#562 – Electroboom!

[Jesse Gordon]

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.

Because it will uselessly waste space here.

Besides, 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.

Well your crystal ball failed you this time.

Thinkfat solved it correctly and with elegance.  Evidently he read the notes in the challenge and understood them and he came up with the same result as I did which also agrees 3 digits past the decimal with an online circuit simulator I tried (which only shows 3 digits past the decimal).

What exactly more needed to be modeled?

[Jesse Gordon]

Also, Hey, did you see my request to you here? 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.

Alright, the jury is in! bsfeechannel and Sredni couldn't solve it.

You solved it absolutely correctly, and much more elegantly than I did.

You know this stuff better than them, they should be listening to you, not you listening to them.

I solved it this way:

primary_voltage=100
resistor_ohms=0.2
primary_turns=100
secondary_turns=10
resistance_per_foot=0.001
feet_per_turn=1

primary_resistance=resistance_per_foot*feet_per_turn*primary_turns
secondary_resistance=resistance_per_foot*feet_per_turn*secondary_turns

resistor_volts=(primary_voltage*resistor_ohms)/(resistor_ohms*(primary_turns/secondary_turns)+secondary_resistance*(primary_turns/secondary_turns)+primary_resistance*(secondary_turns/primary_turns))

The circuitlab.com online simulator said 9.479v (I don't have an account there but they let you use it free for like 12 moves or something then they demand money.)

My answer is 9.4786729858
and your answer (10/.211)*.2=9.4786729858 as well.
(Rounded to 10 digits past the decimal in both cases.)

I now know that you actually do know more about transformers than I do!

Thank you!

[Jesse Gordon]

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.

Try holding that crystal ball up to your computer screen, see if it works like a magnifying glass, because you obviously hadn't read what I wrote in my challenge 

The 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.

It was NOT a hard problem to solve for someone who knows even a tiny bit more about transformers than I do.

I picked that level of complexity because it was right at my limit, 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.

As it turns out, the one who has been more sincere and more willing to try and be helpful is the one who solved it. Interesting.

Speaking of crystal balls, I got a couple of those 200mm K9 glass balls for various science experiments, and they do make nice magnifying glasses. Works for woodburning too.

[Sredni]

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

The 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.

I told ya.
Defending any simplification he made, no matter how unrealistic that may be.
The famous 'real world' where cores have infinite permeability, there is no hysteresis, no saturation, ideal coupling and the generators are perfect generators with no internal resistance whatsoever and infinite compliance that can drive even an inductance made of one turn without being loaded by the near zero reactance.

It's a strange 'real world' that in which you live in.
Now I am really wondering if you ever modeled a real transformer. But never mind. Can we consider this parentheses closed?
