumped model for the source creating the 1mA current like in figure c, and KVL holds.
Figure c is a lumped model for figure b with a (voltage) source creating the 1mA current when the magnetic field is increasing, and KVL holds.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1337789;image)
Is my reasoning correct?
Edit: Added some clarifications.
https://www.youtube.com/watch?v=xMePTKuAixE (https://www.youtube.com/watch?v=xMePTKuAixE)
PS: "Team KVL", don't get your hopes up too early ;)
The video is correct. He even calculates the correct and unique voltage between VAD (VJX at 33:38, something Lewin was unable to do), followed with an explanation of what happens if use KVL without including the induced EMF (what Lewin did). So, what is your point exactly?
The point is this:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338011;image)
What he calculated was the scalar potential difference between those two points and he points out [pun unintended] how difficult or even impossible would be to measure it. The voltages measured by the voltmeters in his calculations match exactly what Lewin predicted and then he, Mehdi, and many others measured: two different voltages.
So, if you're saying the video is correct, this means that you are recognizing that Lewin is absolutely right and Mehdi is dead wrong. Congratulations.
Just carry on watching a bit longer, and try to understand what he is saying!
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
Isn't it hilarious that KVLers be so obtuse that they can't even recognize when a video was made to debunk their claims, due to their absolute lack of understanding of what is being discussed?
Congratulations, Mehdi Sadaghdar! Look what you've done! You've spawned a whole bunch of brain-damaged mock engineers like yourself.
In figure a) the circuit is inside a magnetic field, the voltage between points A and D depends on path, it is not possible to create a lumped model for the source creating the 1mA current, and KVL doesn't hold.
In figure b) the circuit is only partially inside a magnetic field creating a transformer with a single-turn secondary, thus it is possible to create a lumped model for the source creating the 1mA current like in figure c, and KVL holds.
Figure c is a lumped model for figure b with a (voltage) source creating the 1mA current when the magnetic field is increasing, and KVL holds.
Is my reasoning correct?
Here is the circuit from Lewin's video with 1V voltage source.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting two antiparallel 1mA current sources between nodes D and A. After split, the currents and the voltages of the original circuit remain unchanged.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting a voltage source between nodes D and A with value V(D,A) because there is no current flowing through the new voltage source. After split, the currents and the voltages of the original circuit remain unchanged.
It can be seen that KVL holds and it is possible to spilt the circuit in half at D and A.
The 1V voltage source can be located some other point in the original circuit, which will affect the equivalent circuit values, but KVL will still hold.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338839;image)
Here is the circuit from Lewin's video when the solenoid is generating 1mA current flowing in the circuit. It can be seen that KVL fails when the circuit contains of non-conservative fields, and thus it is not possible to split the circuit at D and A.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338845;image)
I see, you too, are confused with the 'non-conservative fields' statement. Although it may appear that in the circuit the electric field is non-conservative because it is changing over time, so it is the magnetic field. What happens is that the the total energy in the circuit is conservative: all energy added to the circuit is consumed by the circuit. From the circuital point of view is easier to work with instantaneous power than energy. For example at time t when the EMF is 1V the calculated current is 1mA, then: EMF*I=I2(R1+R2). The external varying magnetic field is adding 1mW to the circuit and the circuit is consuming 1mW. The fields in the circuit are conservative.Emphasis mine.
I see, you too, are confused with the 'non-conservative fields' statement. Although it may appear that in the circuit the electric field is non-conservative because it is changing over time, so it is the magnetic field. What happens is that the the total energy in the circuit is conservative: all energy added to the circuit is consumed by the circuit. From the circuital point of view is easier to work with instantaneous power than energy. For example at time t when the EMF is 1V the calculated current is 1mA, then: EMF*I=I2(R1+R2). The external varying magnetic field is adding 1mW to the circuit and the circuit is consuming 1mW. The fields in the circuit are conservative.
I see, you too, are confused with the 'non-conservative fields' statement. Although it may appear that in the circuit the electric field is non-conservative because it is changing over time, so it is the magnetic field. What happens is that the the total energy in the circuit is conservative: all energy added to the circuit is consumed by the circuit. From the circuital point of view is easier to work with instantaneous power than energy. For example at time t when the EMF is 1V the calculated current is 1mA, then: EMF*I=I2(R1+R2). The external varying magnetic field is adding 1mW to the circuit and the circuit is consuming 1mW. The fields in the circuit are conservative.
He understands what a non conservative field is. You don't. That's why you think he's confused.
Here is the circuit from Lewin's video with 1V voltage source.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting two antiparallel 1mA current sources between nodes D and A. After split, the currents and the voltages of the original circuit remain unchanged.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting a voltage source between nodes D and A with value V(D,A) because there is no current flowing through the new voltage source. After split, the currents and the voltages of the original circuit remain unchanged.
It can be seen that KVL holds and it is possible to spilt the circuit in half at D and A.
The 1V voltage source can be located some other point in the original circuit, which will affect the equivalent circuit values, but KVL will still hold.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338839;image)
Here is the circuit from Lewin's video when the solenoid is generating 1mA current flowing in the circuit. It can be seen that KVL fails when the circuit contains of non-conservative fields, and thus it is not possible to split the circuit at D and A.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338845;image)
Here is the circuit from Lewin's video with 1V voltage source.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting two antiparallel 1mA current sources between nodes D and A. After split, the currents and the voltages of the original circuit remain unchanged.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting a voltage source between nodes D and A with value V(D,A) because there is no current flowing through the new voltage source. After split, the currents and the voltages of the original circuit remain unchanged.
It can be seen that KVL holds and it is possible to spilt the circuit in half at D and A.
The 1V voltage source can be located some other point in the original circuit, which will affect the equivalent circuit values, but KVL will still hold.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338839;image)
Here is the circuit from Lewin's video when the solenoid is generating 1mA current flowing in the circuit. It can be seen that KVL fails when the circuit contains of non-conservative fields, and thus it is not possible to split the circuit at D and A.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338845;image)
By the way, your equivalent circuit for the loop with the two resistors is incorrect. If you use the correct equivalent circuit:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1339286;image)
You will see that KVL holds even if you split the circuit as in the second set of your images.
Here is the circuit from Lewin's video with 1V voltage source.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting two antiparallel 1mA current sources between nodes D and A. After split, the currents and the voltages of the original circuit remain unchanged.
If the KVL holds, it possible to split the original circuit in half at D and A by inserting a voltage source between nodes D and A with value V(D,A) because there is no current flowing through the new voltage source. After split, the currents and the voltages of the original circuit remain unchanged.
It can be seen that KVL holds and it is possible to spilt the circuit in half at D and A.
The 1V voltage source can be located some other point in the original circuit, which will affect the equivalent circuit values, but KVL will still hold.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338839;image)
Here is the circuit from Lewin's video when the solenoid is generating 1mA current flowing in the circuit. It can be seen that KVL fails when the circuit contains of non-conservative fields, and thus it is not possible to split the circuit at D and A.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1338845;image)
By the way, your equivalent circuit for the loop with the two resistors is incorrect. If you use the correct equivalent circuit:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1339286;image)
You will see that KVL holds even if you split the circuit as in the second set of your images.
Please note that the original distributed circuit model in figure a below is not equivalent with the lumped circuit models in figures b and c. Your suggestion is identical with the lumped model in figure c with the voltage source split in half. However, your circuit is not identical with the original circuit any more, because you are transforming a non-conservative circuit into a conservative circuit by introducing those voltage sources. Thus I would say that your suggestion is not a valid transformation.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1337789;image)
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
(https://i.postimg.cc/1tNL2Mmn/20211122-214739.jpg)
Question: In the following diagram, in a real life physical lab test performed with real (time synchronized) volt meters with a real transformer and real resistors CONNECTED AS SHOWN, will the readings of all the volt meters sum to zero, within the accuracy and resolution limitations of the volt meters? YES or NO.
(Or if you believe SOMETIMES is the answer, then explain one scenario for a YES condition and one scenario for a NO condition WITH THE VOLT METERS CONNECTED AS SHOWN - Running additional conductors through the transformer core is not allowed - nor is removing existing conductors from through the transformer core!)
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
You do realize that this is not a circuit that is equivalent to the "Lewin Ring", or equivalent to the circuit I gave you to solve, right?
That was my challenge to you, the task was to find the voltages across the resistors and the wires:
(https://i.postimg.cc/dtbDygLj/IMG-20211119-112430.jpg)
And that's what you came up with:
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
Which of course brings up the question why you found it necessary to add a "transformer secondary" to find the voltage across "2R".
I didn't fly away,Oh, good. So you can answer my question, since I have answered yours.
I told you I unequivocally proved that Team Lewin absoutely refused to answer basic questions - EVERY SINGLE (then active) MEMBER of Team Lewin absolutely refused to answer my question. What's else to discuss when Team Lewin denies observable reality?
He too refused to answer numerous questions which I asked him, and also made false predictions about reality - in fact, when I told him that KVL would hold with a loop made from two transformer secondary windings and two resistors, he didn't believe me, so that's why I made the "KVL Holds with an iron core" video.
He too refused to answer my simple question that you all refused to answer - If it measures like it's working, why is it not working? is it a technicality?
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
I didn't fly away, I told you I unequivocally proved that Team Lewin absoutely refused to answer basic questions - EVERY SINGLE (then active) MEMBER of Team Lewin absolutely refused to answer my question. What's else to discuss when Team Lewin denies observable reality?
As I said, I need to limit my time here to a couple times a week because I get paid by the hour to do other work (Self employed) and things reached a stage where it was clear that Team Lewin is holding to their beliefs even if it means denying observable reality.
As you've seen from my youtube channel comments, Trevor Kearney is a very nice gent - but you will also see that he does not have as good a grasp of the topic as he thinks.
He too refused to answer numerous questions which I asked him, and also made false predictions about reality - in fact, when I told him that KVL would hold with a loop made from two transformer secondary windings and two resistors, he didn't believe me, so that's why I made the "KVL Holds with an iron core" video.
He too refused to answer my simple question that you all refused to answer - If it measures like it's working, why is it not working? is it a technicality?
There seem to be two kinds of people - those who live and breath reality and deal with math as needed, and those who live in the virtual world of math and deal with reality when needed.
Or in your case, deny observable reality.
I didn't fly away,Oh, good. So you can answer my question, since I have answered yours.QuoteI told you I unequivocally proved that Team Lewin absoutely refused to answer basic questions - EVERY SINGLE (then active) MEMBER of Team Lewin absolutely refused to answer my question. What's else to discuss when Team Lewin denies observable reality?
Maybe we did answer the question, and you are not able to accept the answer so you keep asking it over and over hoping to receive the answer you want?QuoteHe too refused to answer numerous questions which I asked him, and also made false predictions about reality - in fact, when I told him that KVL would hold with a loop made from two transformer secondary windings and two resistors, he didn't believe me, so that's why I made the "KVL Holds with an iron core" video.
He too refused to answer my simple question that you all refused to answer - If it measures like it's working, why is it not working? is it a technicality?
As I repeated about a dozen times, if a circuit is lumpABLE and you choose the circuit path in such a way that it does not include a variable magnetic field, then you can consider all voltages between any two points on that circuit path as if they were path independent. The circuit can be considered lumpED and KVL works.
IF the circuit is lumpABLE.
There are in our universe, circuits that are not lumpable: I call them UNlumpable circuits.
They are circuits where you cannot find a circuit path that does not encloses the variable flux region.
Lewin's ring IS such a circuit because it REQUIRES the two resistors to be on the opposite sides of a variable magnetic flux region.
You think Lewin's ring is lumpABLE?
Well, PROVE IT.
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
link https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminal to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
I would be a little concerned with my probing if I measured V1 something else than 0V across a 0 ohm wire [when |V2 + V3| > 0].
(https://i.postimg.cc/1tNL2Mmn/20211122-214739.jpg)
Don't forget that not all voltage differences are ohmic.
There's batteries, capacitors, solar cells, peltier junctions, and yes, the ever popular inductive transformer.
All of those things can have voltages across them which would appear to violate ohms law if we assume that all voltage differences are strictly ohmic.
not all voltage differences are purely ohmic.
And one of those that is not strictly ohmic is the winding of a transformer.
Did you get the voltage VAD yet? Do you need more help?
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
link https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg (https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Here is the problem with Notaros and a counter-example: Where would you put those voltage sources modeling the EMF so that you can measure the correct voltages across two neighboring resistors ie. V(Ra,Rb), V(Rb,Rc), V(Rc, Rf), V(Rf, Re), V(Re, Rd), V(Rd, Ra).
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1339760;image)
That was my challenge to you, the task was to find the voltages across the resistors and the wires:
(https://i.postimg.cc/dtbDygLj/IMG-20211119-112430.jpg)
And that's what you came up with:
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
Which of course brings up the question why you found it necessary to add a "transformer secondary" to find the voltage across "2R".
You call it an "added secondary" but it MEASURES AND MODELS the exact same as if the right hand volt meter was instead on the left. Doesn't matter where it is. It doesn't loop through the core, which means it's not another winding.
Remember, KVL requires two-terminal elements. If we're not using a two-terminal element, OF COURSE kvl isn't even applicable.
You want me to run a volt meter lead through the core which effectively adds another secondary winding, making it into a 3 terminal element, and as such, it's no longer applicable for KVL.
Dude, that's Trevor Kearney. If Jesse hadn't flown away to another galaxy to avoid answering my question on the circuit path for Lewin's ring, he would tell you Trevor is "Armchair Physics Nobel Prize" number one. He's probably one of the most active people on YouTube trying to debunk Mehdi and the other KVLers. :palm:
Isn't it hilarious that KVLers be so obtuse that they can't even recognize when a video was made to debunk their claims, due to their absolute lack of understanding of what is being discussed?
Congratulations, Mehdi Sadaghdar! Look what you've done! You've spawned a whole bunch of brain-damaged mock engineers like yourself.
I didn't fly away,Oh, good. So you can answer my question, since I have answered yours.
QuoteI told you I unequivocally proved that Team Lewin absoutely refused to answer basic questions - EVERY SINGLE (then active) MEMBER of Team Lewin absolutely refused to answer my question. What's else to discuss when Team Lewin denies observable reality?
Maybe we did answer the question, and you are not able to accept the answer so you keep asking it over and over hoping to receive the answer you want?
QuoteHe too refused to answer numerous questions which I asked him, and also made false predictions about reality - in fact, when I told him that KVL would hold with a loop made from two transformer secondary windings and two resistors, he didn't believe me, so that's why I made the "KVL Holds with an iron core" video.
He too refused to answer my simple question that you all refused to answer - If it measures like it's working, why is it not working? is it a technicality?
As I repeated about a dozen times, if a circuit is lumpABLE and you choose the circuit path in such a way that it does not include a variable magnetic field, then you can consider all voltages between any two points on that circuit path as if they were path independent. The circuit can be considered lumpED and KVL works.
IF the circuit is lumpABLE.
There are in our universe, circuits that are not lumpable: I call them UNlumpable circuits.
They are circuits where you cannot find a circuit path that does not encloses the variable flux region.
Lewin's ring IS such a circuit because it REQUIRES the two resistors to be on the opposite sides of a variable magnetic flux region.
You think Lewin's ring is lumpABLE?
Well, PROVE IT.
This is Lewin's ring: two resistors in a single loop that goes around a circular region (let's consider it of the same size as the loop, so you can see there is no 'room to twist' the wires) of variable magnetic field. The resistors are required to be on the opposite sides of the variable magnetic field region.
(https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg)
link https://i.postimg.cc/pLmfyHxZ/Lewin-ring-is-unlumpable.jpg
Please, show everybody you can draw a circuit path (make it green, meaning it's 'flux-free') that joins the resistors' terminal to the "lumped transformer secondary" terminals and DOES NOT INCLUDE the variable magnetic field region in its interior. Like I did for the lumpABLE circuit I decided to see as lumpED (in my post "Lumpable (lumped and not lumped) and not lumpable circuits for dummies").
In addition, you can also show everybody you can draw the path inside your "lumped transformer secondary" that DOES INCLUDE the variable magnetic field region (make it orange) but IS NOT part of the green circuit path.
I will show you that if you can do that you will run into contradiction.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Here is the problem with Notaros and a counter-example: Where would you put those voltage sources modeling the EMF so that you can measure the correct voltages across two neighboring resistors ie. V(Ra,Rb), V(Rb,Rc), V(Rc, Rf), V(Rf, Re), V(Re, Rd), V(Rd, Ra).
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1339760;image)
That is a very good question that has been answered in this forum many, many times: each resistor in the loop behaves both as voltage source a resistor in series. Check this post:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
That was my challenge to you, the task was to find the voltages across the resistors and the wires:
(https://i.postimg.cc/dtbDygLj/IMG-20211119-112430.jpg)
And that's what you came up with:
(https://i.postimg.cc/rs3cCg2F/20211119-122528.jpg)
Which of course brings up the question why you found it necessary to add a "transformer secondary" to find the voltage across "2R".
You call it an "added secondary" but it MEASURES AND MODELS the exact same as if the right hand volt meter was instead on the left. Doesn't matter where it is. It doesn't loop through the core, which means it's not another winding.
Remember, KVL requires two-terminal elements. If we're not using a two-terminal element, OF COURSE kvl isn't even applicable.
You want me to run a volt meter lead through the core which effectively adds another secondary winding, making it into a 3 terminal element, and as such, it's no longer applicable for KVL.
Before I go further into the details of why I think your explanation is rubbish, let me expand on "observable reality":
What is observed is not reality
until you've asked "Why is it so?" often enough to rule out all possible reasons but one. The idea of it being enough to just observe and not ask the "Why is it so?" question has directly lead to the creation of divine beings, or gods, to explain phenomena of nature in ancient cultures. People observed weather and the changing of seasons and as they were not able to explain and thus gods were created.
You, instead of asking the right questions, just try to confirm your beliefs. Instead of asking why the volt meters in Lewins experiment show different voltages you say "He's just a fool, he made a mistake, it's bad probing". When asked about the mechanism that induces voltage in a transformer winding you say "It's Nature".
I feel now that I did injustice to the flatearthers by likening you to them.
Because, as the Physicist Sabine Hossenfelder said about them, their science is wrong, but not stupid.
Anyway, thank you for answering my question about which of the loops in my diagram you consider a "transformer secondary" and which are not. I knew the answer beforehand of course, but I needed you to confirm it with your own words so that there will be no wiggling out of it later.
Lumped circuits are obtained by connecting lumped elements. Typical
lumped elements are resistors, capacitors, inductors, and transformers.
Quote from: KalvinHere is the problem with Notaros and a counter-example: Where would you put those voltage sources modeling the EMF so that you can measure the correct voltages across two neighboring resistors ie. V(Ra,Rb), V(Rb,Rc), V(Rc, Rf), V(Rf, Re), V(Re, Rd), V(Rd, Ra).
<removed the image>
That is a very good question that has been answered in this forum many, many times: each resistor in the loop behaves both as voltage source a resistor in series. Check this post:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Ok, tell me why you think the circuit is non-conservative.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
According to team Lewin the induced EMF due to Faraday's law is 'special'
(like themselves)
because something-something and can not be treated just like any other EMF despite that all of them are measured in volts...
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
What Notaros did was a math trick, very common in textbooks, but that unfortunately confuses KVLers. They think that if you model some circuit with an equivalent circuit, the components of that equivalent circuit will be found in the modeled circuit.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
Here is the problem with Notaros and a counter-example: Where would you put those voltage sources modeling the EMF so that you can measure the correct voltages across two neighboring resistors ie. V(Ra,Rb), V(Rb,Rc), V(Rc, Rf), V(Rf, Re), V(Re, Rd), V(Rd, Ra).
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1339760;image)
That is a very good question that has been answered in this forum many, many times: each resistor in the loop behaves both as voltage source a resistor in series. Check this post:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3830852/#msg3830852)
Fair enough, but my circuit has only six resistors. Where would you put those voltage sources modeling the EMF in the circuit so that it will be possible to measure correct voltages a) across each individual resistor, and b) across two consecutive resistors?
That is exactly the problem: the resistors are both behaving as a voltage source and a resistor when in a loop exposed to a varying magnetic field. But you only have access to the terminals of the resistor, so when you measure across the terminals you'll get the net voltage: the generated EMF minus the voltage drop due to ohms law.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
Notaros seems to be modeling a similar circuit so that the EMF inducing the current is shown as two lumped voltage sources in the circuit, instead of computing the induced current in the distributed circuit due to the EMF. I kind of understand Notaros wanting to model the EMF into the circuit, but doing so Notaros is actually converting a non-conservative circuit into a conservative one. To me that looks like an illegal chess move (converting a non-conservative circuit into a conservative circuit).
What Notaros did was a math trick, very common in textbooks, but that unfortunately confuses KVLers. They think that if you model some circuit with an equivalent circuit, the components of that equivalent circuit will be found in the modeled circuit.
For instance, this is a very simplified model of a transistor for small signals at low frequencies.
(https://www.researchgate.net/publication/304746021/figure/fig2/AS:379772296286211@1467556179896/The-small-signal-equivalent-circuit-of-the-subthreshold-transistor-taking-into-account.png)
KVLers think that if they open a transistor up they'll find a resistor connected in parallel with a voltage-controlled current source. Well, no. That's just a mathematical trick to help you solve the circuit. A lot of assumptions are implicit in this model. Some of them are in the model name. Signals must be small and frequencies, low, among other things (like, for example, ambient temperature, biasing, etc.)
Notaros modeling gives the same result if he decided to use Faraday's law, however there are a lot of assumptions that he doesn't mention, just as in the transistor model. One of them is that there's no real battery or generator in the path of the circuit.
KVLers can't understand that the battery they are looking for is not in the resistors or the wires. Their explanations always contradict each other. For example. When the loop with two dimensionally small resistors are connected with wires, they say that the voltage is generated in the wires, but not in the resistors. When we eliminate the wires, or when the wires are the resistors themselves, they say that itsy bitsy teeny tiny little batteries suddenly migrate inside the resistors.
What they don't tell you is when exactly these itsy bitsy teeny tiny little batteries migrate from the wires to the resistors. There's no theory to predict that. Search and you'll not find anywhere in the literature about electromagnetism,
Notaros, for example, contradicts the itsy bitsy teeny tiny little battery model, as he put two lumped generators in series with the resistors, although his loop is comprised of two resistive wires and nothing else.
That is exactly the problem: the resistors are both behaving as a voltage source and a resistor when in a loop exposed to a varying magnetic field. But you only have access to the terminals of the resistor, so when you measure across the terminals you'll get the net voltage: the generated EMF minus the voltage drop due to ohms law.
Are you suggesting that if I have for example six resistors with identical resistance but with different physical lengths eg. 0402, 0603, 0805, 1206, and leaded (non-inductive) resistors, I should see different voltages across these resistors due to the different physical sizes because the longer resistors should have getting more EMF than the shorter ones?
Edit: For example if 1206 is three times the length of 0402, the 1206 should be getting three times the EMF?
That is exactly the problem: the resistors are both behaving as a voltage source and a resistor when in a loop exposed to a varying magnetic field. But you only have access to the terminals of the resistor, so when you measure across the terminals you'll get the net voltage: the generated EMF minus the voltage drop due to ohms law.
Are you suggesting that if I have for example six resistors with identical resistance but with different physical lengths eg. 0402, 0603, 0805, 1206, and leaded (non-inductive) resistors, I should see different voltages across these resistors due to the different physical sizes because the longer resistors should have getting more EMF than the shorter ones?
Edit: For example if 1206 is three times the length of 0402, the 1206 should be getting three times the EMF?
Yes, for the resistors placed in a circle as you put then in the figure, the induced voltage is proportional to the length of the resistor, but the voltage drop only depends on the resistance.
That is exactly the problem: the resistors are both behaving as a voltage source and a resistor when in a loop exposed to a varying magnetic field. But you only have access to the terminals of the resistor, so when you measure across the terminals you'll get the net voltage: the generated EMF minus the voltage drop due to ohms law.
Are you suggesting that if I have for example six resistors with identical resistance but with different physical lengths eg. 0402, 0603, 0805, 1206, and leaded (non-inductive) resistors, I should see different voltages across these resistors due to the different physical sizes because the longer resistors should have getting more EMF than the shorter ones?
Edit: For example if 1206 is three times the length of 0402, the 1206 should be getting three times the EMF?
Yes, for the resistors placed in a circle as you put then in the figure, the induced voltage is proportional to the length of the resistor, but the voltage drop only depends on the resistance.
Just to make sure that I understand you correctly: You are saying that if I have six identical 0402 resistors and measure the voltages across these resistors, I should get different voltage values when I have six 1206 resistors with the same resistance as 0402s?
Just to make sure that I understand you correctly: You are saying that if I have six 100 ohm 0402 resistors and measure the voltages across these resistors one at a time, I should get different voltage values when I have six 100 ohm 1206 resistors and repeat the voltage measurement across each resistor?
EDIT: by the way, I have said it many, many times, that the same apply to wires and resistors: under a varying magnetic field, both wires and resistors behave like a voltage source in series with a resistor.
Just to make sure that I understand you correctly: You are saying that if I have six 100 ohm 0402 resistors and measure the voltages across these resistors one at a time, I should get different voltage values when I have six 100 ohm 1206 resistors and repeat the voltage measurement across each resistor?
Bang!
Just to make sure that I understand you correctly: You are saying that if I have six 100 ohm 0402 resistors and measure the voltages across these resistors one at a time, I should get different voltage values when I have six 100 ohm 1206 resistors and repeat the voltage measurement across each resistor?
Bang!
What? Did your brain just exploded? Let me explain with numbers and equations, or as you call it 'mathematical tricks':
In the original Lewin ring, if we assume the resistors are much smaller than the ring we can approximate the voltage across each resistor as
\$I=\frac{1V}{100\Omega+900\Omega}=1mA\$
\$V_1=-1mA.100\Omega=-0.1V\$
\$V_2=1mA.900\Omega=0.9V\$
But now, let us make the 900 ohms resistor much bigger so that it occupies one quarter of the ring. For the 100 ohms resistor we see no change, but now for the 900 resistor we have to subtract the induced EMF in the resistor itself and this is what we can measure across the terminals of the resistor:
\$V_1=1mA.900\Omega-\frac{1V}{4}=0.65V\$
Just to make sure that I understand you correctly: You are saying that if I have six 100 ohm 0402 resistors and measure the voltages across these resistors one at a time, I should get different voltage values when I have six 100 ohm 1206 resistors and repeat the voltage measurement across each resistor?
Bang!
What? Did your brain just exploded? Let me explain with numbers and equations, or as you call it 'mathematical tricks':
In the original Lewin ring, if we assume the resistors are much smaller than the ring we can approximate the voltage across each resistor as
\$I=\frac{1V}{100\Omega+900\Omega}=1mA\$
\$V_1=-1mA.100\Omega=-0.1V\$
\$V_2=1mA.900\Omega=0.9V\$
But now, let us make the 900 ohms resistor much bigger so that it occupies one quarter of the ring. For the 100 ohms resistor we see no change, but now for the 900 resistor we have to subtract the induced EMF in the resistor itself and this is what we can measure across the terminals of the resistor:
\$V_1=1mA.900\Omega-\frac{1V}{4}=0.65V\$
So, the voltage on the load on the secondary of a transformer depends on its size. If I have a resistor, or whatever, that is physically comparable to size of the transformer, the voltage will drop. If I choose a load whose size is much smaller than the dimensions of the loop, I will have a higher voltage.
Wow! Lewin, you son of a gun. You fooled us all.
jesuscf, you really know what you're talking about. Can you teach me electronics? Please!
Self-destruction in 3, 2, 1, electroBOOM!
Classic.
PS: if that was the case, a transformer would never be lumpable.
Shhh, I'm trying to imagine a transformer datasheet. I can see a graph! Load dimensions vs. output voltage!
Ngggghhhh!
Nope. Lost it.
Check the attached pdf from Electromagnetics by Notaros, pages 279-280, example 6.6.
If you don't trust what I said about the circuit equivalent of the resistors in the original one-loop ring, just build it, measure it, and post your results.
If you don't trust what I said about the circuit equivalent of the resistors in the original one-loop ring, just build it, measure it, and post your results.
Look at the video posted by or fellow KVLer, fromjesse
He used big chunky 5W ceramic resistors, one is 150 Ω and the other is 47 Ω, 5% tolerance. The transformer is wound at about 200mV per turn, which gives you 1mA in the loop, and the voltages he measures are exactly what should be: around 150mV and 48 mV, respectively.
Man, I can't get enough of debunking your KVLer claims. And it's so easy since you KVLers provide all the evidence we need to.
For this 900 ohm resistor measurement, I had to be more careful not to pick up an induced voltage in the probing wires, so I used the setup shown in one of the attached pictures.
This Lewin guy must be like one of those aliens from the movie "The Thing". He clearly brainwashed the whole of MIT.
I just found another EM textbook from MIT OCW that has the two resistor rings around a changing flux region... and it agrees with him.
It is also available online for free - surely a way to propagate these... How did Bob Duhamel of RSD Academy call these? Nonstandard concepts that go against the science and engineering establishment? (I'll fetch the exact quote later).
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/about-this-book/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/textbook-contents/
Not only Lewin must have brainwashed this author, but he clearly has a time machine because this textbook was published in 1979, even before Romer's paper. The sneaky little Dutch devil!
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
This Lewin guy must be like one of those aliens from the movie "The Thing". He clearly brainwashed the whole of MIT.
I just found another EM textbook from MIT OCW that has the two resistor rings around a changing flux region... and it agrees with him.
It is also available online for free - surely a way to propagate these... How did Bob Duhamel of RSD Academy call these? Nonstandard concepts that go against the science and engineering establishment? (I'll fetch the exact quote later).
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/about-this-book/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/textbook-contents/
Not only Lewin must have brainwashed this author, but he clearly has a time machine because this textbook was published in 1979, even before Romer's paper. The sneaky little Dutch devil!
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
At this point I am pretty sure you are just delusional.
This Lewin guy must be like one of those aliens from the movie "The Thing". He clearly brainwashed the whole of MIT.
I just found another EM textbook from MIT OCW that has the two resistor rings around a changing flux region... and it agrees with him.
It is also available online for free - surely a way to propagate these... How did Bob Duhamel of RSD Academy call these? Nonstandard concepts that go against the science and engineering establishment? (I'll fetch the exact quote later).
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/about-this-book/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/textbook-contents/
Not only Lewin must have brainwashed this author, but he clearly has a time machine because this textbook was published in 1979, even before Romer's paper. The sneaky little Dutch devil!
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
Obviously another 'bad prober.' ;D
It's clear from Romer's paper that he had a crisis of conscience about KVL - he tells an amusing anecdote when he says he first learned about the non-uniqueness of voltages from Rogers and Shoemaker during an oral exam. I wonder if Lewin had a similar revelation which is why he says "Kirchoff is for the birds and Faraday is not." Unfortunately for Lewin, it also appears his biggest crime was saying "Kirchoff is for the birds, and Faraday is not."
This Lewin guy must be like one of those aliens from the movie "The Thing". He clearly brainwashed the whole of MIT.
I just found another EM textbook from MIT OCW that has the two resistor rings around a changing flux region... and it agrees with him.
It is also available online for free - surely a way to propagate these... How did Bob Duhamel of RSD Academy call these? Nonstandard concepts that go against the science and engineering establishment? (I'll fetch the exact quote later).
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/about-this-book/
https://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/textbook-contents/
Not only Lewin must have brainwashed this author, but he clearly has a time machine because this textbook was published in 1979, even before Romer's paper. The sneaky little Dutch devil!
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
Obviously another 'bad prober.' ;D
It's clear from Romer's paper that he had a crisis of conscience about KVL - he tells an amusing anecdote when he says he first learned about the non-uniqueness of voltages from Rogers and Shoemaker during an oral exam. I wonder if Lewin had a similar revelation which is why he says "Kirchoff is for the birds and Faraday is not." Unfortunately for Lewin, it also appears his biggest crime was saying "Kirchoff is for the birds, and Faraday is not."
Quotehttps://ocw.mit.edu/resources/res-6-002-electromagnetic-field-theory-a-problem-solving-approach-spring-2008/Definitively another guy that doesn't understand that the voltage between nodes VAD depends only on the unique path of the original circuit, a circuit which is not changing shape or moving.
The Zahn-Romer-Lewin ring is in section "6.2.3: Transformer Action", "a) Voltages are not unique" (p. 411)
When measuring, the voltage the instrument displays depends on the path of the instrument wires, but that is not the voltage VAD, it is the voltage at the instrument! With that understanding it is a trivial task to find the correct and unique voltage between nodes VAD which is independent of the path of the instrument wires. So, how do you find the correct voltage between nodes 'A' and 'D', VAD? Using KVL of course!
Regarding the "tiny voltage sources", the funny thing (which is a bit sad also) is that all the "experimental proof" by Jesse and e.g. Cyriel Mabilde are just cunning demonstrations of how to create paths that enclose a variable amount of magnetic flux. The sad part is that they're unable to see it and will keep claiming it is proof of "KVL holds". But in reality they're not measuring a gradual voltage build-up in the "Lewin Ring", but just the EMF induced in their measurement loop. This under the condition that there is only negligible current flowing through the ring and the measurement loop, of course.
For this 900 ohm resistor measurement, I had to be more careful not to pick up an induced voltage in the probing wires, so I used the setup shown in one of the attached pictures.
Cool! That's what I thought. Jesse measured the wrong voltage. He let his probes pick up induced voltage.
Thank you, jesuscf. We finally managed to show that Jesse's experiments are a hoax.My experiment is not a hoax. The reason you couldn't see my experiment in my garage is because you were in your mums basement at the time :-DD :-DD :-DD.
No wonder he left the discussion. He knew he would be caught and exposed sooner or later by your imaginative intellect.I didn't leave the discussion, unlike you, I don't live in my mom's basement so I have to work and I have friends and family to interact with so I can't be arguing on here every day.
Of course. The MIT is notoriously known for its scarcely prepared professors of physics and engineering.
Here is yet another professor who does not understand the basics of electromagnetism!
Shame on you, MIT!!!
Listen to the guys in a garage, instead. They have an oscilloscope, so they clearly know what they are talking about.
Lumped circuits are obtained by connecting lumped elements. Typical
lumped elements are resistors, capacitors, inductors, and transformers.
We have encountered them in the laboratory, and we can see them in our
radio sets. The key property associated with lumped elements is their
small size (compared to the wavelength corresponding to their normal
frequency of operation.) From the more general electromagnetic field point
of view, lumped elements are point singularities; that is, they have negligible
physical dimensions. In this way they are similar to a particle.
Lumped elements may have two terminals, as in a resistor, or more than
two terminals, as in a transformer or transistor. For two-terminal
lumped elements, it can be shown that the general laws governing the
electromagnetic field, together with the restriction on physical size indicated
above, imply that at all times the current entering one terminal is
equal to the current leaving the other terminal, and that the voltage difference
between the two terminals can be unambiguously defined by physical
measurements. Thus, for two-terminal lumped elements, the current
through the element and the voltage across it are well-defined quantities. For
lumped elements with more than two terminals, the current entering any
terminal and the voltage across any pair of terminals are well defined at all times.
For the remainder of this book, any interconnection of the lumped
elements such that the dimensions of the circuit are small compared with the
wavelength associated with the highest frequency of interest will be called
a lumped circuit.
As long as this restriction on the size of the circuit holds, Kirchhoff's
current and voltage laws (to be discussed in Secs. 3 and 4) are valid. This
restriction is a consequence of the fact that Kirchhoff's laws are approximations
of Maxwell's celebrated equations, which are the general laws
of the electromagnetic field. The approximation is analogous to the fact
that Newton's laws of classical mechanics are approximations to the laws
of relativistic mechanics. Even though they are approximations, the laws
of Newton and Kirchhoff can be applied to a large number of practical
Nonsense. I practiced safe probing, and KVL works. Welcome to the real world kiddo :-DD :-DD :-DD.
Let the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Nonsense. I practiced safe probing, and KVL works. Welcome to the real world kiddo :-DD :-DD :-DD."Safe probing" is for the weak. Real men measure the "interference".
For this 900 ohm resistor measurement, I had to be more careful not to pick up an induced voltage in the probing wires, so I used the setup shown in one of the attached pictures.
Cool! That's what I thought. Jesse measured the wrong voltage. He let his probes pick up induced voltage.
Thank you, jesuscf. We finally managed to show that Jesse's experiments are a hoax. No wonder he left the discussion. He knew he would be caught and exposed sooner or later by your imaginative intellect.
If you don't trust what I said about the circuit equivalent of the resistors in the original one-loop ring, just build it, measure it, and post your results.
Look at the video posted by your fellow KVLer, fromjesse
https://www.youtube.com/watch?v=iDWv8QJrzUo&t=23 (https://www.youtube.com/watch?v=iDWv8QJrzUo&t=23)
He used big chunky 5W ceramic resistors, one is 150 Ω and the other is 47 Ω, 5% tolerance. The transformer is wound at about 200mV per turn, which gives you 1mA in the loop, and the voltages he measures are exactly what should be: around 150mV and 48 mV, respectively.
Man, I can't get enough of debunking your KVLer claims. And it's so easy since you KVLers provide all the evidence we need to.
For this 900 ohm resistor measurement, I had to be more careful not to pick up an induced voltage in the probing wires, so I used the setup shown in one of the attached pictures.
Cool! That's what I thought. Jesse measured the wrong voltage. He let his probes pick up induced voltage.
Thank you, jesuscf. We finally managed to show that Jesse's experiments are a hoax. No wonder he left the discussion. He knew he would be caught and exposed sooner or later by your imaginative intellect.
Since this thread has sprung back to live, let me share some information to further demolish team's Lewin position. Check out this marvelous quote from an old book:QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Where that quote comes from? From this book: A Treatise On Electricity and Magnetism by James Clerk Maxwell (page 418, Dover edition from 1954 based in third edition published in 1891)! So, should we treat the EMF due to electromagnetic induction differently from the point of view of KVL to any other EMF? I think Maxwell is telling us 'no' way back in time from 1873 when he wrote the book! If you continue reading, the rest of the explanation looks pretty much like KVL and KCL to me, which he introduced earlier in the same book starting in page 406.
Ah, good, the "Treatise".
Are we going to bring back ether, as well?
And yes, the EMF due to induction is a very special kind of EMF.
All the other ones fall into the circulation integral.
You are still stuck at the difference between KVL and extended KVL?
Oh, dear.
Wanna see how I can treat induction EMF as any other EMF?
Simple, I localize it, just like with lumped circuits with inductors, transformers, motors...
You're still stuck there?
It's written on Hayt's book, the one you quoted three or four years ago.
Ah, good, the "Treatise".
Are we going to bring back ether, as well?
And yes, the EMF due to induction is a very special kind of EMF.
All the other ones fall into the circulation integral.
And, Jesse, when I say "listen to the guys in a garage" I am not comparing them to me, but to the university professors who wrote books and papers where this problem was carefully analyzed.
Purcell, Morin, Roche, Ramo, Whinnery, VanDuzer, Romer, Rosser, Zahn, Haus, Melcher, Nicholson, Brandao Faria, ...
Since this thread has sprung back to live, let me share some information to further demolish team's Lewin position. Check out this marvelous quote from an old book:QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Where that quote comes from? From this book: A Treatise On Electricity and Magnetism by James Clerk Maxwell (page 418, Dover edition from 1954 based in third edition published in 1891)! So, should we treat the EMF due to electromagnetic induction differently from the point of view of KVL to any other EMF? I think Maxwell is telling us 'no' way back in time from 1873 when he wrote the book! If you continue reading, the rest of the explanation looks pretty much like KVL and KCL to me, which he introduced earlier in the same book starting in page 406.
Indeed. And why wouldn't he? It makes sense. Doing otherwise makes no sense.
There's just no logical reason for Team Lewin to keep on going.
If an element is small compared to the wavelength, and the current going in one terminal equals the that going out the other, and the voltage can be physically unambiguously physically defined by measurement, then there's no reason KVL doesn't hold.
Btw, great job on the mini Lewin Ring setup!
I see you edited you message.I try not to make an excessive number of posts.
Since I noticed that you just dump references without reading and/or understanding them, and that you also quite often just lie, allow me to check a couple of these references:page 358
Electricity and Magnetism by Purcell E.M., Morin D.J:
They have Problem 7.4 similar to Lewin's problem. No solution to the problem given! The problem asks "What will each voltmeter read?" but it is not asking what is the voltage between nodes A and D! I have the impression that the problem wants to point out that you have to be careful when you measure voltages and the instrument probes are under the effect of an external varying magnetic field...
Fields and Waves in Communication Electronics by Simon Ramo, John R. Whinnery, Theodore Van Duzer:
At the beginning of chapter 4 they say this: "Kirchhoff's two laws provide the basis for classical circuit theory. We begin with the voltage law as a way of reviewing the basic element values of lumped-circuit theory. The law states that for any closed loop of a circuit, the algebraic sum of voltages for the individual branches is zero... the basis for this is Faraday's law for a closed path, written as..." And then, they proceed to use KVL with induced EMFs to solve a bunch of stuff. How is that supposed to support your position?
I see you edited you message.I try not to make an excessive number of posts.QuoteSince I noticed that you just dump references without reading and/or understanding them, and that you also quite often just lie, allow me to check a couple of these references:page 358
Electricity and Magnetism by Purcell E.M., Morin D.J:
They have Problem 7.4 similar to Lewin's problem. No solution to the problem given! The problem asks "What will each voltmeter read?" but it is not asking what is the voltage between nodes A and D! I have the impression that the problem wants to point out that you have to be careful when you measure voltages and the instrument probes are under the effect of an external varying magnetic field...
(http://link: [url=https://i.postimg.cc/kGXzD9jR/purcell-faraday-2.jpg]https://i.postimg.cc/kGXzD9jR/purcell-faraday-2.jpg[/url])
A little excerpt (bold mine) which some have difficulty in understanding:
"...Kirchhoff Loop rule is no longer valid"
I wonder what that could mean... Why, oh why couldn't they be any clearer???
But let's see the solution of the problem on page 710 (again, bold mine)
"The moral of this problem is that if a setup contains changing flux, it makes no sense to talk about the voltage difference (that is, the value of −integral of E·ds) between two points. It is necessary to state the path over which −integral of E · ds is calculated."
Still of the opinion it does not support my position, which is that KVL is no longer valid and voltage depends on path?
:palm:QuoteFields and Waves in Communication Electronics by Simon Ramo, John R. Whinnery, Theodore Van Duzer:
At the beginning of chapter 4 they say this: "Kirchhoff's two laws provide the basis for classical circuit theory. We begin with the voltage law as a way of reviewing the basic element values of lumped-circuit theory. The law states that for any closed loop of a circuit, the algebraic sum of voltages for the individual branches is zero... the basis for this is Faraday's law for a closed path, written as..." And then, they proceed to use KVL with induced EMFs to solve a bunch of stuff. How is that supposed to support your position?
I'll show you how. Page 174 of the third edition
"let us take a closed integral of electric field along the conductor of the coil, returning by the path across the terminals. Since the contribution along the part of the path which follows the conductor is zero, all the voltage appears ACROSS the terminals."
I'll translate this for you: voltage ALONG the filament of the coil = 0; voltage ACROSS the terminals = V not zero.
KVL cannot survive two values of voltage between the same two points. Unless you use a trick and pretend that there is only one voltage, that ACROSS the coil, and pretend its a potential difference.
Read page 179
"In the above we seem to be treating voltage as potential difference when we take voltage of a node with respect to the chosen reference, but note that this is only after the circuit is defined and we are only breaking up the integral of E.dl into its contributions over the various branches. As illustrated in the preceding section, we do have to define the path carefully whenever there are inductances or other elements with contribution to voltage from Faraday's law."
But hey, and this is related to the above, have you noticed that Jesse is repeatedly posting the same image of a circuit with a transformer, two outputs on a circuit with resistors and a lot of voltmeters? Suppose one turn around the core gives you an emf of 1V.
Can you place the values of your "path independent voltage" inside all those voltmeters? Because I have a hunch you cannot do it, using the voltage that according to you builds up in the coil.
I can easily do it using my definition of voltage, in accordance with Purcell, Ramo etc, Haus etc, Brandao Faria, Zahn, etc... but I wonder if you have any idea of what 'your voltage' (or the 'McDonald voltage', if you prefer to call it that way) is, in that context.
(Pretty sure Jesse doesn't know either, because I've asked and he refused to answer)
Edit: further clarifies what "voltage" I want you to place inside those voltmeters.
I will place the values of "my" path dependent voltage once either you or Jesse post your solution.
A consequence of Faraday’s law of induction is that Kirchhoff’s loop rule (which states that \$\int_{}^{}E.ds=0\$ around a closed path) is no longer valid in situations where there is a changing magnetic field. Faraday has taken us beyond the comfortable realm of conservative electric fields.
Let the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Since this thread has sprung back to live, let me share some information to further demolish team's Lewin position.
Since this thread has sprung back to live, let me share some information to further demolish team's Lewin position.
Aaww, the cute little KVLey demolished the argument of the big bad Lewin-Newey. Poor Lewin-Newey.
Once again Purcel, the same as Hayt, is progressing through the subject in a sequential historical way when he writes:QuoteA consequence of Faraday’s law of induction is that Kirchhoff’s loop rule (which states that \$\int_{}^{}E.ds=0\$ around a closed path) is no longer valid in situations where there is a changing magnetic field. Faraday has taken us beyond the comfortable realm of conservative electric fields.
If we take that in a different context,
it will directly contradict what Maxwell says:QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
As for the second quote:
"let us take a closed integral of electric field along the conductor of the coil, returning by the path across the terminals. Since the contribution along the part of the path which follows the conductor is zero, all the voltage appears ACROSS the terminals."
That is ABSOLUTELY incorrect as the induced voltage is distributed through the conductor as many experiments have demonstrated.
EDIT: You may also want to check page 199 of Fields and Waves in Communication Electronics where they explicitly contradict the statement above by considering the effect of the electric field between the turns of the inductor!
QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Apart from the fact that Maxwell is simply enumerating the EMF available at the time: electrochemical piles/electrostatic machines, thermopiles and em induction (remember, if you consider localized sources you can apply what today we call "extended KVL") - what if it actually contradicted Maxwell?
Maxwell believed in the existence of the luminiferous ether. He was wrong.
What we today call "Maxwell's equations" is the result of the work of Heaviside, using the notation expressed in the treatise would be maddening. Expliciting all gradients, curls, divergences...
A lot of thing has changed since 1865.
QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Apart from the fact that Maxwell is simply enumerating the EMF available at the time: electrochemical piles/electrostatic machines, thermopiles and em induction (remember, if you consider localized sources you can apply what today we call "extended KVL") - what if it actually contradicted Maxwell?
Maxwell believed in the existence of the luminiferous ether. He was wrong.
What we today call "Maxwell's equations" is the result of the work of Heaviside, using the notation expressed in the treatise would be maddening. Expliciting all gradients, curls, divergences...
A lot of thing has changed since 1865.
But one thing that has not changed since the time of Maxwell is that KVL explicitly includes electromagnetic induction EMFs which are not to be treated differently from any other EMFs, "whatever be the origin of the force"!
QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Apart from the fact that Maxwell is simply enumerating the EMF available at the time: electrochemical piles/electrostatic machines, thermopiles and em induction (remember, if you consider localized sources you can apply what today we call "extended KVL") - what if it actually contradicted Maxwell?
Maxwell believed in the existence of the luminiferous ether. He was wrong.
What we today call "Maxwell's equations" is the result of the work of Heaviside, using the notation expressed in the treatise would be maddening. Expliciting all gradients, curls, divergences...
A lot of thing has changed since 1865.
But one thing that has not changed since the time of Maxwell is that KVL explicitly includes electromagnetic induction EMFs which are not to be treated differently from any other EMFs, "whatever be the origin of the force"!
If the induced EMF is not in the path of the circuit, yes, you can include it in KVL. If not, KVL fails.
You don't even now what is KVL!
You don't even now what is KVL!
KVL is a special case of Faraday's law when you don't have a time-varying magnetic field in the surface enclosed by the path of the circuit.
Your ignorance is laughable! :-DD
And, Jesse, when I say "listen to the guys in a garage" I am not comparing them to me, but to the university professors who wrote books and papers where this problem was carefully analyzed.
Purcell, Morin, Roche, Ramo, Whinnery, VanDuzer, Romer, Rosser, Zahn, Haus, Melcher, Nicholson, Brandao Faria, ...
have you noticed that Jesse is repeatedly posting the same image of a circuit with a transformer, two outputs on a circuit with resistors and a lot of voltmeters? Suppose one turn around the core gives you an emf of 1V.
Can you place the values of your "path independent voltage" inside all those voltmeters?
Lumped circuits are obtained by connecting lumped elements. Typical
lumped elements are resistors, capacitors, inductors, and transformers.
We have encountered them in the laboratory, and we can see them in our
radio sets. The key property associated with lumped elements is their
small size (compared to the wavelength corresponding to their normal
frequency of operation.) From the more general electromagnetic field point
of view, lumped elements are point singularities; that is, they have negligible
physical dimensions. In this way they are similar to a particle.
Lumped elements may have two terminals, as in a resistor, or more than
two terminals, as in a transformer or transistor. For two-terminal
lumped elements, it can be shown that the general laws governing the
electromagnetic field, together with the restriction on physical size indicated
above, imply that at all times the current entering one terminal is
equal to the current leaving the other terminal, and that the voltage difference
between the two terminals can be unambiguously defined by physical
measurements. Thus, for two-terminal lumped elements, the current
through the element and the voltage across it are well-defined quantities. For
lumped elements with more than two terminals, the current entering any
terminal and the voltage across any pair of terminals are well defined at all times.
For the remainder of this book, any interconnection of the lumped
elements such that the dimensions of the circuit are small compared with the
wavelength associated with the highest frequency of interest will be called
a lumped circuit.
As long as this restriction on the size of the circuit holds, Kirchhoff's
current and voltage laws (to be discussed in Secs. 3 and 4) are valid. This
restriction is a consequence of the fact that Kirchhoff's laws are approximations
of Maxwell's celebrated equations, which are the general laws
of the electromagnetic field. The approximation is analogous to the fact
that Newton's laws of classical mechanics are approximations to the laws
of relativistic mechanics. Even though they are approximations, the laws
of Newton and Kirchhoff can be applied to a large number of practical
(Pretty sure Jesse doesn't know either, because I've asked and he refused to answer)
If the induced EMF is not in the path of the circuit, yes, you can include it in KVL. If not, KVL fails.
QuoteLet the components of the electromotive intensity be X, Y, Z.
The electromotive intensity at any point is the resultant force on a unit of positive electricity placed at that point. It may arise (1) from electrostatic action, in which case if V is the potential,
\$X=-\frac{dV}{dx},Y=-\frac{dV}{dy},Z=-\frac{dV}{dz}; (1)\$
or (2) from electromagnetic induction, the laws of which we shall afterwards examine; or (3) from thermoelectric or electrochemical action at the point itself, tending to produce a current in a given direction.
We shall in general suppose that X, Y, Z represent the components of the actual electromotive intensity at the point, whatever be the origin of the force, but we shall occasionally examine the result of supposing it entirely due to variation of potential.
Apart from the fact that Maxwell is simply enumerating the EMF available at the time: electrochemical piles/electrostatic machines, thermopiles and em induction (remember, if you consider localized sources you can apply what today we call "extended KVL") - what if it actually contradicted Maxwell?
Maxwell believed in the existence of the luminiferous ether. He was wrong.
What we today call "Maxwell's equations" is the result of the work of Heaviside, using the notation expressed in the treatise would be maddening. Expliciting all gradients, curls, divergences...
A lot of thing has changed since 1865.
But one thing that has not changed since the time of Maxwell is that KVL explicitly includes electromagnetic induction EMFs which are not to be treated differently from any other EMFs, "whatever be the origin of the force"!
But no, Lewin defines reality and we're supposed to ignore the others.
I think what you mean to say is that IF there is UNDOCUMENTED EMF across any part of the loop, then KVL fails.
I'm pretty sure Team Lewin doesn't even know what they are arguing for, much less what they are arguing about.
But what baffles me is Team Lewin's refusal to draw a definitive line in reasoning and say "Here's where you're wrong. (Insert reason)" ("You" being Team KVL.)
The only thing they really seem certain of is that Lewin cannot be wrong. Maybe former students? Maybe fellow Dutchmen? I've read that the Dutch are both very loyal to their own as well as very tenacious in negotiations with others.
Team Lewin also seems to ignore the fact that some PhD Physics Professors also disagree with them -- it doesn't take a genius to see that not all PhD Physics Professors agree on the topic so there must be room for discussion..
But no, Lewin defines reality and we're supposed to ignore the others.
It is waste to argue with true believers because they simply ignore anything that does not support their beliefs.
have you noticed that Jesse is repeatedly posting the same image of a circuit with a transformer, two outputs on a circuit with resistors and a lot of voltmeters? Suppose one turn around the core gives you an emf of 1V.
Can you place the values of your "path independent voltage" inside all those voltmeters?
What does that even mean?
And according to Team Lewin's fully endorsed top of the line textbook, transformer windings are completely acceptable:Quote from: Desoer-Kuh
Lumped circuits are obtained by connecting lumped elements.
Quote(Pretty sure Jesse doesn't know either, because I've asked and he refused to answer)
If I refused to answer any of your questions it was for one of two reasons: 1: It was incoherent or unambiguous words which did not actually form an unambiguous question.
Or 2: At some point I realized you were just throwing muddy questions at the wall in hopes one would stick while refusing to answer a single one of mine so I began question bargaining which meant I had to refuse to answer questions just to get you to answer a couple of mine. Doesn't mean I didn't know the answers though.
And you still have not answered MY question as I asked it.
Question: In the following diagram, in a real life physical lab test performed with real (time synchronized) volt meters with a real transformer and real resistors CONNECTED AS SHOWN, will the readings of all the volt meters sum to zero, within the accuracy and resolution limitations of the volt meters? YES or NO.
(Or if you believe SOMETIMES is the answer, then answer SOMETIMES and explain one scenario for a YES condition and one scenario for a NO condition WITH THE VOLT METERS AND ALL COMPONENTS CONNECTED AS SHOWN - Running additional conductors through the transformer core is not allowed - nor is removing existing conductors from through the transformer core!)
(https://i.postimg.cc/jdJntBXT/20211128-121506.jpg)
But what baffles me is Team Lewin's refusal to draw a definitive line in reasoning and say "Here's where you're wrong. (Insert reason)" ("You" being Team KVL.)
The only thing they really seem certain of is that Lewin cannot be wrong. Maybe former students? Maybe fellow Dutchmen? I've read that the Dutch are both very loyal to their own as well as very tenacious in negotiations with others.
At the very least I'd have expected Team Lewin to say "Yes, the volt meters in your diagram will sum to zero, and KVL does appear to work, but due to a certain technicality of a certain definition, we say KVL isn't holding.."
But we can't even get that much from them, which means they don't even understand the topic much less what they are arguing for.
Team Lewin also seems to ignore the fact that some PhD Physics Professors also disagree with them -- it doesn't take a genius to see that not all PhD Physics Professors agree on the topic so there must be room for discussion.. But no, Lewin defines reality and we're supposed to ignore the others.
Lewin is just one of many, many, many other professors who know how to correctly apply classical electrodynamics. What we (well, I at least) call the Romer-Lewin ring is mentioned in a 1969 teaser by Moorcroft, followed by a discussion published the year after
Lewin is just one of many, many, many other professors who know how to correctly apply classical electrodynamics. What we (well, I at least) call the Romer-Lewin ring is mentioned in a 1969 teaser by Moorcroft, followed by a discussion published the year afterSredni (the king of cherry picking!), have you calculated the voltage between nodes A and D, VAD yet? Have you figured what is the difference between the voltage between two nodes and the voltage measured by a 'voltmeter'?
Lewin, and team Lewin by that matter, are so wrong that they even disagree with what Maxwell explicitly says.
Let start with definition of KVL as stated by Maxwell in "A Treatise on Electricity & Magnetism" from 1873:
[Page 406 article 282b]
The theory of conjugate conductors has been investigated by Kirchhoff, who has stated the conditions of a linear system in the following manner, in which the consideration of the potential is avoided.
(1) (Condition of 'continuity.') At any point of the system the sum of all the currents which flow towards that point is zero.
(2) In any complete circuit formed by the conductors the sum of the electromotive forces taken round the circuit
Yes I did, and for several paths.
The fact that you either did not understand that, or just simply revert back to factory defaults and keep asking the same questions again and again because you don't like the answer is irrelevant.
Maxwell believed in the luminiferous ether.
Do you believe in the luminiferouts ether?
(Or should I ask "do you know what the luminiferous ether is"?)
I am not a native English speaker. Could you please enlighten me about what "taken round the circuit" means in English?
Yes I did, and for several paths.
The fact that you either did not understand that, or just simply revert back to factory defaults and keep asking the same questions again and again because you don't like the answer is irrelevant.
When you calculate the voltage VAD, there is only one path, the path of the ring circuit, which is neither changing nor moving!
Maxwell believed in the luminiferous ether.
Do you believe in the luminiferouts ether?
(Or should I ask "do you know what the luminiferous ether is"?)
And here you are! Denigrating Maxwell as predicted.
Also, I am pretty sure Maxwell contemplated the possibility of a "luminiferous ether", but he was not sold on it unless solid evidence of it was provided. (I think I read that somewhere in one of his writings...)
I am not a native English speaker. Could you please enlighten me about what "taken round the circuit" means in English?You need to imagine as if Sean Connery is reading the writings of Maxwell! It may make more sense to you then! :-DD
Yes I did, and for several paths.
The fact that you either did not understand that, or just simply revert back to factory defaults and keep asking the same questions again and again because you don't like the answer is irrelevant.
When you calculate the voltage VAD, there is only one path, the path of the ring circuit, which is neither changing nor moving!
Of course you mean the path on the right (A ---> R1 ---> D)?
Or the one on the left (A ---> R2 ---> D)?
Or the one along an imaginary line that splits the circular circuit in half? And if the circuit is not symmetric?
Now paths do not exists because the circuit is stationary
Every day something new.
Maxwell believed in the luminiferous ether.
Do you believe in the luminiferouts ether?
(Or should I ask "do you know what the luminiferous ether is"?)
And here you are! Denigrating Maxwell as predicted.
Not denigrating. Just stating a fact.
Newton believed time and space were absolutes. Is this denigrating Newton?
I am not a native English speaker. Could you please enlighten me about what "taken round the circuit" means in English?QuoteYou need to imagine as if Sean Connery is reading the writings of Maxwell! It may make more sense to you then! :-DD
Yeah, like Jesse, you can't answer and just try to deflect.
Really? So why is relevant to this discussion whether or not Maxwell believed in the "luminiferous ether" or not? You are guilty here of not just one, but two fallacies: denigration and deflection.Not denigrating. Just stating a fact.Maxwell believed in the luminiferous ether.And here you are! Denigrating Maxwell as predicted.
Do you believe in the luminiferouts ether?
(Or should I ask "do you know what the luminiferous ether is"?)
Newton believed time and space were absolutes. Is this denigrating Newton?
You are the one who believe Maxwell is infallible and his Treatise is gospel. I simply pointed out that the Treatise reflects the time it was written. A time where Maxwell's equations as we know them were yet to be penned. A time where people, including Maxwell, believed in the luminiferous ether. You have quoted a passage of the Treatise where Maxwell is illustrating the sources of emf as known at the time, so what? He states explicitly:
"In any complete circuit formed by the conductors the sum of the electromotive forces taken round the circuit..."
And I am wondering: if the emf is a scalar value that results from computing the path integral of that one closed loop (as that little circle implies), why is Maxwell using the plural? You said it yourself: there is only one loop [note], so there must be only one value for the integral computed along that one loop.
I tell you why he is using the plural.
Because in that sentence he was considering the lumped emfs encountered by going around the circuit. That is what KVL was about at the time (and still is now, since its generalization outside of garages is known as Faraday's law).
note I also wonder... what if the circuit has more than one loop linking dB/dt... What single one loop would you choose to compute the one and only value of Vad?
3. you don't know how to answer.
I see that you have banned ano]ther user on your YT channel.
(https://i.postimg.cc/KjvfpC5f/screenshot.png)
https://i.postimg.cc/KjvfpC5f/screenshot.png
I wonder why you do that. :-//
They do not even understand what Belcher and McDonald say, they only get a few sentences here and there.
It takes several years of painstaking study to master a minimal understanding of it.
You can clearly see that they do not have the appropriate background to sustain an argument. The idea of a non-conservative field, which is key to understanding the path dependency of voltage, is foreign to them. Their understanding of the vectorial nature of the electric and magnetic fields, if existent, is precarious, to say the least.
As Dr.Lewin ignores emf literally in half of his circuit stating that voltage on two wires A1-A2 and D1-D2 is 0V,
let's remove both from circuit completely. What we have left are two resistors. Let's take 10 Ohm wire and make full turn out of it, connect tiny 100 Ohms resistor as load. What we have in result - transformer with lossy secondary and load. Voltages on both equal obviously.
It would be rather stupid to measure current through 100 Ohms load, then knowing internal resistance (10 Ohms) of transformer secondary, apply ohms law to calculate voltage :D But wait... this is what Dr.Lewin effectively does in his video "Kirchhoff's Loop Rule Is For The Birds".
Faraday's Law Example 4 (Electromagnetic Induction)
https://www.youtube.com/watch?v=sAsxEBkaty8 (https://www.youtube.com/watch?v=sAsxEBkaty8)
This is the fourth of four examples of the application of Faraday's Law. A current is ramped in a solenoid to produce circles of electric field intensity around the solenoid. The solenoid is surrounded by a conducting ring where the left half of the ring has a higher conductivity than the right half of the ring. What is observed is charge buildup at the boundaries between the two materials.
You are the one who believe Maxwell is infallible and his Treatise is gospel. I simply pointed out that the Treatise reflects the time it was written. A time where Maxwell's equations as we know them were yet to be penned. A time where people, including Maxwell, believed in the luminiferous ether. You have quoted a passage of the Treatise where Maxwell is illustrating the sources of emf as known at the time, so what? He states explicitly:
Interesting. Maxwell is fallible, but Lewin, whom struggles to solve the simplest of circuits, is infallible them!
Also, according to Maxwell (and he says it explicitly) Faraday's law is NOT a generalization of KVL. "Electromagnetic induction, the laws of which we shall afterwards examine" is just one more EMF that must be added to other EMFs when using KVL, "whatever be the origin of the force".
So, according to your logic in Lewin's ring, the wire on the top has half the induced EMF and the wire at the bottom has half the induced EMF. So, can you now can compute the voltage VAD?
note I also wonder... what if the circuit has more than one loop linking dB/dt... What single one loop would you choose to compute the one and only value of Vad?
Then you use KVL and KCL to the complete and correct circuit to compute...
Wanna see another professor doing the same as Belcher, and Lewin? Micheal Melloch of Purdue University - the same Micheal Melloch whose videos Jesse Gordon has linked in the comments of his videos on Lewin's ring. Too bad he is doing what Lewin (and Belcher!) is doing:QuoteFaraday's Law Example 4 (Electromagnetic Induction)
https://www.youtube.com/watch?v=sAsxEBkaty8 (https://www.youtube.com/watch?v=sAsxEBkaty8)
This is the fourth of four examples of the application of Faraday's Law. A current is ramped in a solenoid to produce circles of electric field intensity around the solenoid. The solenoid is surrounded by a conducting ring where the left half of the ring has a higher conductivity than the right half of the ring. What is observed is charge buildup at the boundaries between the two materials.
The charge buildup at the boundaries between the materials is what you KVLers are unable to see.
It's like glass for birds, or storks.
Wanna see another professor doing the same as Belcher, and Lewin? Micheal Melloch of Purdue University - the same Micheal Melloch whose videos Jesse Gordon has linked in the comments of his videos on Lewin's ring. Too bad he is doing what Lewin (and Belcher!) is doing:QuoteFaraday's Law Example 4 (Electromagnetic Induction)
https://www.youtube.com/watch?v=sAsxEBkaty8 (https://www.youtube.com/watch?v=sAsxEBkaty8)
This is the fourth of four examples of the application of Faraday's Law. A current is ramped in a solenoid to produce circles of electric field intensity around the solenoid. The solenoid is surrounded by a conducting ring where the left half of the ring has a higher conductivity than the right half of the ring. What is observed is charge buildup at the boundaries between the two materials.
The charge buildup at the boundaries between the materials is what you KVLers are unable to see.
It's like glass for birds, or storks.
Excellent, I was waiting for something like this. Now, here is a question for you: what would happen if you replace the resistors with capacitors. Say, instead of the 100 ohm resistor place a 100nF capacitor, and instead of the 900 ohm resistor place a 10nF capacitor. What would be the voltage between nodes A and D, VAD at steady state? Spoiler alert: I did that experiment a few weeks ago and it looks very, very bad for team Lewin!
The pretty much cancel each other in the conductor leaving an almost zero net electric field inside.
QuoteThen you use KVL and KCL to the complete and correct circuit to compute...
Sure, you use KVL to prove KVL.
But at this point in time they can base their view of classical electrodynamics on about 150 years of careful refinement by some of the most brilliant minds of the whole planet. So, I'll take that above what Maxwell (which was an absolute genius, but was also pioneering a new field) had to say in 1865. The ether is one glaring example.
A more refined view of classical electrodynamics in a less glaring one, and in fact...
In his Treatise, Maxwell had built his theory around the vector and scalar potentials A and Ψ. They did not locate the energy correctly, however, and Heaviside regarded them as quite distant from the real workings of the field. He proceeded to work back from his energy-flow formula to find a new set of basic equations, equivalent to those in Maxwell’s Treatise but based directly on E and H and so better suited to treating energy flow. By combining two of Maxwell’s expressions relating the vector potential A to the fields E and H, Heaviside derived what he called the “second circuital law,” which related the curl of E directly to the rate of change of H—a fitting partner, he said, for Maxwell’s “first circuital law” relating the curl of H to E and its rate of change (see the box on page 53). By combining them with Maxwell’s expressions for the divergence of the electric displacement D and the magnetic induction B, Heaviside arrived at the compact set of four vector relations we now know as Maxwell’s equations.https://physicstoday.scitation.org/doi/10.1063/PT.3.1788
The pretty much cancel each other in the conductor leaving an almost zero net electric field inside.
Right there is where you are wrong! In Lewin's ring the the induced emf is evenly distributed in the conductors and resistors. He failed to include that emf in the equivalent circuit, that is why he incorrectly concluded that KVL doesn't work.
Wanna see another professor doing the same as Belcher, and Lewin? Micheal Melloch of Purdue University - the same Micheal Melloch whose videos Jesse Gordon has linked in the comments of his videos on Lewin's ring. Too bad he is doing what Lewin (and Belcher!) is doing:QuoteFaraday's Law Example 4 (Electromagnetic Induction)
https://www.youtube.com/watch?v=sAsxEBkaty8 (https://www.youtube.com/watch?v=sAsxEBkaty8)
This is the fourth of four examples of the application of Faraday's Law. A current is ramped in a solenoid to produce circles of electric field intensity around the solenoid. The solenoid is surrounded by a conducting ring where the left half of the ring has a higher conductivity than the right half of the ring. What is observed is charge buildup at the boundaries between the two materials.
The charge buildup at the boundaries between the materials is what you KVLers are unable to see.
It's like glass for birds, or storks.
Excellent, I was waiting for something like this. Now, here is a question for you: what would happen if you replace the resistors with capacitors. Say, instead of the 100 ohm resistor place a 100nF capacitor, and instead of the 900 ohm resistor place a 10nF capacitor. What would be the voltage between nodes A and D, VAD at steady state? Spoiler alert: I did that experiment a few weeks ago and it looks very, very bad for team Lewin!
This is another common trait of believers: once they are cornered that change the topics to something new, so that the debunking has to start from scratch and they can bask in the illusion that this time they could be right.
First is the ring with two resistors joined by conductors. Then the ring with two resistors and a battery. Then the ring with two resistors without conductors in between. Then the uniform resistive ring. Then the perfectly conducting ring. I have seen in the other thread the ring with a transitor in the loop. Now it's the two capacitors in a loop. What is next? A Josephson junction?
Two capacitors in a loop can lead to some nasty paradoxes. Will this invalidate the easily explained ring of just two resistors? Logic dictates that no, it won't. But believers are renowned for not being very good in applying logic.
The pretty much cancel each other in the conductor leaving an almost zero net electric field inside.
Right there is where you are wrong! In Lewin's ring the the induced emf is evenly distributed in the conductors and resistors. He failed to include that emf in the equivalent circuit, that is why he incorrectly concluded that KVL doesn't work.
So... is Belcher wrong?
(https://i.postimg.cc/SRnyVCmR/screenshot.png)
Source: Belcher's note available on Electroboom's channel
Because he too gets (basically) zero net field in the copper wires.
But at this point in time they can base their view of classical electrodynamics on about 150 years of careful refinement by some of the most brilliant minds of the whole planet. So, I'll take that above what Maxwell (which was an absolute genius, but was also pioneering a new field) had to say in 1865. The ether is one glaring example.
A more refined view of classical electrodynamics in a less glaring one, and in fact...
Even in the context of Maxwell's work, there were things corrected in the decades following his treatise by Oliver Heaviside,
Maybe for you. Hence the importance of a formal education,
where with the proper guidance not only the correct knowledge is acquired in a timely manner,
but the BS that characterizes team Lewin is weeded out.
Very well genius: explain what is it a non-conservative field, in the context of Lewin's ring!
QuoteVery well genius: explain what is it a non-conservative field, in the context of Lewin's ring!
...you wouldn't be asking me to explain to you what a non-conservative field is.
That is where you are massively wrong. If your theory is correct it must predict what happens when you change something in the experiment, and that prediction must perfectly match experimental results. That is what KVL does every single time!!! So go ahead, make your prediction!
So, according to your logic in Lewin's ring, the wire on the top has half the induced EMF and the wire at the bottom has half the induced EMF. So, can you now can compute the voltage VAD?
There is the EMF contribution of Eind, but there is also the scalar potential contribution of Ecoul. And guess what? The pretty much cancel each other in the conductor leaving an almost zero net electric field inside. Perfectly compliant with Ohm's law. The same superposition leaves a perfectly Ohm compliant resultant E field in both resistors. But being the resistance different, the field inside will be different as well.
Now, let's do 2+2: on branch 1 we have 0 field in the upper arc of conductor, strong E1 field inside the R1 resistor, and 0 field in the lower arc of conductor. The voltage is the same as that along the resistor alone: Vad1 = E1*deltaL, where deltaL is the length of the resistor.
In branch 2, for the same reasons we have Vad2 = E2*deltaL. Since the net electric field is different in the two resistors, we get Vad1 != Vad2
Hopefully you do agree that battery is EMF source, right?
If solenoid does not influence voltmeter leads in Romer's/Lewin's circuit then it does not matter what kind of EMF source we are using, right?
So, I take 1.5V button-cell battery with internal 100 Ohm resistance and bigger 1.5V battery with 10 Ohms internal resistance, connect them "in series" (yes, small battery is reversed). You say that somehow we can measure different voltages between two points where batteries are connected together - we place voltmeter next to button cell battery, it shows one voltage then we move voltmeter to other side next to bigger battery and we have different reading? Wow :-DD Yes, this is what Romer and Lewin are trying to prove, just with other kind of EMF source rather than batteries.
If your theory is correct it must predict what happens when you change something in the experiment, and that prediction must perfectly match experimental results.
Hopefully you do agree that battery is EMF source, right?A localized EMF source, to be precise.
You can redo your experiment for localized EMF sources using two localized inductive EMF sources. One lumped secondary on the left, one lulmped secondary on the right and you will see that voltage won't be path dependent.
There is no problem to make two "distributed' batteries that resembles physical layout of Dr.Levin's test circuit. So what?
How about more than half-turn of Lewin's transformer? Let's say, one full turn for each "resistor"? According to your logic it automagically becomes localized EMF source and voltages are not path-dependent anymore?
Maybe for you. Hence the importance of a formal education,
Which you don't have.Quotewhere with the proper guidance not only the correct knowledge is acquired in a timely manner,
Yeah. Become an electronics engineer in just six months. Apply here!Quotebut the BS that characterizes team Lewin is weeded out.
If you really had a formal education in electronics engineering...QuoteVery well genius: explain what is it a non-conservative field, in the context of Lewin's ring!
...you wouldn't be asking me to explain to you what a non-conservative field is.
QuoteVery well genius: explain what is it a non-conservative field, in the context of Lewin's ring!
...you wouldn't be asking me to explain to you what a non-conservative field is.
Robert Romer's paper explains exactly what is non-conservative about the Lewin ring. I suggest jesuscf rereads it. I had to take a semester long course in vector calculus to understand this. Kudos to anyone who can truly understand the mathematics (and all the prerequisites) required for this in a couple of weeks! Even more so if they retain this knowledge. Some of the EE students I teach have already forgotten a lot of the vector calculus by the time they get to my lab courses on power machinery.
http://www.fisica.uns.edu.ar/albert/archivos/15/119/420063006_tp_y_guias.pdf (http://www.fisica.uns.edu.ar/albert/archivos/15/119/420063006_tp_y_guias.pdf)
That is where you are massively wrong. If your theory is correct it must predict what happens when you change something in the experiment, and that prediction must perfectly match experimental results. That is what KVL does every single time!!! So go ahead, make your prediction!
On that thought, why don't you retry your experiment with the resistor ring with a slight change, so that the magnetic flux geometry isn't in complete symmetry with your ring, but slightly off-center? Trevor Kearney suggested this as a challenge to those who support the idea of the scalar PD between two points being the "unique" voltage in the "Lewin Ring".
You will find that the "tiny voltage sources" in your circuit suddenly have a different value in every little piece of the wire and that for anything but the most trivial geometries you will need a numeric EM field solver and a model perfectly matching you circuit, to calculate that voltage. That in itself is not problematic, what is the much bigger problem is that you will not be able to quantify the uncertainty in your calculation, because you cannot know how close your numeric model is to reality.
The next problem will be to actually measure the "unique voltage" as a proof for your models accuracy, because now your measurement setup will have to use real-world wires and all the electric fields you measure will of course depend on the path of those wires relative to the magnetic flux. So what do you do now? You already don't know to what degree you can trust your calculation (or simulation) and then you don't know if any discrepancy between the voltage you measure and your calculation is due to "bad probing" or "bad modeling". For an engineer, that's not a good point to be.
And it doesn't end there. The next problem will be repeatability, as any small change in geometry will throw off your calculation and measurements again.
The beauty of the Maxwell-Faraday equation is that is requires no knowledge about the magnetic flux or path geometry. It just requires that the path be closed (that's what the "circle" in the Integral sign means) and then gives a perfect relation between the "voltage" you measure and the time-varying magnetic flux in the area enclosed by said path and the only uncertainty is how precisely you can measure the voltage. The only snail to swallow is accepting that voltages can be non-unique and will depend on the path you measure them on.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
If your theory is correct it must predict what happens when you change something in the experiment, and that prediction must perfectly match experimental results.
Again: this is not my theory.
I wish it was. But not even in a thousand years I would be able to come up with such elegant, coherent and comprehensive theory. I can barely see beyond the shoulders of those giants who crafted it.
Yes, I can find what happens when you put two capacitors in a loop around a magnetic core. But the idealization of perfect conductors in between them could lead to problems. I suppose I can add a small finite resistance in the wires, and I will have a look a this problem because I find it interesting.
I cannot but notice that you did not specify the sort of excitation: is it a pulse (I guess it will lead to a short-lived oscillation), or a sinusoidal signal (we will end up with a capacitive divider, if there are no surprises), or worse a linearly changing magnetic flux that would try to force a constant current in the capacitors (this I have to think about)?
My take is that you did the experiments with a sinusoidal excitation. Is that correct?
But why is it that it's always "team Lewin" that has to solve your problems, while you guys never answer questions?
There is no problem to make two "distributed' batteries that resembles physical layout of Dr.Levin's test circuit. So what?
The problem is that if you replace the battery with say 100 tiny batteries, you are still using lumped localized batteries. You will no longer have simple conducting wires connecting the resistors.
QuoteHow about more than half-turn of Lewin's transformer? Let's say, one full turn for each "resistor"? According to your logic it automagically becomes localized EMF source and voltages are not path-dependent anymore?
You need to see where the variable magnetic region is, with respect to the circuit path.
Inside.
Outside.
They are different concepts.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
That is where you are massively wrong. If your theory is correct it must predict what happens when you change something in the experiment, and that prediction must perfectly match experimental results. That is what KVL does every single time!!! So go ahead, make your prediction!
On that thought, why don't you retry your experiment with the resistor ring with a slight change, so that the magnetic flux geometry isn't in complete symmetry with your ring, but slightly off-center? Trevor Kearney suggested this as a challenge to those who support the idea of the scalar PD between two points being the "unique" voltage in the "Lewin Ring".
You will find that the "tiny voltage sources" in your circuit suddenly have a different value in every little piece of the wire and that for anything but the most trivial geometries you will need a numeric EM field solver and a model perfectly matching you circuit, to calculate that voltage. That in itself is not problematic, what is the much bigger problem is that you will not be able to quantify the uncertainty in your calculation, because you cannot know how close your numeric model is to reality.
The next problem will be to actually measure the "unique voltage" as a proof for your models accuracy, because now your measurement setup will have to use real-world wires and all the electric fields you measure will of course depend on the path of those wires relative to the magnetic flux. So what do you do now? You already don't know to what degree you can trust your calculation (or simulation) and then you don't know if any discrepancy between the voltage you measure and your calculation is due to "bad probing" or "bad modeling". For an engineer, that's not a good point to be.
And it doesn't end there. The next problem will be repeatability, as any small change in geometry will throw off your calculation and measurements again.
The beauty of the Maxwell-Faraday equation is that is requires no knowledge about the magnetic flux or path geometry. It just requires that the path be closed (that's what the "circle" in the Integral sign means) and then gives a perfect relation between the "voltage" you measure and the time-varying magnetic flux in the area enclosed by said path and the only uncertainty is how precisely you can measure the voltage. The only snail to swallow is accepting that voltages can be non-unique and will depend on the path you measure them on.
But will KVL hold after everything you listed above? Of course yes! Furthermore, the voltage potential difference between two arbitrary nodes will be a unique scalar at any fixed time t. Do you understand the difference of the voltage between two nodes and the voltage you measure between those two nodes? As soon as you measure the voltage in any circuit, the instrument is modifying the circuit, and if you don't account for that, the results you get may be so baffling as to make you proclaim that "KVL is for the birds".
My question would be: do you really believe that Dr. Lewin is such a massive fool that he didn't understand that the volt meters (or oscilloscopes) he used and the paths they were connected through were part of the circuit?
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
With regards to whether KVL holds in that circuit or not - it doesn't, in the circuit Lewin chose for his experiment. It may very well hold in the circuit you created, but it is a different circuit, by your own words, because the electric fields are observed along different paths. It is also very, very peculiar and so full of uncertainties that it will be very hard for you to claim that the results you obtained are "exact" and "true". Your measurements were one or two percent off from your calculation as I recall, but can you say where that error came from? Probing? Calculation? Assumptions? Resistor tolerance? Volt meter error? That's why I called it a Nothing-Burger.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
Ah, no. The right part doesn't "make" the left part conservative. The right part just says "there is a time-varying magnetic flux" and the left part says "there's an electric field with a curl", and the curl is what makes the left part non-conservative. As to answer the "where", the "curled" electric field is in a plain perpendicular to the magnetic flux vector.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
Ah, no. The right part doesn't "make" the left part conservative. The right part just says "there is a time-varying magnetic flux" and the left part says "there's an electric field with a curl", and the curl is what makes the left part non-conservative. As to answer the "where", the "curled" electric field is in a plain perpendicular to the magnetic flux vector.
Yes it does! That is why KVL do work.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
Ah, no. The right part doesn't "make" the left part conservative. The right part just says "there is a time-varying magnetic flux" and the left part says "there's an electric field with a curl", and the curl is what makes the left part non-conservative. As to answer the "where", the "curled" electric field is in a plain perpendicular to the magnetic flux vector.
Yes it does! That is why KVL do work.
Emphasis mine. Is there a typo here? Are you saying that the curl of E being 0 means the field is non-conservative?
Have you taken a course in vector calculus or are you self-taught on this subject?
With regards to whether KVL holds in that circuit or not - it doesn't, in the circuit Lewin chose for his experiment. It may very well hold in the circuit you created, but it is a different circuit, by your own words, because the electric fields are observed along different paths. It is also very, very peculiar and so full of uncertainties that it will be very hard for you to claim that the results you obtained are "exact" and "true". Your measurements were one or two percent off from your calculation as I recall, but can you say where that error came from? Probing? Calculation? Assumptions? Resistor tolerance? Volt meter error? That's why I called it a Nothing-Burger.
The main source of error, I believe, is probing. One has to be very careful for the varying magnetic field not to affect the measuring instruments. I find it interesting that you are willing to dismiss my experiment because I got a less than 2% discrepancy with the theoretical KVL calculation, but you are willing to immediately accept Lewin's results when he doesn't even provide any actual numerical measurements from his experiment.
Also, have you done the experiment yourself? Do you have any measurements?
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
Ah, no. The right part doesn't "make" the left part conservative. The right part just says "there is a time-varying magnetic flux" and the left part says "there's an electric field with a curl", and the curl is what makes the left part non-conservative. As to answer the "where", the "curled" electric field is in a plain perpendicular to the magnetic flux vector.
Yes it does! That is why KVL do work.
Emphasis mine. Is there a typo here? Are you saying that the curl of E being 0 means the field is non-conservative?
Have you taken a course in vector calculus or are you self-taught on this subject?
Yes, the old good "Straw Man Fallacy". Here, read it from Hayt yourself, from the attached pdf.
Ok, then in three small sentences or less explain where the non-conservative field is in Lewin's ring.
\${\nabla \times E = -\frac{\partial B}{\partial t}}\$
Hint: left side of the equation.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
\${\nabla \times E = 0}\$
Ah, no. The right part doesn't "make" the left part conservative. The right part just says "there is a time-varying magnetic flux" and the left part says "there's an electric field with a curl", and the curl is what makes the left part non-conservative. As to answer the "where", the "curled" electric field is in a plain perpendicular to the magnetic flux vector.
Yes it does! That is why KVL do work.
Emphasis mine. Is there a typo here? Are you saying that the curl of E being 0 means the field is non-conservative?
Have you taken a course in vector calculus or are you self-taught on this subject?
Yes, the old good "Straw Man Fallacy". Here, read it from Hayt yourself, from the attached pdf.
Have you read it? No strawman here. I seriously have no idea WTF you're talking about because on the very page you cited, Hayt writes:
"Any field that satisfies an equation of the form of Eq. (20), (i.e., where the closed
line integral of the field is zero) is said to be a conservative field."
You wrote,
"The only way it will be non-conservative is if you do this:
∇×E=0"
Which is the opposite of what Hayt wrote. Is this a typo? Or have you self-taught yourself vector calculus? Those are the only two possibilities I can think of for such a statement.
Hayt goes on to write,
"The integral is zero if ρ1 = 1, 2, 3,... , etc., but it is not zero for other values of ρ1,
or for most other closed paths, and the given field is not conservative. A conservative
field must yield a zero value for the line integral around every possible closed path."
There are paths in the Romer-Lewin ring whose line integrals are non-zero. Proof by counterexample then is that the field is non-conservative, KVL doesn't hold (as it requires 0 line integral around every path, as Feynman writes), and voltage is non-unique in the presence of non-conservative fields.
How is this even a debate?
I should mention that, strictly speaking, a vector field with zero curl CAN be non-conservative. That is, zero curl does not imply the field is conservative.
https://mathinsight.org/path_dependent_zero_curl
This is why I, personally, much prefer the integral representation of Maxwell's Eqs than the differential form.
I wish I had this website when I went to college. Their examples and details are quite nice:
https://mathinsight.org/conservative_vector_field_determine
With regards to whether KVL holds in that circuit or not - it doesn't, in the circuit Lewin chose for his experiment. It may very well hold in the circuit you created, but it is a different circuit, by your own words, because the electric fields are observed along different paths. It is also very, very peculiar and so full of uncertainties that it will be very hard for you to claim that the results you obtained are "exact" and "true". Your measurements were one or two percent off from your calculation as I recall, but can you say where that error came from? Probing? Calculation? Assumptions? Resistor tolerance? Volt meter error? That's why I called it a Nothing-Burger.
The main source of error, I believe, is probing. One has to be very careful for the varying magnetic field not to affect the measuring instruments. I find it interesting that you are willing to dismiss my experiment because I got a less than 2% discrepancy with the theoretical KVL calculation, but you are willing to immediately accept Lewin's results when he doesn't even provide any actual numerical measurements from his experiment.
Also, have you done the experiment yourself? Do you have any measurements?
I don't dismiss your experiment because of those 2%, but because you cannot say where they come from. You "believe" the error is from probing. That means you're absolutely sure that your calculation (and thus assumptions) are correct. Why? Your approach to modeling was trivially assuming complete uniformity in distribution of the scalar PD. How can you be sure of that?
I can surely repeat the experiment as soon as I've found my stash of ring cores that is hidden somewhere in the pile of boxes from the last move. But I'm reasonably sure that I'll just observe what others have already found.
Hayt goes on to write,
"The integral is zero if ρ1 = 1, 2, 3,... , etc., but it is not zero for other values of ρ1,
or for most other closed paths, and the given field is not conservative. A conservative
field must yield a zero value for the line integral around every possible closed path."
There are paths in the Romer-Lewin ring whose line integrals are non-zero. Proof by counterexample then is that the field is non-conservative, KVL doesn't hold (as it requires 0 line integral around every path, as Feynman writes), and voltage is non-unique in the presence of non-conservative fields.
How is this even a debate?
The only path allowed is the path of the circuit composed of wires and resistors. The integral does not apply to any other arbitrary path.
What I mean is that, over the influence of an external magnetic field, if you add the voltage drops from the resistors you'll get a number that is not zero. That is where the induced emf comes into play. The sum of the voltage drops in the resistors is equal to the induced emf. Energy in is equal to energy out. The circuit is conservative and KVL works. Is that clear now?
The only path allowed is the path of the circuit composed of wires and resistors. The integral does not apply to any other arbitrary path.
For Dr. Lewins experiment, it obviously needs to be pointed out that also the paths involving the measurement equipment are important. People seem to forget that, but it is key to understanding it. And of course the equation applies to every possible path through the circuit. How could it be any different.
What I mean is that, over the influence of an external magnetic field, if you add the voltage drops from the resistors you'll get a number that is not zero. That is where the induced emf comes into play. The sum of the voltage drops in the resistors is equal to the induced emf. Energy in is equal to energy out. The circuit is conservative and KVL works. Is that clear now?
This is not what conservative fields mean. Path-dependence is the key. I linked this to you pages and pages ago.
https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/8-2-conservative-and-non-conservative-forces/
Don't know how much simpler it can get.
And also why I asked if you were self-taught on this subject - you are confusing terminology and making an inconsistent theory.
What I mean is that, over the influence of an external magnetic field, if you add the voltage drops from the resistors you'll get a number that is not zero. That is where the induced emf comes into play. The sum of the voltage drops in the resistors is equal to the induced emf. Energy in is equal to energy out. The circuit is conservative and KVL works. Is that clear now?
This is not what conservative fields mean. Path-dependence is the key. I linked this to you pages and pages ago.
https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/8-2-conservative-and-non-conservative-forces/
Don't know how much simpler it can get.
And also why I asked if you were self-taught on this subject - you are confusing terminology and making an inconsistent theory.
In Lewin's ring can you please calculate the power added to the circuit by the external varying magnetic field (via Faraday's law) and compare it to the power consumed by the resistors? Is energy conserved in the circuit or not?
Your question is nonsensical in the context of this discussion. I also sent you this link.
https://courses.lumenlearning.com/physics/chapter/7-5-nonconservative-forces/
If you'd read this, or had any formal training in mathematics or physics (I'm happy to admit I received formal education, have you? I really am interested to know if you've ever passed exams on these topics), you'd see how ridiculous this question is when we are talking about non-conservative forces and fields. From the link above:
Are you asking if the energy consumed in the resistors to the Romer system is the same as the energy supplied by the field? Yes... obviously.
I don't know how much more explicitly you want it. In Romer's ring, since the voltage is the contribution of both the electric potential and the magnetic potential (whose contribution is a current flow from induction), and the magnetic potential is multi-valued depending on the path of integration, then there is no unique, single-valued voltage in the network.
It makes perfect sense, because the derivation of Kirchhoff's circuital laws are based in the principle of conservation of energy. And yes, I read the link you posted, and it completely agrees with what I am saying.
(Yes, I have received formal education: 5 years undergrad, 2 years masters, and 4 years PhD. What about you?)
Therefore the fields in the circuit are conservative, aren't they?
You are mixing magnetic circuits with electric circuits here. In the wire ring with two resistors we don't have a magnetic circuit. But since you are at it, please add a thermal circuit, and why not, a hydraulic circuit as well! All of those can be solved with laws equivalent to Ohms law, KVL, and KCL.
We should remember that the electrostatic potential V is a conservative field; the magnetic scalar potential Vm is not a conservative field.
If B is not a function of time, (5) and (6) evidently reduce to the electrostatic equations
It makes perfect sense, because the derivation of Kirchhoff's circuital laws are based in the principle of conservation of energy. And yes, I read the link you posted, and it completely agrees with what I am saying.
The KVL law predicts that voltage in a closed path must be zero regardless of path. That's not true in the presence of non-conservative fields, period.Quote(Yes, I have received formal education: 5 years undergrad, 2 years masters, and 4 years PhD. What about you?)
MSEE and 2 years Ph.D in progress and P.E. license.QuoteTherefore the fields in the circuit are conservative, aren't they?
Go directly to jail. Do not pass GO. Do not collect $200.
How can you read Hayt, have a formal education (I assume in EE), and come away with that conclusion about magnetic fields? It's astounding to me.
Here, try this maybe?
https://phys.libretexts.org/Bookshelves/Electricity_and_Magnetism/Book%3A_Electricity_and_Magnetism_(Tatum)/09%3A_Magnetic_Potential/9.01%3A_Introduction_to_Magnetic_PotentialQuoteYou are mixing magnetic circuits with electric circuits here. In the wire ring with two resistors we don't have a magnetic circuit. But since you are at it, please add a thermal circuit, and why not, a hydraulic circuit as well! All of those can be solved with laws equivalent to Ohms law, KVL, and KCL.
So the contribution of the magnetic field does not matter to you? No wonder you can't see the non-conservative interactions at play.
Hayt is using magnetic circuits as part of his progression in getting to the complete form of Faraday's Law. Chapter 4 is about electrostatic fields, where all the fields are conservative, work done on any path is zero, and KVL can happily be applied.
But trouble starts to happen when the magnetic fields come in and start to wobble a little. Hayt writes on P.212,QuoteWe should remember that the electrostatic potential V is a conservative field; the magnetic scalar potential Vm is not a conservative field.
That is achieved by simply taking the closed loop line integrals of H (H and B are related directly by permeability constant so its trivial to do the unit conversions) and seeing that they no longer have unique values.
So what happens when we take the derivative of those B-fields and those derivative are not zero and then we integrate them?
By Chapter 9, KVL is gone. Hayt writes (P.280),QuoteIf B is not a function of time, (5) and (6) evidently reduce to the electrostatic equations
Which are just the KVL equations of Chapter 4. If B IS a function of time, then those equations can't reduce - KVL doesn't exist here, the closed loop contours are now entirely path dependent.
See, the trick is in seeing that magnetic forces on a charge in a magnetic field are not, by their nature, conservative. But, if they don't vary with time - everything is cool. Their derivative is zero and they disappear. Yet, if they DO vary with time - then all the nasty complications of path-dependency analyzed in Chapter 7 MUST be taken into account. Chapter 9 does this - but KVL cannot live in Chapter 9 because KVL is said, repeatedly by Hayt, to be path independent.
Faraday's Law is not. And can never be. Voltages in the presence of time-varying fields are not unique.
You are very confused by what you are reading. For instance, can you provide a guesstimate of the reluctance of the ring circuit? Assume the wiring is either copper or aluminum. How would that affect the electric behavior of the ring circuit?
In an electric circuit, the voltage source is a part of the closed path; in the magnetic circuit, the current-carrying coil will surround or link the magnetic circuit. In tracing a magnetic circuit, we will not be able to identify a pair of terminals at which the magnetomotive force is applied. The analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero).
In other words, Kirchhoff’s voltage law states that the rise in potential through the source is exactly equal to the fall in potential through the load.
The analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero)
You are very confused by what you are reading. For instance, can you provide a guesstimate of the reluctance of the ring circuit? Assume the wiring is either copper or aluminum. How would that affect the electric behavior of the ring circuit?
And phhhewwwwww away we go. It's funny you should ask this though as if it's some kind of gotcha question. Hayt has a discussion of this too:QuoteIn an electric circuit, the voltage source is a part of the closed path; in the magnetic circuit, the current-carrying coil will surround or link the magnetic circuit. In tracing a magnetic circuit, we will not be able to identify a pair of terminals at which the magnetomotive force is applied. The analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero).
So, the MMF of equation 44 on P.257 is entirely dependent on the number of loops of the coil enclosing the circuit. In other words, the value of the MMF changes based on how many times you circumscribe the closed loop path.
Hayt defines on P.256 that the Reluctance of a circuit is a function of the magnetic scalar potential (which we saw from Chapter 7.6 is path dependent). The units are A-t/Wb. So, the Reluctance is also path-dependent.
And I like how Hayt tosses in, for good measure, a reminder that closed line integral of E is NOT zero in this circuit or the circuits of Chapter 9 which is also explicitly the definition of a non-conservative field. I think he mentions this because on P.256 he writes after showing the closed loop integral of E dot dl,QuoteIn other words, Kirchhoff’s voltage law states that the rise in potential through the source is exactly equal to the fall in potential through the load.
Once more for the people in the back? What does he write on the very next page of P.257?QuoteThe analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero)
Can we stop with this fiction that Hayt somehow agrees with the cockamamie proposition that KVL holds in all cases? He doesn't. None of the published authors do - because it's wrong.
Once again, we are not dealing with a magnetic circuit here.
The analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero)
Once again, we are not dealing with a magnetic circuit here.
That is why you fail. I've taken you, step-by-step, through Hayt's progression from electrostatics, into magnetic circuits (where the non-conservative properties of magnetism are explored), and how they directly lead to the conclusions of Chapter 9, which Hayt teased in Chapter 8, and I quote again,QuoteThe analogy is closer here to a pair of coupled circuits in which induced voltages exist (and in which we will see in Chapter 9 that the closed line integral of E is also not zero)
Your answer is the equivalent of saying,
"Nuh uh!"
A Ph.D. is telling me that the properties of magnetic fields do not apply to the Romer ring. I guess Hayt was just navel-gazing in Chapters 7 and 8 and none of that stuff has anything to do with Chapter 9...
I'm truly astounded (and I guess I now understand Lewin's comments in his lecture about being accused of cheating on the experiment). Unless you have something substantive, I am not replying to your comments anymore.
Great, from now on I will try not reply to your messages either as I am tired of your fallacious diatribe.
Yes, but the right part of the equation makes it conservative again! The only way it will be non-conservative is if you do this:
∇×E=0
Therefore the fields in the circuit are conservative, aren't they?
Not pointing it out and hoping people missed it--perhaps expecting the curled e-field resulting from the changing magnetic flux to somehow stop at the perimeter of the inner ring--was the sole basis for this being a memorable, 'miind-blowing' demonstration.
The funny thing about this whole "energy conservative" stuff is, there has to be a source of energy in the first place, for the circuit to consume it. This source of energy can be either lumped or not. If the physical circuit allows for it, you can lump the energy source into a two-terminal component and put it actually into the circuit. In other circuits, like in Dr. Lewins experiment, you can not do it. You're forced to admit that the energy source is external to the circuit and has no discrete source, and this is where KVL stops working.
The reason is simply because such circuit is not energy conservative. The energy source is not IN the circuit. This breaks the very foundation on which KVL is based.
The funny thing about this whole "energy conservative" stuff is, there has to be a source of energy in the first place, for the circuit to consume it. This source of energy can be either lumped or not. If the physical circuit allows for it, you can lump the energy source into a two-terminal component and put it actually into the circuit. In other circuits, like in Dr. Lewins experiment, you can not do it. You're forced to admit that the energy source is external to the circuit and has no discrete source, and this is where KVL stops working.
The reason is simply because such circuit is not energy conservative. The energy source is not IN the circuit. This breaks the very foundation on which KVL is based.
I see you are a lot more confused that I thought you were. Let me try to explain, in the simplest possible terms what is going on:
This is how Lewin calculated (correctly by the way) the loop current through the circuit:
\$I=\frac{emf}{R_{1}+R_{2}}\$
Or, rearranging a bit, so that you can clearly see what is going on:
\$I^{2}R_{1}+I^{2}R_{2}=emf\cdot I\$
Can you read what the equation above is telling you? If you are not happy with the units of the equation, multiply both sides by some arbitrary time to find the energy added or consumed by the circuit during that time.
And it is conservative because the magnetic field outside the solenoid is precisely dick.
The funny thing about this whole "energy conservative" stuff is, there has to be a source of energy in the first place, for the circuit to consume it. This source of energy can be either lumped or not. If the physical circuit allows for it, you can lump the energy source into a two-terminal component and put it actually into the circuit. In other circuits, like in Dr. Lewins experiment, you can not do it. You're forced to admit that the energy source is external to the circuit and has no discrete source, and this is where KVL stops working.
The reason is simply because such circuit is not energy conservative. The energy source is not IN the circuit. This breaks the very foundation on which KVL is based.
I see you are a lot more confused that I thought you were. Let me try to explain, in the simplest possible terms what is going on:
This is how Lewin calculated (correctly by the way) the loop current through the circuit:
\$I=\frac{emf}{R_{1}+R_{2}}\$
Or, rearranging a bit, so that you can clearly see what is going on:
\$I^{2}R_{1}+I^{2}R_{2}=emf\cdot I\$
Can you read what the equation above is telling you? If you are not happy with the units of the equation, multiply both sides by some arbitrary time to find the energy added or consumed by the circuit during that time.
Just tell me where in the circuit of Dr. Lewin you find "emf" and we're good. Note: you're not allowed to change the measurement results.
And it is conservative because the magnetic field outside the solenoid is precisely dick.
Solenoid EM fields are miraculously nonexistant for voltmeter leads running next to the test circuit parts. Right. :-DD
Watch Lewin's lecture 15 where he probes a solenoid with a calibrated Hall sensor.
So, in Lewin's setup, where he puts the ring midway from the ends of the solenoid, there's no varying magnetic field outside. Therefore there will be no non-conservative electric field that could interfere with the probes connected to the circuit.
Watch Lewin's lecture 15 where he probes a solenoid with a calibrated Hall sensor.
So, in Lewin's setup, where he puts the ring midway from the ends of the solenoid, there's no varying magnetic field outside. Therefore there will be no non-conservative electric field that could interfere with the probes connected to the circuit.
Seems, you did not get what I was saying. Rephrased sentence: Solenoid EM fields that causes EMF in the test circuit, are miraculously nonexistant for voltmeter leads running next to the test circuit parts.
[edit] Those who are impatient waiting for answer from "Dr.Lewin's science guru", can try to find answer empirically. All what's needed - AC mains transformer, insulated wire and AC voltmeter. Try to measure EMF for 1) single turn - tightly wrapped around core, then 2) big enough loop that would imitate voltmeter leads not receiving any EMF. 3) compare. Sample configuration for supposedly most popular E-E core transformer attached. Note that test wire is going through outer leg of "E". Comments about your test results are welcome. Do not hesitate to make even bigger loops than shown in M2 pic.
I just got my Fluke 187 working again, so with the help of an small audio transformer, a function generator (sine wave, 1 kHz, 20Vpp), and my Brymen BM869s, I got what is shown in the attached picture.
Why should the size/diameter/area of the loop make any difference, as long as it loops through the core?
Why should the size/diameter/area of the loop make any difference, as long as it loops through the core?
Bingo. Size/diameter/area does not matter in Maxwell-Faraday equation. It also means that two circuits show in attachment are equivalent and will show equal readings on voltmeter. Those who are familiar with Romer's/Lewin's experiment and still believe that it is not "probing error", can take a moment to sink it in. Yes, it comes from Romer's paper, edited using windows paint (lol).
[edit] All this just to frustrate students and fellow scientists with resistive divider which *itself* receives EMF from EM induction. Obviously KVL holds. EMF = I*(R1 + R2), V1 = EMF * R1/(R1+R2), V2 = EMF * R2/(R1+R2)
Bingo. Size/diameter/area does not matter in Maxwell-Faraday equation. It also means that two circuits show in attachment are equivalent and will show equal readings on voltmeter. Those who are familiar with Romer's/Lewin's experiment and still believe that it is not "probing error", can take a moment to sink it in. Yes, it comes from Romer's paper, edited using windows paint (lol).
[edit] All this just to frustrate students and fellow scientists with resistive divider which *itself* receives EMF from EM induction. Obviously KVL holds. EMF = I*(R1 + R2), V1 = EMF * R1/(R1+R2), V2 = EMF * R2/(R1+R2)
Err, yes.. But that was entirely not the point of Lewin's experiment.
Bingo. Size/diameter/area does not matter in Maxwell-Faraday equation. It also means that two circuits show in attachment are equivalent and will show equal readings on voltmeter. Those who are familiar with Romer's/Lewin's experiment and still believe that it is not "probing error", can take a moment to sink it in. Yes, it comes from Romer's paper, edited using windows paint (lol).
[edit] All this just to frustrate students and fellow scientists with resistive divider which *itself* receives EMF from EM induction. Obviously KVL holds. EMF = I*(R1 + R2), V1 = EMF * R1/(R1+R2), V2 = EMF * R2/(R1+R2)
Err, yes.. But that was entirely not the point of Lewin's experiment.
AFAIK point of Lewin's experiment was to prove that voltages in his test circuit are "path-dependent" and "KVL is for birds". Both statements are simply BS. Old man frustrated himself with overcomplicated experiment. [edit] You can't agree to both - my equations *and* Lewin's equations (attached)
Bingo. Size/diameter/area does not matter in Maxwell-Faraday equation. It also means that two circuits show in attachment are equivalent and will show equal readings on voltmeter. Those who are familiar with Romer's/Lewin's experiment and still believe that it is not "probing error", can take a moment to sink it in. Yes, it comes from Romer's paper, edited using windows paint (lol).
[edit] All this just to frustrate students and fellow scientists with resistive divider which *itself* receives EMF from EM induction. Obviously KVL holds. EMF = I*(R1 + R2), V1 = EMF * R1/(R1+R2), V2 = EMF * R2/(R1+R2)
Err, yes.. But that was entirely not the point of Lewin's experiment.
AFAIK point of Lewin's experiment was to prove that voltages in his test circuit are "path-dependent" and "KVL is for birds". Both statements are simply BS. Old man frustrated himself with overcomplicated experiment. [edit] You can't agree to both - my equations *and* Lewin's equations (attached)
Voltages ARE path-dependent. What you fail to see is that in order to see the path dependency you have to enclose a variable flux region between the paths. In the case of Lewin's ring
Voltages ARE path-dependent. What you fail to see is that in order to see the path dependency you have to enclose a variable flux region between the paths. In the case of Lewin's ring
Yes, the voltage generated in the voltmeter test leads depends on the path--i.e. where you put them. >:D
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1367822;image)
Those who are familiar with Romer's/Lewin's experiment and still believe that it is not "probing error", can take a moment to sink it in.
Here, I fixed Lewin's blackboard to match reality.
EDIT: Awwww! Now I get it. :palm:
I need time not to see the probing error, but to absorb the impact of the stupidity of KVLers.
Voltages ARE path-dependent. What you fail to see is that in order to see the path dependency you have to enclose a variable flux region between the paths. In the case of Lewin's ringYes, the voltage generated in the voltmeter test leads depends on the path--i.e. where you put them. >:D
Well, I would have drawn that purple, to match the picture below but... what do you think you have accomplished pointing that out?
The circuit below already showed path dependent voltages. That you have drawn is a 0V path - it is measuring the voltage along the transformer coil.
Voltages ARE path-dependent. What you fail to see is that in order to see the path dependency you have to enclose a variable flux region between the paths. In the case of Lewin's ringYes, the voltage generated in the voltmeter test leads depends on the path--i.e. where you put them. >:D
Well, I would have drawn that purple, to match the picture below but... what do you think you have accomplished pointing that out?
The circuit below already showed path dependent voltages. That you have drawn is a 0V path - it is measuring the voltage along the transformer coil.
So you are saying - to measure voltage for given path, one shall route voltmeter leads along that path? In case I have only one voltmeter, I need to place voltmeter and it's leads on right side of Lewin's experiment to measure voltage on right side resistor, as soon as I move voltmeter and leads to left side - I suddenly measure voltage on left side resistor? This is not because of electromagnetic induction but "path dependency"?
I wonder - how one can practically demonstrate path-dependency using transformer with let's say, 100 turns of secondary? He shall wind 100 turns of voltmeter leads on transformer core or what? Would be good to get description of experiment so those who are interested, can repeat. Thank you.
You make a very good point here. Sredni's "path dependency" is less and less noticeable the more turns on the secondary. I did the experiment with a three turn secondary and posted the results in this forum. Sredni almost calculated the voltage between nodes A and D, VAD but suddenly realized that if he did the calculation he would show that KVL works perfectly, and backed up quickly...
Cyriel Mabilde in Youtube did a similar experiment too with a five turn secondary and also demonstrated that KVL works perfectly. Now I am waiting for some insight from Sredni of what would happen if we replace the resistors in the loop with capacitors, but he is MIA...
So you are saying - to measure voltage for given path, one shall route voltmeter leads along that path?
When I measure from the outside of the ring, since the dB/dt is well inside the ring, there is no dB/dt region inside my measurement loop, so if we look at it in 2D in the area enclosed by the loop voltage is not path-dependent and the value along the branch I test is ALSO the value across the branch I test which is ALSO the value across the probes and voltmeter, which is ALSO the value shown by the voltmeter.
When I measure from the outside of the ring, since the dB/dt is well inside the ring, there is no dB/dt region inside my measurement loop, so if we look at it in 2D in the area enclosed by the loop voltage is not path-dependent and the value along the branch I test is ALSO the value across the branch I test which is ALSO the value across the probes and voltmeter, which is ALSO the value shown by the voltmeter.
I wonder - how dB/dt discerns between wires of resistor and voltmeter leads? You think that EMF miraculously stops at first wire it encounters, acts only on circuit but not on voltmeter leads? Then please explain how multi-turn transformers work?
Also you did not answer my 2nd question: how one can practically demonstrate path-dependency using transformer with let's say, 100 turns of secondary.
You clearly have a very fuzzy recollection of those events.
I computed all the values in your silly circuits in less than 15 minutes and got the results right. Including the voltage along a diameter in the case of perfectly circular and concentric geometry.
You still cannot understand that voltage IS path dependent.
Mabilde, from the depth of his garage, is another KVLer who cannot imagine a path dependent quantity. And this is an old movie that is being rerun over and over. The KVLers propose their 'killing' experiments that should make us "Armchair Nobel prize physicists" fly away to another galaxy. Then we post the solutions according to classical ED (it's not 'our' theory, it's plain old classical electrodynamics) and you fade to silence for a while, except coming back with muddy recollections of events.
It happened with the 'two secondaries is series', it happened with the straight partial coil, it happened with the multiturn coil, it happened with that sentence by Belcher (Jesse is still touting it in his boilerplate answer on his channel and he is forced to ban users who do not agree with him to make them 'fly away to another galaxy')...
...and now we are at the ring with two capacitors. As if these capacitors could change something.
So, here, are the results for the following values of capacitors
C1 = 4.7 uF , C2 = 22 uF
freq = 50 Hz
emf = 374 mV
I get - from simulation and without even invoking MEAS, just by eyeballing the plots
VcapL = 308.5 mV, VcapH = 65.5 mV
Guess what I measure with a true RMS multimeter?
VcapL = 308 mV, VcapH = 66 mV
And nothing, ok almost nothing, in the copper joining the caps.
So, what are the revolutionary results that you said were bad news for 'team Lewin'?
I don't think I have to repeat what I already wrote in the last thirty or so pages. Re-read them if you want.
You touted this 'two capacitor' example as the (yet another) definitive circuit that would jave brought 'team Lewin' to the ground.
It turned out not to be at all different from the original ring with two resistors.
In steady state resistances are exchanged with reactances. The induced field drives charges on the plates of the capacitors and instead of a conduction current we end up with a displacement current.
The setup is the same as that I used for the ring with the two resistors: a ring with two resistors around a toroidal core. There are no surprises. Everything is as it should be: a drop of 308 mV on the 4.7uF cap, negligible - basically zero - drops in the copper section, and a drop of 66 mV in the 22 uF cap.
This time I didn't attach the scope's probes, but I would have seen the same 180 degrees phase inversion.
If you want to waste time, you can compute the reactances, and the current.
I am asking you again: why did you insist this example was something special? It was a dud.
I am asking you again: why did you insist this example was something special? It was a dud.
Will a ring made exclusively out of capacitors show an induced emf? No wires, only capacitors in series replacing the ring, as well as the two original resistors on each side. What would be the voltage VAD in this case? Do you agree that now that there are not 'Lewin zero volt' short circuits anywhere?
I am asking you again: why did you insist this example was something special? It was a dud.
Will a ring made exclusively out of capacitors show an induced emf? No wires, only capacitors in series replacing the ring, as well as the two original resistors on each side. What would be the voltage VAD in this case? Do you agree that now that there are not 'Lewin zero volt' short circuits anywhere?
And here we go again.
After the nth "killer question" is answered, not a comment.
And then "killer question" n+1 takes its place.
Answer that and the cycle repeats.
What if we made a ring of alternating capacitors and thermistors?
And a ring with thermocouples orbiting a neutron star?
What about a ring made of anti-matter?
And what if we changed the gravitational constant of the universe?
You are just wasting people's time.
When Lewin argues that the voltage between the terminals of the opposing resistors in the ring is zero or that the induced voltage in the voltmeter probes is also zero, he is incorrect, and that is the source of this controversy. The guy messed up and he won't admit it. He even went so far as of trying to change the definition of KVL. Too bad for Lewin that Maxwell himself wrote the definition of KVL in his 1873 book, which contradicts what he says.
Let the components of the current at any point be u, v, w.
[...]
By Ohm's Law the current is proportional to the electromotive intensity. Hence X, Y and Z must be linear functions of u, v, w. We may therefore assume as the equations of Resistance,
X = R1u + Q3v + P2w,
Y = P3u + R2v + Q1w,
Z = Q2u + P1v + R3w.
So, the resultant EMF inside a wire no matter its multiple origins must be its current multiplied by its resistance. So much for modelling a wire as a resistance in series with a battery. This agrees perfectly with what is being said all the time: the wires and resistors in Lewin's circuit only have a voltage that is their respective resistance times the current intensity and nothing else.
Also you did not answer my 2nd question: how one can practically demonstrate path-dependency using transformer with let's say, 100 turns of secondary.When you measure from the outside you can look at the measure in two ways:
the voltmeter shows the actual voltage in the gap between taps
the voltmeter shows the voltage along the portion of filament between the taps (which is the ohmic drop that is nearly zero volts) plus (or minus depedending on orientation) the linked emf (emf of one turn times integer number of turns linked).
This has been one heck of a ride.
Really the first thing I need to get off my chest is, I really appreciate the work by bsfeechannel and Sredni, and later thinkfat. Thank you for not giving up, and I also need to apologize. I don't remember what I exactly posted on the previous round (is it already two years or what?) but it was about bsfeechannel's writing style and completely uncalled for. Seeing how much pure stupidity you have to deal with, I admire the coolheadness you can still maintain.
Thank you for revisiting this again, because the fact that time has passed helps to see it in new light. It's also amusing to see how many have "converted". For the rest, quality is indeed going down.
Additionally to thinkfat doing full 180, my real eye openers were actually helpful comments by jesuscf and Jesse.
These guys repeatedly called all the math used gibberish, confusing, etc. etc., and it really hit home because I agree with them. Math as shown by Sredni is pretty much gibberish to me, as well. But there is one big difference; while hate admitting being wrong as well, I hate intellectual dishonesty even more. I simply can't go there.
Which gets us into the matter of credentials as discussed repeatedly. Personally, still in high school I really shone in math. Those integrals were a breeze. Coming to university however, the first few courses were still with full scores, but then my scores started dropping. It seems, while integrals as taught in high school were easy, now when multiple integral symbols with those small extra symbols like circles started to appear, number of different alphabets and writing styles to signify different entities blew through the roof, it become harder. I was able to pass exams still but had fundamental issues digesting it.
It didn't help that my curriculum was kind of special mix, originally designed to mass-produce design engineers for still growing Nokia (which later colossally failed), but I'm not sure if that mix worked that well. Only one course in very fundamental electromagnetism (dealing with these subjects) so while we had all the related math, it was disconnected. I never learned the Maxwell equations well. Then we mostly had signal processing, some computer science, some electronics, etc.
Finally, I failed the exam in vector analysis. This was the first time me literally failing math. In the end, I admitted the fact that I'm just not a math wizard, and I don't need to be. Different people have different skills. I know enough math to know what I need to know, so that I can ask for help from the right people if the task requires it. This also makes me appreciate those who can deal with complex math. Their skills and understanding in electromagnetics have enabled all the nice modern things we have, so that more simple-minded engineers like myself can just buy a lumped module which deals with all the voodoo internally.
And now we get back to the eye opening moments. The bullshit generated by J & J in this thread could work for some readers, say, a carpenter or plumber with no university math background.
But for me, it doesn't work. Sredni's math might look gibberish-y enough for me so that I understand how J & J feel about it, but on the other hand, I still remember enough of the Vector Analysis and Electromagnetic fields and waves that I can see chances are very high Sredni knows exactly what he's talking about. Even if that is unsure, it's certainly sure that J & J have absolutely no idea about the math involved whatsoever, even if they are capable of copy-pasting some terms and putting them together to form sentences cargo cult way - think about "lumpable paths" & co.
So, finaly I asked myself what is the real dispute here, behind the endless loop of fog screens.
It is the question:
Is Lewin's original circuit lumpable?
Because non-lumpability is hard to prove (like nonexistence of God), requiring mathmematical concepts not everybody seemingly understand or agree about, the burden of proof has to be turned around: prove that KVL works.
And I think the only sustainable, intellectual honest way of debating about this would be this very process:
* Show an equivalent circuit -> show that the real circuit behaves like that equivalent circuit
* Now disputing this is easy; just show how the given equivalent circuit does not work. Single datapoint suffices.
* Now the author is required to come up with a new equivalent circuit, until it works - or doesn't.
And this is what I have not seen. I'm serious. I have not seen a circuit diagram, showing an equivalent circuit, and Kirchoff based calculations that get the result matching with the experiment.
Instead, I have seen videos of special 3D arrangements made for the task.
So I think I know where the issue lies.
It's the fact that a 2D circuit drawing with nodes, KVL applied, is not sufficient alone. To get it working, extra "hidden" information is added; not necessarily even hidden, not everyone is dishonest with this, but nevertheless it seems the exact 3D construction is the crucial part. This cannot be conveyed with simple circuit mesh diagram, otherwise it would have been done already.
So the model is not a equivalent circuit that can be drawn as a diagram; no, the model is a photograph or usually even a video showing a careful 3D construction. Only within this model, the KVL seems to hold.
As soon as you change this model - while the 2D circuit diagram keeps the same! - the model breaks up. This is then called "bad probing".
But Kirchoff laws and simple 2D circuit diagrams with lumped components were never supposed to cover such complex cases. Sure, you can force this approach, by adding new layers of information (like, add a photograph describing the exact layout required, to the point of showing correct ways of probing), but then the question is, is this way of modeling beneficial? Or maybe going to the lower physical level with wider generalizations, using known, true and tested principles - for example, Maxwell equations on paper, or modern EM field solvers/simulators - would make more sense?
In any case, it's quite a mystery how this discussion actually started, and though I originally contributed this to Lewin's "flashy" way, I now think it's more because of how Mehdi represented it. After all, many have seen the Lewin's lecture, and it did mean nothing until Mehdi "set up the stage" so to speak, introducing the concept of "being wrong", which is actually quite ridiculous if you think about it deeper.
Lewin's lecture isn't that special; it's completely normal to see lecturers show examples "how not to do something". It's quite a stretch to think this shows that "the lecturer doesn't know how to do it". No shit Sherlock, that's the whole point. I could understand this from someone who has never attended university lectures, but it's surprising to see from Mehdi.
Really, the eye opener should be the fact that "correct probing" requires carefully thought out geometric constructions. This is not what I mean when I, as a practical engineer, talk about correct probing. For me, correct probing means avoiding extra loop caused by the scope's ground clip, instead using the small springy thing to connect to the terminals of the small output capacitor, for example, directly. But this is only possible if the thing to be measured is a small physical point (like a 0805 capacitor). In other words: a lumped circuit, or a close approximation of it! If you are measuring between wide area of circuit, under influence of external field, then obviously the presence of leads cannot be avoided in any way. They become parts of the circuit. The definition that "correct probing" is the one that happens to give consistent results per equivalent circuit + KVL is of course backwards. We should use capable enough models so they can model the real world, not the other way around (constraint the real world until it matches with the simple model), because latter limits out capability of building useful circuits. We can do better.
If you don't know how to use KVL, it doesn't mean that KVL doesn't work!
If you don't know how to use KVL, it doesn't mean that KVL doesn't work!Look at it this way: Lewin has shown an experiment where clearly the measured outcome doesn't match with KVL. This is undisputed. You guys are spending great effort in building significantly different experiments (to the point they look something completely else even to a plumber's or carpenter's eye) that shows that in these experiments, KVL holds. Yet when suggested to add small modifications to the experiments, you won't do it.
Except that the measured outcome of Lewin's experiment DOES match KVL calculations! Just draw the correct equivalent circuit, solve, and presto: the KVL solution matches experimental measurements!!! Maybe I am pointing out the obvious, but if you don't solve the correct circuit you'll get an incorrect answer.
2) This circuit has been solved correctly in electromagnetics textbooks by experts in the field.
A consequence of Faraday’s law of induction is that Kirchhoff’s loop rule (which states that [integral]E · ds = 0 around a closed path) is no longer valid in situations where there is a changing magnetic field. Faraday has taken us beyond the comfortable realm of conservative electric fields. The voltage difference between two points now depends on the path between them. Problem 7.4 provides an instructive example of this fact.
3) Both Jesse and I have done experiments that demonstrate that KVL and measurements results match perfectly. Just need to be carefull when measuring.
4) Many people have debunked Lewin's claims, including Mehdi, RDS accademy, and Mabilde. Neither Jesse nor I are the first ones.
QuoteA consequence of Faraday’s law of induction is that Kirchhoff’s loop rule (which states that [integral]E · ds = 0 around a closed path) is no longer valid in situations where there is a changing magnetic field. Faraday has taken us beyond the comfortable realm of conservative electric fields. The voltage difference between two points now depends on the path between them. Problem 7.4 provides an instructive example of this fact.
Purcell & Morin, Electricity and Magnetism, 3rd Edition, Chapter 7.6
Check example 6.6 from Electromagnetics by Notaros. That is how Lewin's circuit should have been solved. Pay attention to Figure 6.10b where the equivalent circuit to be solved is correctly presented.
EDIT: " [integral]E · ds = 0 around a closed path" is not the general definition of KVL. KVL must include all EMFs, included magnetically induced EMFs. Says who you may ask? Maxwell himself!
Check example 6.6 from Electromagnetics by Notaros. That is how Lewin's circuit should have been solved. Pay attention to Figure 6.10b where the equivalent circuit to be solved is correctly presented.
EDIT: " [integral]E · ds = 0 around a closed path" is not the general definition of KVL. KVL must include all EMFs, included magnetically induced EMFs. Says who you may ask? Maxwell himself!
Soooo... the EMF is located on top of the resistors, it seems. Half just above R1, and half just above R2. How many centimeters, exactly? The text does not say. Can you locate with a bit more accuracy? No?
Or maybe...
Maybe that's the "equivalent circuit" that allows you to "solve the problem from the circuit theory point of view" and that is one of the introductory textbooks that do not explain clearly to their easily distracted audience what they intend for V. Oh, wait, but it does explain what V is! Page 269, eq. 6.18
Eq = - grad V
(Eq is what I call Ecoul) and V is... the electric scalar potential. Only half of the potentials required to describe the total electric field. And the text also says so explicitly on page 277, formula 6.43
E(t) = - dA/dt - grad V
"We see that both potentials are needed for E..."
(the same expression I used to express Etot = Eind + Ecoul, even if recently I decided to call the scalar electric potential phi, instead of V - exactly to avoid this kind of confusion you are having)
So...
where is exactly the EMF, again?
(Lewin problem is solved as an exercise on Purcell, Morin: Berkeley Physics vol 2, Electricity and Magnetism 3rd edition)
(Yes, I have checked with the kitchen. They do have deja-vus)
Also you did not answer my 2nd question: how one can practically demonstrate path-dependency using transformer with let's say, 100 turns of secondary.When you measure from the outside you can look at the measure in two ways:
the voltmeter shows the actual voltage in the gap between taps
the voltmeter shows the voltage along the portion of filament between the taps (which is the ohmic drop that is nearly zero volts) plus (or minus depedending on orientation) the linked emf (emf of one turn times integer number of turns linked).
Sorry, I do not see how this demonstrates path-dependency. Let's say - I measure 10VAC on 100-turn secondary of my transformer. Please tell how to set-up 2nd AC voltmeter that would demonstrate "path-dependency", measure 0VAC while connected to same terminals as 1st voltmeter measuring 10VAC? Do you agree that 100 turns of 2nd voltmeter test leads on transformer needed?
Lewin's team, please come down to the Earth and answer this simple question - about how to demonstrate path-dependency on real transformer with 100-turn secondary using two AC voltmeters one showing nominal AC volts, another 0V. Many will be pleased to discover something they do not know yet. [disclaimer] I am usually not that persistent, but I feel like Killer Question (© Sredni) has been asked.
Yes, the current question is always the killer question.
Until it gets answered. They it becomes the forgotten question.
And killer question n+1 makes it appearance.
Lewin's team, please come down to the Earth and answer this simple question - about how to demonstrate path-dependency on real transformer with 100-turn secondary using two AC voltmeters one showing nominal AC volts, another 0V. Many will be pleased to discover something they do not know yet. [disclaimer] I am usually not that persistent, but I feel like Killer Question (© Sredni) has been asked.
It didn't occur to you that university stuff is not supposed to be down to Earth. It's not supposed to be dumbed down and simplified. This is about the theoretical basis, which has to be understood when designing RF layouts, or when designing EM field solver simulators. Someone have to do those, even if you only buy a transformer or pre-certified RF module and use them within the datasheet conditions.
And indeed, designing an actual RF communication circuit would be a perfect example where Kirchoff laws do not apply. This is obvious to anyone seeing an antenna, a wire that goes nowhere, yet radiates energy out. Still, I'm sure if you try enough, you'll be able to somehow make use of Kirchoff laws by modeling the transmitter and receiver pair as a schematic. After all, you can use infinite number of circuit elements. But is it the right way?
If I understood your question right, one of the many possible answers to your question would be, by piercing through the possible packaging and looping the probe wire 100 turns around the core. This is completely unfruitful. No one uses Maxwell equations in everyday engineering with everyday off-the-shelf transformer, the whole idea of that component is that it performs as a lumped circuit, a black box.
This was never anyone's intention. You have been only fighting against made-up strawman for years. Come on! Let the academics do the academic discussion their way; the track record is excellent. We "practical engineers" should learn something about it, even if we don't go fully there. Forget the ego for a while.
Thing is, if you had some basic understanding of the matter, you'd know that your question is irrelevant to the matter.
Thing is, if you had some basic understanding of the matter, you'd know that your question is irrelevant to the matter.
Really? - Most pathetic excuse of no explanation ever seen. If you are not able to explain your "science" to your grandmother - you do not know it well enough.
Thing is, if you had some basic understanding of the matter, you'd know that your question is irrelevant to the matter.
Really? - Most pathetic excuse of no explanation ever seen. If you are not able to explain your "science" to your grandmother - you do not know it well enough.
I'm not spoonfeeding you. The answers you're looking for are all in this thread. There's no value in repeating them over and over.
I already answered to that specific question - by looping the measurement wire through the core -, but it doesn't prevent it being re-asked repeatedly, just like before.
These people are indeed like broken records. Or maybe you want to hear the answer from Sredni or bsfeechannel? Maybe I'm not qualified?
The key difference in Lewin's excercise and ogden's transformer circuit is that the former circuit is completely placed within the varying field, making it impossible to route the probe wires outside of the field.
The key difference in Lewin's excercise and ogden's transformer circuit is that the former circuit is completely placed within the varying field, making it impossible to route the probe wires outside of the field. The transformer? The field is contained within the core, and you can conveniently measure from the taps that are bought outside of the field.
As soon as Lewin's followers agree
that path-directivity can be proven
Summarizing a bit:
4) Many people have debunked Lewin's claims, including Mehdi, RDS accademy, and Mabilde. Neither Jesse nor I are the first ones.
If you don't know how to use KVL, it doesn't mean that KVL doesn't work!
This is incredibly sad. I may have overestimated the EEVBlog forum community quality.
[...]
Now I have realized how mediocre "practical engineers" can be totally manipulated into participating such needless and ridiculous war against science and education. Incredibly sad.
[...]
So get off the high horse and read, read, and reread until you understand. I'm not the only one who did full 180 and needed to apologize. It's not easy.
The key difference in Lewin's excercise and ogden's transformer circuit is that the former circuit is completely placed within the varying field, making it impossible to route the probe wires outside of the field. The transformer? The field is contained within the core, and you can conveniently measure from the taps that are bought outside of the field.
Actually, no. The probe wires are all outside of the magnetic flux region in Dr. Lewins experiment.
"Path-directivity", he said.I am not natural englisch speaker, also you most likely got what I did mean by saying so, but instead of just correcting, you did not miss opportunity to insult, again.
Man, come on. Stop it. You're not fooling anyone. You don't know the theory, nor the practice, and not even the terminology, because you don't know jack squat what it means.
Summarizing a bit:
4) Many people have debunked Lewin's claims, including Mehdi, RDS accademy, and Mabilde. Neither Jesse nor I are the first ones.
What you didn't say is that Mehdi, RDS, Mabilde and Jesse debunk each other. Mehdi said Lewin measured two different voltages across the same two points of the circuit due to bad probing. Mabilde said it was not bad probing, contradicting Mehdi, but it is because there's a "hidden" EMF in the probes. The RDS guy said the problem is otherwise: the ohm's law, according to him, predicts the presence of a voltage across a static wire that's not the product of its current times its resistance. Contradicting Mehdi and Mabilde. Jesse, the poor bugger, doesn't even have a theory to contradict the others, so he doesn't know what is really at stake, nor what to look for, nor how to interpret the results of his "experiment".
In common, all of the above showed without any doubt that, yes, voltages around a circuit immersed in a varying magnetic field are path-dependent. Jesse's setup even shows that dynamically. He changes the position, i.e. the path, of the hands of his clock and the meter displays a different voltage every time.QuoteIf you don't know how to use KVL, it doesn't mean that KVL doesn't work!
No one said KVL doesn't work. Sometimes it works. Sometimes it doesn't. It works when there's no varying magnetic field inside the area delimited by the boundaries of the circuit, and doesn't work otherwise.
You are definitively delusional! Mehdi, Bob Duhamel, Mabilde, Jesse, and I agree without contradiction among other things, that Lewin didn't probe the circuit correctly. This 'straw man' you are trying to create only highlights your deep ignorance about this subject matter. Lewin does say KVL doesn't work in the particular experiment that concerns us. But indeed KVL works as I have demonstrated may times already.
You are definitively delusional! Mehdi, Bob Duhamel, Mabilde, Jesse, and I agree without contradiction among other things, that Lewin didn't probe the circuit correctly. This 'straw man' you are trying to create only highlights your deep ignorance about this subject matter. Lewin does say KVL doesn't work in the particular experiment that concerns us. But indeed KVL works as I have demonstrated may times already.
The only thing you agree with is that Lewin is, according to you, wrong, but none of you agree exactly why. And your experiments exhibit exactly the same outcome of Lewin's experiment: it is possible to measure two different voltages at the same time across the same two points of a circuit subjected to a varying magnetic field inside the area delimited by its borders. In none of your experiments you could measure exactly the same voltage for any position of the probes or the meters.
So ¯\_(ツ)_/¯
I am not natural englisch speaker,
also you most likely got what I did mean by saying so
, but instead of just correcting, you did not miss opportunity to insult, again.
I am not natural englisch speaker,
No excuse. You had plenty of time to understand what the path-dependence of voltage means because you have been exposed to this concept for quite a few years now.Quotealso you most likely got what I did mean by saying so
We have corrected you multiple times and you refused to accept the correction. Why would you accept it now?Quote, but instead of just correcting, you did not miss opportunity to insult, again.
Ignorance is a moral issue. Don't blame me for yours.
1) What is the calculated voltage between nodes A and D, VAD, in Lewin's circuit?
Ignorance is a moral issue. Don't blame me for yours.
1) What is the calculated voltage between nodes A and D, VAD, in Lewin's circuit?
We have heard this "question" so many times I think we are reaching a situation which could be considered spam, forbidden by the forum rules. Basically copy-pasting your arguments is not helpful to anyone.
You have been given calculated values many times in this thread, also reasoning behind the numbers. It seems clear you just don't like the answer, or agree with it. Which is fine. But...
Now with sensible adults, discussion goes like this:
1 You ask X
2 You get answered
3 You don't agree
4 You tell why you don't agree so discussion can go on
5a In the end, either you accept being wrong, or you are right. Somebody learns something;
or
5b There is no resolution. End of story. No endless loop. Everybody can go do something else.
Not this:
1 You ask X
2 You get answered
3 You don't agree
4 goto 1, infinitely, word for word. + use the fact that others do not participate in your sick game and copy-paste their answers, as some kind of proof for a victory dance.
I see this as borderline harassment, nothing else. This is not only embarrassing because it's so obvious, but I'm sure everybody feels bad, yourself included, no? Please consider stopping this behavior and start behaving like a decent human being, accepting the fact that you are in disagreement, but trying to go forward.
1) What is the calculated voltage between nodes A and D, VAD, in Lewin's circuit?
We have heard this "question" so many times I think we are reaching a situation which could be considered spam, forbidden by the forum rules. Basically copy-pasting your arguments is not helpful to anyone.
You have been given calculated values many times in this thread, also reasoning behind the numbers. It seems clear you just don't like the answer, or agree with it. Which is fine. But...
Now with sensible adults, discussion goes like this:
1 You ask X
2 You get answered
3 You don't agree
4 You tell why you don't agree so discussion can go on
5a In the end, either you accept being wrong, or you are right. Somebody learns something;
or
5b There is no resolution. End of story. No endless loop. Everybody can go do something else.
Not this:
1 You ask X
2 You get answered
3 You don't agree
4 goto 1, infinitely, word for word. + use the fact that others do not participate in your sick game and copy-paste their answers, as some kind of proof for a victory dance.
I see this as borderline harassment, nothing else. This is not only embarrassing because it's so obvious, but I'm sure everybody feels bad, yourself included, no? Please consider stopping this behavior and start behaving like a decent human being, accepting the fact that you are in disagreement, but trying to go forward.
Do you know why I keep asking? Because if you answer it correctly then you'll admit that KVL works in Lewin's circuit, which is the topic of this forum.
So, see if you can calculate VAD and then measure VAD and they match... So start by calculating VAD first, then we can talk.
1) What is the calculated voltage between nodes A and D, VAD, in Lewin's circuit?
It.
Depends.
On.
The.
Path.
Here are a few paths for which VAD, which I call VBA, has the value +0.9V.
Among this paths there are the left circuit branch and the path composed by probes and left voltmeter.
(https://i.postimg.cc/sDY8LD67/voltages-on-the-left.jpg)
Yes, it depends on the path of the circuit formed by the wires and components. An unique path that is not changing geometry or moving throughout space. The dashed paths you drew in the figure above are not valid paths because they are incapable of circulating current; they are made of... air? You can not apply Faraday's law or more generally KVL on those made up paths. The line integral must follow the circuit. At this point you are even in conflict with what is correct in Lewin's lectures. It is a waste of time to argue with you on anything else when you can not grasp this very simple concept.
Yes, it depends on the path of the circuit formed by the wires and components. An unique path that is not changing geometry or moving throughout space. The dashed paths you drew in the figure above are not valid paths because they are incapable of circulating current; they are made of... air? You can not apply Faraday's law or more generally KVL on those made up paths. The line integral must follow the circuit. At this point you are even in conflict with what is correct in Lewin's lectures. It is a waste of time to argue with you on anything else when you can not grasp this very simple concept.
:palm:
Don't let your ignorance of the concept itself of voltage hinder you.
Show us the values for the voltages across the resistors and across the probes in the above asymmetric and offcentered Lewin ring.
All paths are made of copper, resistive material and voltmetrium. All in matter, the way you like.
Now, please, tell us what those values are.
Time to put up or shut up.
Back to Lewin's circuit which is perfectly symmetric, with no extra 'dashed' paths. Let us concentrate on that fixed circuit, with no extra wires of any kind. If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
Lewin's cultists suddenly ignore Faraday's law of Electromagnetic Induction
Lewin's cultists suddenly ignore Faraday's law of Electromagnetic Induction
There are two kinds of people here: those who, in the words of Siwastaja, "get off the high horse and read, read, and reread until you understand", and those who are too lazy to learn electromagnetism and think that attacking those who can teach it will redeem them from their profound stupidity.
Nope! There is also bsfeechannel, a fine example of the Dunning-Kruger effect.
If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
As you are claiming that this is recursive - you shall not have any difficulties of finding post with answer to this ever repeating question.
As you are claiming that this is recursive - you shall not have any difficulties of finding post with answer to this ever repeating question.
Oh, now I see the tactic clearly.
Now, please, tell us what those values are.
Time to put up or shut up.
What you are trying to do here is the good old "moving-the-goalposts" fallacy. You are trying to distract from the original question; your plan is not going to work.
Back to Lewin's circuit which is perfectly symmetric, with no extra 'dashed' paths. Let us concentrate on that fixed circuit, with no extra wires of any kind. If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
Yes I was expecting to continue discussion with Sredni or bsfeechannel, not you. As soon as Lewin's followers agree that path-dependency can be proven using multiple windings of measurement wire which are essentially another secondary winding on transformer
Now, please, tell us what those values are.
Time to put up or shut up.
What you are trying to do here is the good old "moving-the-goalposts" fallacy. You are trying to distract from the original question; your plan is not going to work.
Back to Lewin's circuit which is perfectly symmetric, with no extra 'dashed' paths. Let us concentrate on that fixed circuit, with no extra wires of any kind. If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
You remind me of that guy who claimed he could read.
But he could only read from his own only book. Not other books.
Hic Rhodus, hic salta.
What happened to your beautiful theory? It only applies to circular concentric setups?
What I described applies to any circuit! It may not be easy but it is doable! I will not be distracted with a harder problem because that is your tactic. Let us concentrate in easy symmetric setups like Lewin's circuit, the one where he says KVL doesn't work. Did you figure out how to calculate VAD yet? You may want to read the post from Ogden, he explains it clearly, and it is very easy.
Apparently he figured it out. Here: https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927425/#msg3927425 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927425/#msg3927425)
Can you explain us where is his calculation wrong?
I have seen Ogden's calculations, but such calculation relies heavily on symmetry. Albeit knowing that it may be harder, how is that calculation applied to a non symmetric circuit?
Regards.
There is only one answer. The voltage VAD is unique, because there is only one path to consider, the path of the circuit.
Then how will you measure such VAD?The real question here should be: will KVL work on an loop that is not circular with an asymmetrically placed magnetic flux? Of course it will! That is what Faraday's law tell us.
Then how will you calculate VAD in an asymmetrical circuit?
Yes I was expecting to continue discussion with Sredni or bsfeechannel, not you. As soon as Lewin's followers agree that path-dependency can be proven using multiple windings of measurement wire which are essentially another secondary winding on transformer
But are they?
The other winding has the voltmeter's internal resistance embedded into it. Do you really think it is equivalent to another secondary winding of a transformer?
Back to the voltage between A-D: If circuit is symmetric, all four wires of the circuit loop equal length, resistors so small that we ignore EMF inside them, then each wire receives 1/4 of EMF, 1V/4 = 0.25V. Voltage between A and D will be +0.25V-0.1V+0.25V = 0.4V if calculated using 100 Ohm resistor side. Also we can calculate voltage using 900 Ohm resistor side, -0.25+0.9V-0.25=0.4V.How would you compute Vad if:
- the circuit is not symmetric;
- and the four wires have different lengths.
And also, how will you measure Vad (supposed that it is even possible to directly measure it)?
Now, please, tell us what those values are.
Time to put up or shut up.
What you are trying to do here is the good old "moving-the-goalposts" fallacy. You are trying to distract from the original question; your plan is not going to work.
Back to Lewin's circuit which is perfectly symmetric, with no extra 'dashed' paths. Let us concentrate on that fixed circuit, with no extra wires of any kind. If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
You remind me of that guy who claimed he could read.
But he could only read from his own only book. Not other books.
Hic Rhodus, hic salta.
What happened to your beautiful theory? It only applies to circular concentric setups?
What I described applies to any circuit! It may not be easy but it is doable!
I will not be distracted with a harder problem because that is your tactic.
Let us concentrate in easy symmetric setups like Lewin's circuit, the one where he says KVL doesn't work. Did you figure out how to calculate VAD yet?
By the way, where are the calculations for the two capacitor problem? It looks to me that you used SPICE to solve that one. How did you represent the induced EMF in the equivalent circuit?
Now, please, tell us what those values are.
Time to put up or shut up.
What you are trying to do here is the good old "moving-the-goalposts" fallacy. You are trying to distract from the original question; your plan is not going to work.
Back to Lewin's circuit which is perfectly symmetric, with no extra 'dashed' paths. Let us concentrate on that fixed circuit, with no extra wires of any kind. If you assume the voltage between nodes A and D, VAD, is unique at some instant of time (which by the way it is true), can you calculate that voltage?
You remind me of that guy who claimed he could read.
But he could only read from his own only book. Not other books.
Hic Rhodus, hic salta.
What happened to your beautiful theory? It only applies to circular concentric setups?
What I described applies to any circuit! It may not be easy but it is doable!
Oh, I know it is doable. Numerically. And Notaros, McDonald and Belcher know how to do it, as well.
But I believe most KVLers have no friggin' idea on how to do it.
Can you do it?QuoteI will not be distracted with a harder problem because that is your tactic.
No, my tactic is to show you that the EM method of using both the electrical scalar potential and the magnetic vector potential is not the brightest of the ideas when you are dealing with circuits. And if you were able to solve that problem you would know what Notaros and McDonald mean. And I could also show you how you do NOT use this method in every day life.QuoteLet us concentrate in easy symmetric setups like Lewin's circuit, the one where he says KVL doesn't work. Did you figure out how to calculate VAD yet?
See? I showed you so many VAD so many times that I've lost count. And you still pretend I didn't.QuoteBy the way, where are the calculations for the two capacitor problem? It looks to me that you used SPICE to solve that one. How did you represent the induced EMF in the equivalent circuit?
Do you really think it's that difficult to compute the reactances and use those instead of resistances?
Wow. To me, it's so easy it's basically a waste of time doing it.
But I will do it when you show me what are the actual voltages across the resistors and the probe wires in the circuit I've drawn.
Can't you do it?
I do not see you are answering my question which was very SPECIFIC - about transformer with 100 turns of secondary winding. Also if you use voltmeter leads with resistance embedded into them - stop doing that! Get proper tools.
[edit] Same fallacy again and again. :palm: You can't draw mythical dotted line which separates circuit wires from probe wires and claim that Faradays's law of Induction stops where you choose:
(https://i.postimg.cc/zftL0ZHK/screenshot-4.png)
Seems you missed this:
https://www.eevblog.com/forum/amphour/562-electroboom!/msg3913808/#msg3913808 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3913808/#msg3913808)
Are those the zero internal resistance voltmeters?
This video from Trevor Kearney debunks many, if not all your claims:
https://www.youtube.com/watch?v=FR8k12j7_Eo (https://www.youtube.com/watch?v=FR8k12j7_Eo)
Have you watched it yet? Pay attention on how many potential difference voltages between nodes A and B he calculates: one.
This video from Trevor Kearney debunks many, if not all your claims:
https://www.youtube.com/watch?v=FR8k12j7_Eo (https://www.youtube.com/watch?v=FR8k12j7_Eo)
Have you watched it yet? Pay attention on how many potential difference voltages between nodes A and B he calculates: one.
This is the second time I write this in this thread.
Dude, that's Trevor Kearney. He's probably the most active "Lewin defender" on youtube (go read his posts on Electroboom's channel if you don't believe me). He's "Armchair Physics Nobel Laureate" number one in fromjesse's scale. It's funny that you bring his videos in your defense (like fromjesse linking those videos from Purdue university, not understanding that professor Melloch has the same views as Lewin).
Trevor is computing the ELECTRIC SCALAR POTENTIAL difference. One of the two components of the actual voltage.
And, no, in the case of my wobbly circuit, not even him will be able to find a closed analytical solution. You have to go numerical. But that's not the point. The point is that you are not able to find 'your' voltage between any two points of a simple resistive circuit linking a variable magnetic flux. Not a very useful theory, isn't it. Especially considering that you should apply that even to simple resistive circuits NOT linking a variable magnetic flux, but just being in the same universe as a variable magnetic flux region. (Let me guess: you have no idea what I am talking about, right?)
ADDENDUM
Yes, I really meant "zero internal resistance voltmeters" because I did consider the 10 meg internal resistance of my voltmeter when I showed you that running a voltmeter with its probes around a magnetic core is NOT the same thing as running a zero resistance wire around it. But you did not understand that either
Same fallacy again and again. :palm: You can't draw mythical dotted line which separates circuit wires from probe wires and claim that Faradays's law of Induction stops where you choose:
(https://i.postimg.cc/zftL0ZHK/screenshot-4.png)
You do not understand what you see. Any path you can imagine within that region of space will NOT be able to form a loop (with the branch of circuit you want to measure the voltage of) that will cut the variable flux. That is why KVL will work in that region of space.
In 2D it's easy to see it. In 3D the three-dimensional region of space will be more complicated, but you can still find it.
Same fallacy again and again. :palm: You can't draw mythical dotted line which separates circuit wires from probe wires and claim that Faradays's law of Induction stops where you choose:
(https://i.postimg.cc/zftL0ZHK/screenshot-4.png)
You do not understand what you see. Any path you can imagine within that region of space will NOT be able to form a loop (with the branch of circuit you want to measure the voltage of) that will cut the variable flux. That is why KVL will work in that region of space.
In 2D it's easy to see it. In 3D the three-dimensional region of space will be more complicated, but you can still find it.
So you say that circuit containing just open wire loop which you drew around variable flux area is subject of Faraday's law of induction, but probe leads which also you drew around variable flux area, just farther away than wire - do not? This is yes/no question.
So you say that circuit containing just open wire loop which you drew around variable flux area is subject of Faraday's law of induction, but probe leads which also you drew around variable flux area, just farther away than wire - do not? This is yes/no question.
It may surprise you, but the answer to this would actually be: no. :-DD
And still the volt meter would read 0V.
Lewin's cultists truly believe that 1/4 of the transformer wire turn do not have 1/4 of EMF on it because when they try to measure using voltmeter, by placing voltmeter leads next to wire they measure, they see 0V - as expected.
It is obvious that Faradays' law of induction do not care - it is test circuit or voltmeter leads, but Lewin's cultists are stubborn, they claim that they know better and for some reason voltmeter leads are not influenced by time-varying magnetic field of experiment, only circuit.
In short - fact that Lewin and his cultists struggle to properly measure EMF, do not mean it does not exist.
QuoteIn short - fact that Lewin and his cultists struggle to properly measure EMF, do not mean it does not exist.
We, you and all the other cabrones like Mehdi, Mabilde, Jesse and the RSD dude, measure and the voltage is zero (or to be precise it is the current times the resistance of the wire), exactly like the theory predicts.
Does KVL hold? Yes!
\$ - 0.3798V + 0.1A \times 5\Omega + 0.1A \times 5\Omega - 0.6202V = 0 \$
What BS excuse are you going to craft now?
The theory of conjugate conductors has been investigated by
Kirchhoff, who has stated the conditions of a linear system in
the following manner, in which the consideration of the potential
is avoided.
(1) (Condition of 'continuity.') At any point of the system
the sum of all the currents which flow towards that point is
zero.
(2) In any complete circuit formed by the conductors the sum
of the electromotive forces taken round the circuit is equal to
the sum of the products of the current in each conductor multi-
plied by the resistance of that conductor.
It is always worth reminding ourselves that our voltmeter connected between nodes A and B, and the conditions are that the voltmeter measurement PATH does not intersect the time varying field, the voltmeter will not indicate the potential difference between A and B, rather it will indicate the OHMIC voltage difference between nodes A and B.
Does KVL hold? Yes!
\$ - 0.3798V + 0.1A \times 5\Omega + 0.1A \times 5\Omega - 0.6202V = 0 \$
What BS excuse are you going to craft now?
How about the one given by Maxwell?QuoteThe theory of conjugate conductors has been investigated by
Kirchhoff, who has stated the conditions of a linear system in
the following manner, in which the consideration of the potential
is avoided.
(1) (Condition of 'continuity.') At any point of the system
the sum of all the currents which flow towards that point is
zero.
(2) In any complete circuit formed by the conductors the sum
of the electromotive forces taken round the circuit is equal to
the sum of the products of the current in each conductor multi-
plied by the resistance of that conductor.
So, if the consideration of potential is avoided, then we need to eliminate the potential difference between points A and D from your beautiful equation, which becomes:
\$ 0.1A \times 5\Omega + 0.1A \times 5\Omega = 1V ≠ 0 \$
KVL fails.
And this agrees exactly with what he says in the video @12:19:QuoteIt is always worth reminding ourselves that our voltmeter connected between nodes A and B, and the conditions are that the voltmeter measurement PATH does not intersect the time varying field, the voltmeter will not indicate the potential difference between A and B, rather it will indicate the OHMIC voltage difference between nodes A and B.
This video from Trevor Kearney debunks many, if not all your claims:
https://www.youtube.com/watch?v=FR8k12j7_Eo (https://www.youtube.com/watch?v=FR8k12j7_Eo)
Have you watched it yet? Pay attention on how many potential difference voltages between nodes A and B he calculates: one.
This is the second time I write this in this thread.
Dude, that's Trevor Kearney. He's probably the most active "Lewin defender" on youtube (go read his posts on Electroboom's channel if you don't believe me). He's "Armchair Physics Nobel Laureate" number one in fromjesse's scale. It's funny that you bring his videos in your defense (like fromjesse linking those videos from Purdue university, not understanding that professor Melloch has the same views as Lewin).
Trevor is computing the ELECTRIC SCALAR POTENTIAL difference. One of the two components of the actual voltage.
And, no, in the case of my wobbly circuit, not even him will be able to find a closed analytical solution. You have to go numerical. But that's not the point. The point is that you are not able to find 'your' voltage between any two points of a simple resistive circuit linking a variable magnetic flux. Not a very useful theory, isn't it. Especially considering that you should apply that even to simple resistive circuits NOT linking a variable magnetic flux, but just being in the same universe as a variable magnetic flux region. (Let me guess: you have no idea what I am talking about, right?)
ADDENDUM
Yes, I really meant "zero internal resistance voltmeters" because I did consider the 10 meg internal resistance of my voltmeter when I showed you that running a voltmeter with its probes around a magnetic core is NOT the same thing as running a zero resistance wire around it. But you did not understand that either
Really? It looks to me that you didn't watch the video! Are you in denial again? Here, I added to his right hand side circuit equivalent, the equivalent circuit for the left hand side:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1374995;image)
Let us calculate the voltage from the right:
\$V_{AB} = 0.3798V - 0.1A \times 5\Omega = - 0.1202V\$
Now the voltage from the left:
\$V_{AB} = 0.1A \times 5\Omega - 0.6202V = - 0.1202V\$
Are the calculated values identical? Yes!
Does KVL hold? Yes!
\$ - 0.3798V + 0.1A \times 5\Omega + 0.1A \times 5\Omega - 0.6202V = 0 \$
What BS excuse are you going to craft now?
Well, it means that if you measure with the voltmeter without cancelling the induced EMF in the probes due to the varying magnetic field, what you read in the multimeter is the voltage drop in the resistance. This is the mistake that Lewin made in his demonstration. But wait, there is more:
3) Starting at minute 13:00 Trevor Kearney says : "...if it were physically possible to align a voltmeter measurement path with the physical path A-X-B, the indication would then be the same as the calculated potential difference...". Do you know why?
Because there will not be induced EMF in the voltmeter probes!
This is exactly what I have shown a bunch of times with my experiments.
And this is also what Lewin failed to do or even understand in his experiment.
Oh, now I see the tactic clearly.
This video from Trevor Kearney debunks many, if not all your claims:
https://www.youtube.com/watch?v=FR8k12j7_Eo (https://www.youtube.com/watch?v=FR8k12j7_Eo)
Have you watched it yet? Pay attention on how many potential difference voltages between nodes A and B he calculates: one.
This is the second time I write this in this thread.
Dude, that's Trevor Kearney. He's probably the most active "Lewin defender" on youtube (go read his posts on Electroboom's channel if you don't believe me). He's "Armchair Physics Nobel Laureate" number one in fromjesse's scale. It's funny that you bring his videos in your defense (like fromjesse linking those videos from Purdue university, not understanding that professor Melloch has the same views as Lewin).
Trevor is computing the ELECTRIC SCALAR POTENTIAL difference. One of the two components of the actual voltage.
And, no, in the case of my wobbly circuit, not even him will be able to find a closed analytical solution. You have to go numerical. But that's not the point. The point is that you are not able to find 'your' voltage between any two points of a simple resistive circuit linking a variable magnetic flux. Not a very useful theory, isn't it. Especially considering that you should apply that even to simple resistive circuits NOT linking a variable magnetic flux, but just being in the same universe as a variable magnetic flux region. (Let me guess: you have no idea what I am talking about, right?)
ADDENDUM
Yes, I really meant "zero internal resistance voltmeters" because I did consider the 10 meg internal resistance of my voltmeter when I showed you that running a voltmeter with its probes around a magnetic core is NOT the same thing as running a zero resistance wire around it. But you did not understand that either
Really? It looks to me that you didn't watch the video! Are you in denial again? Here, I added to his right hand side circuit equivalent, the equivalent circuit for the left hand side:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1374995;image)
Let us calculate the voltage from the right:
\$V_{AB} = 0.3798V - 0.1A \times 5\Omega = - 0.1202V\$
Now the voltage from the left:
\$V_{AB} = 0.1A \times 5\Omega - 0.6202V = - 0.1202V\$
Are the calculated values identical? Yes!
Does KVL hold? Yes!
\$ - 0.3798V + 0.1A \times 5\Omega + 0.1A \times 5\Omega - 0.6202V = 0 \$
What BS excuse are you going to craft now?
Ok, I had not watched the video, because I cannot see images and videos from my laptop. Now I logged in (for the first time) with my phone and while posting is a PITA (is this why you quote entire posts? Can't select parts of text?), at least I can see videos and images to the posts I respond.
Yes, if you take A UNIFORM RESISTIVE RING the voltages you measure from the exterior between two points on a diameter are bound to be equal because they are given by
Resistance of arc * current in loop
And if the arcs have the same length you end up with the same voltage. The flux off axis requires the development of surface charge that will compensate for the nonuniformity of the induced field in the region occupied by the ring.
This is not the two resistor lewin ring but it's okay, I'll go along with it.
Now PICK TWO POINTS THAT ARE NOT ON A DIAMETER, and show us how KVL is working.
For example pick A and B such that going from A to B will require three quarter of circumference and going from B to A will require a quarter.
Compute the voltages now.
Faraday's law of induction doesn't care about wires, leads, probes, whatever. They're irrelevant. They're not even mentioned in the law.
Faraday's law states that there is emf on the conductive loop when the magnetic flux through the surface enclosed by the loop varies in time.
Lewin's cultists truly believe that 1/4 of the transformer wire turn do not have 1/4 of EMF on it because when they try to measure using voltmeter, by placing voltmeter leads next to wire they measure, they see 0V - as expected.
If, as expected, the voltage measured across a piece of wire is zero, it is because it IS zero. Any other conjecture about that voltage is absolutely moronic in the context of our discussion.QuoteIt is obvious that Faradays' law of induction do not care - it is test circuit or voltmeter leads, but Lewin's cultists are stubborn, they claim that they know better and for some reason voltmeter leads are not influenced by time-varying magnetic field of experiment, only circuit.
Faraday's law of induction doesn't care about wires, leads, probes, whatever. They're irrelevant. They're not even mentioned in the law.
What Faraday's law of induction says is that the TOTAL EMF around a CLOSED ARBITRARY path, any path, whatever path in whatever portion of the SPACE, is proportional to the rate of change of the magnetic field INSIDE the area, whatever area, delimited by the aforementioned closed PATH.
So, if your meter, your probes and your wire under test constitute a closed PATH that delimit an AREA where the magnetic field doesn't change or, better yet, where there's none, the EMF is NULLE (in Latvian), i.e. ZERO, нуль, صفر, 零, μηδέν.
So there's no EMF, no belief, no cultism, no Lewin. It is only the theory, which by the way was extensively reviewed and tested by the most brilliant minds of our recent times, agreeing with practice.
Lewin, the Lewin cultism, the belief, and the phantasmagorical EMF that you claim is present in the wires is just an artificial construct that only exists in the brain-damaged mind of a KVLiar. No scientist, professor or author, dead or alive, will agree with you.QuoteIn short - fact that Lewin and his cultists struggle to properly measure EMF, do not mean it does not exist.
We, you and all the other cabrones like Mehdi, Mabilde, Jesse and the RSD dude, measure and the voltage is zero (or to be precise it is the current times the resistance of the wire), exactly like the theory predicts.
I told you in the other discussion we had three years ago that you don't understand electromagnetism because you're a "circuity" guy. You're limited to wires. No wonder, Kirchhoff was obsessed with them. They're the essence of his laws. Maxwell's equations made us understand the phenomenon of electricity and magnetism beyond wires. The universe is plenty of an unfathomably large number of electromagnetic events and it is not even wired.
So free your mind and give Lewin a kiss in the cheek.
Now everybody can see what cultism does to the brain. He states:Faraday's law of induction doesn't care about wires, leads, probes, whatever. They're irrelevant. They're not even mentioned in the law.
Actual law:QuoteFaraday's law states that there is emf on the conductive loop when the magnetic flux through the surface enclosed by the loop varies in time.
If that is not conclusive enough, one can watch Dr.Lewin's YT video about Faraday's law (https://youtu.be/nGQbA2jwkWI?t=1).
Now everybody can see what cultism does to the brain.
Actual law:
Faraday's law states that there is emf on the conductive loop when the magnetic flux through the surface enclosed by the loop varies in time.
If that is not conclusive enough, one can watch Dr.Lewin's YT video about Faraday's law (https://youtu.be/nGQbA2jwkWI?t=1).
Whole post for the records, in case bsfeechannel wakes-up
and finds that he contradicted even to himself:
QuoteCompute the voltages now.
Sure, why not. I picked the nodes A and C as shown in the figure:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1375328;image)
Since the circuit is symmetric along the horizontal axis with respect to the magnetic flux, the induced EMF between nodes A and C on the top right quarter is half what Trevor Kearney calculated in the video, or 0.3798V/2=0.1899V. Also the resistance is now also half or 2.5 ohms. Conversely, the induced EMF in the rest of the ring is 1V-0.1899V=0.8101V and the resistance is 7.5 ohms
I never sleep.
QuoteCompute the voltages now.
Sure, why not. I picked the nodes A and C as shown in the figure:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1375328;image)
Since the circuit is symmetric along the horizontal axis with respect to the magnetic flux, the induced EMF between nodes A and C on the top right quarter is half what Trevor Kearney calculated in the video, or 0.3798V/2=0.1899V. Also the resistance is now also half or 2.5 ohms. Conversely, the induced EMF in the rest of the ring is 1V-0.1899V=0.8101V and the resistance is 7.5 ohms
That is not voltage. That is scalar potential difference.
It turns out that Trevor uses V to denote the scalar potential difference (what I now call phi) and U_path to denote voltage (what I call V_gamma).
You can ask himself, if you want.
Comment in his video asking:
"Hi Trevor, is this video a demonstration that Lewin is wrong in saying that voltage is path dependent? Or are you computing the scalar potential difference which happens to be independent of path, but is different from voltage?"
And see what he replies.
Chances are that he will link you to his last video "Scalar potential difference a questionable choice for the true voltage between the test nodes in Dr Lewin's Experiment"
https://www.youtube.com/watch?v=I1kYKF2x9Ns (https://www.youtube.com/watch?v=I1kYKF2x9Ns)
(In case you are wondering, no I haven't seen all of Trevor's videos from start to finish. I love his passion and I know we share the same positions from what he writes in the comments on YouTube, bit his videos are too long and too low volume for me to watch from start to finish - I just skim through them. But here is a screenshot that tells the whole story:
(https://i.postimg.cc/cCR5wB1k/Trevor-s-PD-vs-Voltage.png)
see, how he makes a distinction between scalar potential difference and voltage?)
In that problem the scalar potential difference is equal to the true voltage between nodes A and C because the magnetic flux is defined as:
\$\varphi (t) = 1.0t[Wb]\$
So the magnitude of the induced EMF is a constant 1V, which is not a function of time. We are solving a DC circuit!
In that problem the scalar potential difference is equal to the true voltage between nodes A and C because the magnetic flux is defined as:
\$\varphi (t) = 1.0t[Wb]\$
So the magnitude of the induced EMF is a constant 1V, which is not a function of time. We are solving a DC circuit!
What does that have to do with anything? It's just a construct to make the calculation easier to follow.
I never sleep.
Brother!
So is my calculation of the potential difference between nodes A and C correct or no? Is that the voltage VAC or not? Just asking, because I see yet another 'moving the goalposts' fallacy coming from Sredni.
If you think that the scalar potential difference will save you, think again.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376111;image)
To prove that KVL is for birds, Lewin's cultists simply omit energy source in their circuit schematics - as if current is appearing out of nowhere.
Very clever! BTW 0.5V + 0.5V = 1V
To prove that KVL is for birds, Lewin's cultists simply omit energy source in their circuit schematics - as if current is appearing out of nowhere.
This is not a concern of KVL. It only states that the voltages around a loop must add up to zero. End of story. In the case of Lewin's circuit they don't.QuoteVery clever! BTW 0.5V + 0.5V = 1V
Which is even worse, since 1 V is farther away from 0 V than 0.5 V is.
To prove that KVL is for birds, Lewin's cultists simply omit energy source in their circuit schematics - as if current is appearing out of nowhere.
This is not a concern of KVL. It only states that the voltages around a loop must add up to zero. End of story. In the case of Lewin's circuit they don't.QuoteVery clever! BTW 0.5V + 0.5V = 1V
Which is even worse, since 1 V is farther away from 0 V than 0.5 V is.
Next thing Lewin's cultists do - choose convenient to their fallacy, polarities. They can easily claim that 1V chemical battery in series with 1K resistor sum-up to 2V because I*R added to 1V of the battery equals 2V, so KVL per their logic fail. :palm:
If you think that the scalar potential difference will save you, think again.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376111;image)
To prove that KVL is for birds, Lewin's cultists simply omit energy source in their circuit schematics - as if current is appearing out of nowhere. Very clever! BTW 0.5V + 0.5V = 1V which is voltage of "invisible EMF source", so... how to say... you did just prove KVL! Congrats! Glad you can learn too. Next time don't forget to include transformer secondary in your schematics. Hopefully you know the symbol.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376111;image)
So, if the scalar PD between A and D is the "true voltage" in the Lewin ring, then what @bsfeechannel showed above is a proper model for Dr. Lewins setup, right?
That means one can replace the induced EMF with a voltage source between A and D with the "true voltage" and that is then the energy source of the circuit?
But if this is really a proper model for Dr. Lewins circuit, it must also reproduce the meter readings from the experiment, right?
Only it doesn't. Hm. So, apparently it is not a proper model for Dr. Lewins circuit.
Maybe it's a proper model for the @jesuscf circuit? Apparently so, because he measured it with a few percent of error. He cannot say where this error comes from, but lets not go there now. But he also admits that if the probing wires were to follow a slightly different path, the error would increase.
So, @jesuscf found one single, very special path on which the \$V_{AD}\$ coincided with the computed scalar PD and yes, if in his circuit he replaced the induced EMF with a voltage source between A and D, the outcome would not change. But if he connected a second voltmeter between A and D on any other path, the whole model would collapse.
If you think that the scalar potential difference will save you, think again.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376111;image)
To prove that KVL is for birds, Lewin's cultists simply omit energy source in their circuit schematics - as if current is appearing out of nowhere. Very clever! BTW 0.5V + 0.5V = 1V which is voltage of "invisible EMF source", so... how to say... you did just prove KVL! Congrats! Glad you can learn too. Next time don't forget to include transformer secondary in your schematics. Hopefully you know the symbol.
...aaaaand we are back to square one.
5 + 3 = 8. Vs 5 + 3 - 8 = 0
and the inability of KVLers of seeing a difference between lumped and unlumpable circuits.
But hold that thought about current coming out of nowhere.
In the case of the perfectly symmetric uniform resistive ring we have Etot = Eind (this is exact in the 2D case). That is, since Ecoul=0, the scalar potential difference is zero everywhere on the ring.
And in fact KVLers proudly show that their radial measures of "voltage" are all zero.
In their view K"V"L holds because the sum of all zero "voltages" is zero.
But now its their turn to ignore the energy source.
They have all "voltages" zero, and "current coming out of nowhere". So they are forced to switch definition of voltage and invent the distributed battery+resistor element.
1-1+1-1+1-1+1-1+1-1+1-1+1-1+1-1=0
Does that mean that the radial measure that shows zero "voltage" is not measuring the true voltage, now?
I never sleep.
Brother!
Don't worry. I have a life.So is my calculation of the potential difference between nodes A and C correct or no? Is that the voltage VAC or not? Just asking, because I see yet another 'moving the goalposts' fallacy coming from Sredni.
If you think that the scalar potential difference will save you, think again.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376111;image)
So, if the scalar PD between A and D is the "true voltage" in the Lewin ring, then what @bsfeechannel showed above is a proper model for Dr. Lewins setup, right?No. It is just proper copy of Dr.Lewin's improper model which omits EMF source in the circuit schematics. Just because some could not find proof of EMF by
That means one can replace the induced EMF with a voltage source between A and D with the "true voltage" and that is then the energy source of the circuit?No. EMF is induced in the conductive elements of the loop. You can't calculate or measure voltage between two points of the circuit and declare it as voltage *source*. It could be just voltage *drop* with source somewhere else. You really shall consider to learn (more about) Electromagnetic Induction and Faraday's law, start with https://youtu.be/nGQbA2jwkWI?t=1 (https://youtu.be/nGQbA2jwkWI?t=1).
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
You don't understand how Faraday's law work! :-DD If the circuit formed by the probes of your instrument go around the 'confined' varying magnetic core, there is going to be an induced EMF in the probes unless you align the probes carefully.
That is what is happening in the video you posted; there is definitively an induced EMF in the oscilloscope probes. They are making exactly the same mistake Lewin made!
Watch this video from Trevor Kearney and pay attention to everything what he says. In particular, since you don't seem to understand how is done, look carefully how he derives the equivalent circuit for the RHS of the setup. That is what Lewin should have done.
https://youtu.be/FR8k12j7_Eo
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
You don't understand how Faraday's law work! :-DD If the circuit formed by the probes of your instrument go around the 'confined' varying magnetic core, there is going to be an induced EMF in the probes unless you align the probes carefully. That is what is happening in the video you posted; there is definitively an induced EMF in the oscilloscope probes. They are making exactly the same mistake Lewin made!
Watch this video from Trevor Kearney and pay attention to everything what he says. In particular, since you don't seem to understand how is done, look carefully how he derives the equivalent circuit for the RHS of the setup. That is what Lewin should have done.
https://youtu.be/FR8k12j7_Eo
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
Can you read? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647). Dr.Lewin frustrated himself with overcomplicated experiment, drew wrong conclusions out of measurement results. If you see someone making error - you immediately label him an idiot? Dr.Lewin is brilliant teacher with loads of educating videos, I suggested one for you as well.
What you KVLers keep missing is that this emf makes the charge in the probes move and accumulate at the voltmeter's internal resistance and the field that is generated by that charge will cancel the induced field in the probes. Leaving nearly nothing in the probes.
I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.Maybe you catch him out of context? Anyway I strongly disagree (https://youtu.be/77ZF50ve6rs?t=3) :)
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Here we go again. One of many fallacies of Lewin's cultists. Think about various values of R2, ranging from 900 Ohms till open (no resistor):
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Here we go again. One of many fallacies of Lewin's cultists. Think about various values of R2, ranging from 900 Ohms till open (no resistor):
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
You said you understood circuit theory. Then you should know how each loop (mesh) in a circuit is to be evaluated separately, to later sum up all contributions. So, in Dr. Lewins circuit there are three loops, only one of which encloses an area with time-varying magnetic flux. Or do you suddenly want to argue that circuit theory cannot be applied any more? But KVL still works?
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Here we go again. One of many fallacies of Lewin's cultists. Think about various values of R2, ranging from 900 Ohms till open (no resistor):
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
You said you understood circuit theory. Then you should know how each loop (mesh) in a circuit is to be evaluated separately, to later sum up all contributions. So, in Dr. Lewins circuit there are three loops, only one of which encloses an area with time-varying magnetic flux. Or do you suddenly want to argue that circuit theory cannot be applied any more? But KVL still works?
Could be good we first clear question I asked you in my previous post (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3933425/#msg3933425) because it lets you really question "three loops, only one of which encloses an area with time-varying magnetic flux", but it seems you just take it for a granted as usually true believers do. You are just believer or you can think too? Visualization attached for case 3.
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Here we go again. One of many fallacies of Lewin's cultists. Think about various values of R2, ranging from 900 Ohms till open (no resistor):
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
You said you understood circuit theory. Then you should know how each loop (mesh) in a circuit is to be evaluated separately, to later sum up all contributions. So, in Dr. Lewins circuit there are three loops, only one of which encloses an area with time-varying magnetic flux. Or do you suddenly want to argue that circuit theory cannot be applied any more? But KVL still works?
Could be good we first clear question I asked you in my previous post (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3933425/#msg3933425) because it lets you really question "three loops, only one of which encloses an area with time-varying magnetic flux", but it seems you just take it for a granted as usually true believers do. You are just believer or you can think too? Visualization attached for case 3.
What's that supposed to change? The loop formed by the voltmeter and R2 still doesn't enclose any time-varying magnetic flux. You'd just have to analyze the circuit a little differently, but the result would stay the same.
There is no EMF induced in the loops formed by the probe wires and the resistors they connect to, because the paths \$C_1, C_2\$ don't enclose the magnetic flux region. This is a claim anyone can easily verify: Just take your oscilloscope probe, connect the ground lead to the tip and move it around the core, see if you can pick up any significant EMF. Also, it would be quite miraculous how any induced EMF caused by "stray magnetic flux" would exactly make the two voltages reproduce the ratio between the resistors, to conveniently coincide with what is expected through Ohms law.
Here we go again. One of many fallacies of Lewin's cultists. Think about various values of R2, ranging from 900 Ohms till open (no resistor):
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
You said you understood circuit theory. Then you should know how each loop (mesh) in a circuit is to be evaluated separately, to later sum up all contributions. So, in Dr. Lewins circuit there are three loops, only one of which encloses an area with time-varying magnetic flux. Or do you suddenly want to argue that circuit theory cannot be applied any more? But KVL still works?
Could be good we first clear question I asked you in my previous post (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3933425/#msg3933425) because it lets you really question "three loops, only one of which encloses an area with time-varying magnetic flux", but it seems you just take it for a granted as usually true believers do. You are just believer or you can think too? Visualization attached for case 3.
What's that supposed to change? The loop formed by the voltmeter and R2 still doesn't enclose any time-varying magnetic flux. You'd just have to analyze the circuit a little differently, but the result would stay the same.
It was supposed to let you actually think. Please be so kind, spread your wisdom. If as you say wires of outer loop having R2 do not receive any EMF, then I am all ears of your little different analysis for case #3. I am sure many others will be interested to hear it as well.QuotePS: I found this video quite enlightening:You can't say that there is no EMF in the wires of outer loop, at the time time agreeing to this video! :-DD
https://youtu.be/OmlnGei1xo8 (https://youtu.be/OmlnGei1xo8)
What I say is that \$ \oint E \cdot dl = 0\$ for the measurement loop.Typical tactics of Lewin's team - distraction and/or goalpost shifting.
I wonder if Ogden is capable of computing and comparing the currents in the loop R1 R2 alone, in the loop R1 voltmeter alone and then in the full circuit with R1 R2 and the voltmeter.Sure. (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647) It's because I state that there is no outer loop which miraculously avoids EM induction so it does not matter - you put voltmeter or resistor on outside loop. I am sure you agree because recently stated that EMF is induced in outer wires as well.
Then please by all means
Compute them and compare the three cases
1. R1 = 100 Ohms and R2 = open circuit. Do you agree that EMF is induced in voltmeter leads? You shall. Because essentially there is no R2.
2. R1 = 100 Ohms and R2 = 900 Ohms. Now voltmeter leads miraculously do not get any EMF - as soon as you put resistor of *any* resistance closer to solenoid than Voltmeter?
3. What if you exchange R2 = 900 Ohms and voltmeter? Then what?
What I say is that \$ \oint E \cdot dl = 0\$ for the measurement loop.Typical tactics of Lewin's team - distraction and/or goalpost shifting.
So you are not able to compute the current in those three simple circuits?
I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.Maybe you catch him out of context? Anyway I strongly disagree (https://youtu.be/77ZF50ve6rs?t=3) :)
My question would be: do you really believe that Dr. Lewin is such a massive fool that he didn't understand that the volt meters (or oscilloscopes) he used and the paths they were connected through were part of the circuit?
Yes.
I strongly disagree with jesuscf in this regard. Hopefully now this is clear and you can stop to bring this up. Better watch some Dr.Lewin's video. [edit] Wait.. I already stated that Dr.Lewin is brilliant teacher yet you are trying to prove something :wtf:Hm.I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.Maybe you catch him out of context? Anyway I strongly disagree (https://youtu.be/77ZF50ve6rs?t=3) :)
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
Can you read? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647). Dr.Lewin frustrated himself with overcomplicated experiment, drew wrong conclusions out of measurement results. If you see someone making error - you immediately label him an idiot? Dr.Lewin is brilliant teacher with loads of educating videos, I suggested one for you as well.
I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4 (https://youtu.be/u6ud7JD0fV4)
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
You don't understand how Faraday's law work! :-DD If the circuit formed by the probes of your instrument go around the 'confined' varying magnetic core, there is going to be an induced EMF in the probes unless you align the probes carefully.
What you KVLers keep missing is that this emf makes the charge in the probes move and accumulate at the voltmeter's internal resistance and the field that is generated by that charge will cancel the induced field in the probes. Leaving nearly nothing in the probes.QuoteThat is what is happening in the video you posted; there is definitively an induced EMF in the oscilloscope probes. They are making exactly the same mistake Lewin made!
Sure. The MIT has always been a nest of incompetent physicists and engineers.
They should hire you, instead!QuoteWatch this video from Trevor Kearney and pay attention to everything what he says. In particular, since you don't seem to understand how is done, look carefully how he derives the equivalent circuit for the RHS of the setup. That is what Lewin should have done.
https://youtu.be/FR8k12j7_Eo (https://youtu.be/FR8k12j7_Eo)
Did you ask Trevor if he thinks Lewin is in error?
Are you afraid of asking?
Because I am pretty sure you are misunderstanding his point of view.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4 (https://youtu.be/u6ud7JD0fV4)
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
Look at that: KVL works again!!! :-DD
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4 (https://youtu.be/u6ud7JD0fV4)
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
You don't understand how Faraday's law work! :-DD If the circuit formed by the probes of your instrument go around the 'confined' varying magnetic core, there is going to be an induced EMF in the probes unless you align the probes carefully.
What you KVLers keep missing is that this emf makes the charge in the probes move and accumulate at the voltmeter's internal resistance and the field that is generated by that charge will cancel the induced field in the probes. Leaving nearly nothing in the probes.QuoteThat is what is happening in the video you posted; there is definitively an induced EMF in the oscilloscope probes. They are making exactly the same mistake Lewin made!
Sure. The MIT has always been a nest of incompetent physicists and engineers.
They should hire you, instead!QuoteWatch this video from Trevor Kearney and pay attention to everything what he says. In particular, since you don't seem to understand how is done, look carefully how he derives the equivalent circuit for the RHS of the setup. That is what Lewin should have done.
https://youtu.be/FR8k12j7_Eo (https://youtu.be/FR8k12j7_Eo)
Did you ask Trevor if he thinks Lewin is in error?
Are you afraid of asking?
Because I am pretty sure you are misunderstanding his point of view.
Why should I ask Trevor Kearney a question he has already answer in his videos? You should go and watch his videos and try to understand them! Once you have done that, you'll know for sure who is correct.
Also, do you remember that time you asked me if I had a toroid? Well, I have one now! This beauty just arrived:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376789;image)
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
Can you read? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647). Dr.Lewin frustrated himself with overcomplicated experiment, drew wrong conclusions out of measurement results. If you see someone making error - you immediately label him an idiot? Dr.Lewin is brilliant teacher with loads of educating videos, I suggested one for you as well.
I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.
I don't remember saying that. Can point me where I said it?
EDIT: I see it. You can interpret that in many ways, but I didn't say Lewin is an idiot. I just said 'yes' to your convoluted question. But anyhow, believe what you want, that doesn't change reality. Also, just for the record 'fool' != 'idiot'.
...
Nice job! Appreciate your work and dedication. Especially nice is 2*10K solution which could spark new controversy - because it is "inner loop" 8)
Meanwhile those who are not yet made their mind, can read detailed article about controversy, Do not miss to watch all the videos linked:
https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work (https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work)
For those who want to repeat experiment - many toroidal inductors out of your scrap box can be ok for the job.
Also, really bad taste in suggesting that Lewin's personal life could mean anything about the physics he discusses.
The only error Lewin committed in his videos are slips of the tongue regarding terminology.
Nice job! Appreciate your work and dedication. Especially nice is 2*10K solution which could spark new controversy - because it is "inner loop" 8)
Meanwhile those who are not yet made their mind, can read detailed article about controversy, Do not miss to watch all the videos linked:
https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work (https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work)
For those who want to repeat experiment - many toroidal inductors out of your scrap box can be ok for the job.
Look at that: KVL works again!!! :-DD
Yes. KVL holds for meshes I and II, because they do not encircle a varying magnetic flux anymore, but you created a third mesh and behold there KVL fails. Guess why. Besides, points A and D still exhibit different voltages as clearly shown by your meters, which means that along the closed path of R1 an R2, the voltages still do not add up to zero and KVL fails again.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376999;image)
Kirchhoff hates you.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
PS: before you go about bringing "stray magnetic flux" into the game again, watch this video maybe:
https://youtu.be/u6ud7JD0fV4 (https://youtu.be/u6ud7JD0fV4)
Ring core transformer, magnetic flux well confined inside the core. But the outcome is the same.
You don't understand how Faraday's law work! :-DD If the circuit formed by the probes of your instrument go around the 'confined' varying magnetic core, there is going to be an induced EMF in the probes unless you align the probes carefully.
What you KVLers keep missing is that this emf makes the charge in the probes move and accumulate at the voltmeter's internal resistance and the field that is generated by that charge will cancel the induced field in the probes. Leaving nearly nothing in the probes.QuoteThat is what is happening in the video you posted; there is definitively an induced EMF in the oscilloscope probes. They are making exactly the same mistake Lewin made!
Sure. The MIT has always been a nest of incompetent physicists and engineers.
They should hire you, instead!QuoteWatch this video from Trevor Kearney and pay attention to everything what he says. In particular, since you don't seem to understand how is done, look carefully how he derives the equivalent circuit for the RHS of the setup. That is what Lewin should have done.
https://youtu.be/FR8k12j7_Eo (https://youtu.be/FR8k12j7_Eo)
Did you ask Trevor if he thinks Lewin is in error?
Are you afraid of asking?
Because I am pretty sure you are misunderstanding his point of view.
Why should I ask Trevor Kearney a question he has already answer in his videos? You should go and watch his videos and try to understand them! Once you have done that, you'll know for sure who is correct.
Also, do you remember that time you asked me if I had a toroid? Well, I have one now! This beauty just arrived:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1376789;image)
Good. So now you can tell me what are the voltages in the arcs of the ring. I mean from A to R1, from R1 to D, from D to R2, and from R2 to A.
Okay. So, none of you, neither ogden or jesuscf are able to provide an equivalent circuit that reproduces Dr. Lewins experiment, right? And your whole defence to why you cannot do it boils down to "Lewin is an idiot!" :palm:
Can you read? https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647 (https://www.eevblog.com/forum/amphour/562-electroboom!/msg3927647/#msg3927647). Dr.Lewin frustrated himself with overcomplicated experiment, drew wrong conclusions out of measurement results. If you see someone making error - you immediately label him an idiot? Dr.Lewin is brilliant teacher with loads of educating videos, I suggested one for you as well.
I specifically asked jesuscf if he thinks Dr. Lewin is an idiot and he confirmed it.
I don't remember saying that. Can point me where I said it?
EDIT: I see it. You can interpret that in many ways, but I didn't say Lewin is an idiot. I just said 'yes' to your convoluted question. But anyhow, believe what you want, that doesn't change reality. Also, just for the record 'fool' != 'idiot'.
Convoluted, huh? The question was really just what you quoted in your response. I think you understood it quite well. What lead to the question was you quite correctly stating that connecting a measurement instrument to a circuit changes the circuit. So I asked if you thought Lewin was such a "massive fool" that he didn't understand this.
You answering "Yes" means you hold Lewin to be "massive fool who doesn't understand his own experiment". Which is of course completely, entirely different from calling him an idiot.
...
What do you mean with "debunked the MIT guys"? Apparently you have perfectly recreated their experiment. VR1 and VR2 still show different voltages and they are not going to change when you connect your volt meters directly to A and D instead of to the resistor terminals. So, now you have three voltages for VAD, on three different paths. I'd call that a success.
Good. So now you can tell me what are the voltages in the arcs of the ring. I mean from A to R1, from R1 to D, from D to R2, and from R2 to A.
VA_to_R1=16.9mV
VR1_to_D=16.9mV
VD_to_R2=16.9mV
VR2_to_A=16.9mV
The departure from static results is clearly shown by (3), for an electric field intensity resulting from a static charge distribution must lead to zero potential difference about a closed path. In electrostatics, the line integral leads to a potential difference; with time-varying fields, the result is an emf or a voltage.
Meanwhile those who are not yet made their mind, can read detailed article about controversy, Do not miss to watch all the videos linked:
https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work (https://www.electronicdesign.com/technologies/analog/article/21808474/when-kirchhoffs-law-doesnt-work)
I see you are using the "look a squirrel!" fallacy. (Sorry, I forgot the formal name of the fallacy)
I see you are using the "look a squirrel!" fallacy. (Sorry, I forgot the formal name of the fallacy)
Here:
https://en.wikipedia.org/wiki/List_of_fallacies
I'm sure you can pull something out of your nose.
Also, really bad taste in suggesting that Lewin's personal life could mean anything about the physics he discusses.
The only error Lewin committed in his videos are slips of the tongue regarding terminology.
It's really freaking weird too how these types of articles and comments focus so much on Lewin's politeness, tact, 'arrogance,' blah blah blah, or lack thereof, or whatever.
Meanwhile, I've met many of these same kind of engineers who pride themselves on their "blunt tactlessness" and "telling it like it is, man!"
And in the annals of the history of physics and engineering, we have quite a few characters who were pretty famously cantankerous or wryly abrasive but no less absolutely correct - like Heaviside.
Lastly, it's also really weird how much attention is paid to how funny ElectroBoom is and how not-funny Lewin was... despite Lewin developing a reputation as one of the most entertaining physics educators ever to teach at MIT. Clowning in his lectures and telling jokes is trademark of his style. In fact, NONE of this would've even been controversial if he hadn't uttered the phrase 'Kirchhoff is for the birds and Faraday is not.'
I betcha if he had hidden the truth behind the calculus and jargon no one who doesn't understand path-dependent line integrals and non-conservative fields would've even noticed.
I see you are using the "look a squirrel!" fallacy. (Sorry, I forgot the formal name of the fallacy)
Here:
https://en.wikipedia.org/wiki/List_of_fallacies
I'm sure you can pull something out of your nose.
Sure I did:
"Fallacy of quoting out of context (contextotomy, contextomy; quotation mining) – selective excerpting of words from their original context to distort the intended meaning."
Thanks.
Also, really bad taste in suggesting that Lewin's personal life could mean anything about the physics he discusses.
The only error Lewin committed in his videos are slips of the tongue regarding terminology.
It's really freaking weird too how these types of articles and comments focus so much on Lewin's politeness, tact, 'arrogance,' blah blah blah, or lack thereof, or whatever.
Meanwhile, I've met many of these same kind of engineers who pride themselves on their "blunt tactlessness" and "telling it like it is, man!"
And in the annals of the history of physics and engineering, we have quite a few characters who were pretty famously cantankerous or wryly abrasive but no less absolutely correct - like Heaviside.
Lastly, it's also really weird how much attention is paid to how funny ElectroBoom is and how not-funny Lewin was... despite Lewin developing a reputation as one of the most entertaining physics educators ever to teach at MIT. Clowning in his lectures and telling jokes is trademark of his style. In fact, NONE of this would've even been controversial if he hadn't uttered the phrase 'Kirchhoff is for the birds and Faraday is not.'
I betcha if he had hidden the truth behind the calculus and jargon no one who doesn't understand path-dependent line integrals and non-conservative fields would've even noticed.
The article also gives too much importance to popularity, which is not a very good parameter to ascertain the techical credibility of an engineer or a scientist.
(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT3aTabQrRyChwC7v17fgANsdck0V3X6czw0g&usqp=CAU)
As for politeness, I like one quote (https://lkml.org/lkml/2012/7/6/495) from Linus Torvalds who once suggested that stupid people should be "retroactively aborted" as they wouldn't be likely able to survive babyhood due to their inability "to find a tit to suck on".
He justified his behavior by saying that he saw political correctness destroy multiple projects out there and he didn't want that for Linux kernel.
I've been in the industry long enough to understand what he's talking about.
But since KVLiars love stupidity, and they fail every time, like KVL in a circuit under a varying magnetic field, I tend to belive that they are also incapable of satisfying even their most basic instincts.
Perhaps one redeeming point of the article is that the author admits in the end that KL fail sometimes, contradicting Mehdi, who stupidly asserts that "Kirchhoff always holds".
I see you don't know how mesh analysis work either.
Reading books is what you should do, instead..
Start from Hayt, chapter 9 and try to understand why the author's differentiate between potential difference and voltage.
The books in your picture look alarmingly unread.
Reading books is what you should do, instead..
Start from Hayt, chapter 9 and try to understand why the author's differentiate between potential difference and voltage.
The books in your picture look alarmingly unread.
Engineer: "That model does not look right"
Scientist: "Eureka!"
When engineer say "you have to place wire here to get voltage X but have to place wire there to get voltage Y"- he gets fired.
When scientist say exactly same words - he gets worshipped.
Go figure.
Reading books is what you should do, instead..
Start from Hayt, chapter 9 and try to understand why the author's differentiate between potential difference and voltage.
The books in your picture look alarmingly unread.
Do you expect them to read books and on top of that understand what they read? You're asking too much. KVLism is based on ignorance. The more you're ignorant, the better. Because then they can claim with even more propriety that they have "debunked" some reputable scientist, engineer or scholar.
When they resort to books, it is only to select the passages that, out of context, appear to support their false claims, and rig their experiments until they get the results they think will prove them "right".
The books they show are only to impress the casual reader of the thread, or to serve as an amulet to ward off the evil people that show their favorite ignorant blogger is fundamentally wrong.
Reading books is what you should do, instead..
Start from Hayt, chapter 9 and try to understand why the author's differentiate between potential difference and voltage.
Got it: Magnetic potential difference units are amperes. Electric potential difference units are volts.
Maxwell's book is new. As for Hayt's book:
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1377895;image)
Did you have to buy four edition because your books consistently miss pages?
I see you don't know how mesh analysis work either. Lewin has a video on that, well, actually more like 5 videos on that. So go watch them then come back to what you said above and see if you can find where you are wrong.
You see, all of that we concluded by simple observation. Now, we can try to predict an outcome with what we learned. If you repeat the same experiment and now place a voltmeter like the picture below (in red), we can expect pretty much that the voltage we will measure will either be zero or much lower that the voltages we previously measured. Why? Because we will have a blue guy there, who will not be able to embrace a varying magnetic field.
(https://www.eevblog.com/forum/amphour/562-electroboom!/?action=dlattach;attach=1378060;image)
Engineer: "That model does not look right"
Scientist: "Eureka!"
When engineer say "you have to place wire here to get voltage X but have to place wire there to get voltage Y"- he gets fired.
When scientist say exactly same words - he gets worshipped.
Go figure.
If you place the multimeter as you show in the image, what you get is the voltage drop in the resistance of the wire which is very small.
The induced EMF in the ring wire is cancelled by the induced EMF in the voltmeter probes.
Also, do you remember that time you asked me if I had a toroid? Well, I have one now!
VA_to_R1=16.9mV
VR1_to_D=16.9mV
VD_to_R2=16.9mV
VR2_to_A=16.9mV
Also, do you remember that time you asked me if I had a toroid? Well, I have one now!
The induced field generated by a toroidal core is not circularly symmetric around the section of the core. It's more like the magnetic field generated by a single loop of current:
(https://i.stack.imgur.com/rsmwJ.jpg)
The induced field is stronger inside, being maximum on the axis of the toroid, where all 'cross sections' of the core contribute constructively and decreases faster than 1/r at the exterior. Therefore, your circular ring - even if it is perfectly circular and perfectly concentring to a perfectly circular cross-section core - will not experience the same Eind field in all points of its circumference.
The infinite long solenoid, with its perfectly circular Eind field lines, on the other hand, allows you to pull the trick of considering the contribute on arcs of equal length to be the same. But a toroidal core? No.
Therefore your answer about havingQuoteVA_to_R1=16.9mV
VR1_to_D=16.9mV
VD_to_R2=16.9mV
VR2_to_A=16.9mV
in the approximately circular ring around your square section core is... you guessed from the preview... WRONG.
And this is where I wanted to take you - and Jesse - some ten-fifteen pages ago when I asked you to specifiy your 'McDonald voltages' for all parts of that 'killer question' circuit that Jesse kept reposting. But you guys ran away like politicians from a truth serum.
Like you seemingly did when I asked you to explain why Hayt - which defines voltage as the path integral of the electric field - makes a difference between potential difference (to be used in the static case) and voltage/emf (to be used in the dynamic case).
In case anybody is wondering about drilling ferrite cores, keep in mind that they are really hard to drill (that's is, it took me ~1 h to drill 6.5 mm |O )
Also, do you remember that time you asked me if I had a toroid? Well, I have one now!
The induced field generated by a toroidal core is not circularly symmetric around the section of the core. It's more like the magnetic field generated by a single loop of current:
(https://i.stack.imgur.com/rsmwJ.jpg)
The induced field is stronger inside, being maximum on the axis of the toroid, where all 'cross sections' of the core contribute constructively and decreases faster than 1/r at the exterior. Therefore, your circular ring - even if it is perfectly circular and perfectly concentring to a perfectly circular cross-section core - will not experience the same Eind field in all points of its circumference.
The infinite long solenoid, with its perfectly circular Eind field lines, on the other hand, allows you to pull the trick of considering the contribute on arcs of equal length to be the same. But a toroidal core? No.
Therefore your answer about havingQuoteVA_to_R1=16.9mV
VR1_to_D=16.9mV
VD_to_R2=16.9mV
VR2_to_A=16.9mV
in the approximately circular ring around your square section core is... you guessed from the preview... WRONG.
And this is where I wanted to take you - and Jesse - some ten-fifteen pages ago when I asked you to specifiy your 'McDonald voltages' for all parts of that 'killer question' circuit that Jesse kept reposting. But you guys ran away like politicians from a truth serum.
Like you seemingly did when I asked you to explain why Hayt - which defines voltage as the path integral of the electric field - makes a difference between potential difference (to be used in the static case) and voltage/emf (to be used in the dynamic case).
You seem to agree that in my setup VA_to_R1=VR2_to_A and VR1_to_D=VD_to_R2. Is that correct?
In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
Engineer just measured 12VAC on transformer output. Wannabe scientist: as resistance of transformer secondary winding is zero, then voltage on terminals of transformer secondary is I*R meaning - zero. [edit] Those guys claim to know Faraday's law? C'mon.
In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
Engineer just measured 12VAC on transformer output. Wannabe scientist: as resistance of transformer secondary winding is zero, then voltage on terminals of transformer secondary is I*R meaning - zero. [edit] Those guys claim to know Faraday's law? C'mon.
This is also the Engineer who's designs pass EMC testing.
In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
I see. I have nothing to discuss with you then.
Dumb Engineer doesn't want to care about what's happening inside the transformer. He just measures across the transformer terminals and is happy. Engineer who knows Faradays Law understands why his measurements are sometimes giving unintuitive results. This is also the Engineer who's designs pass EMC testing.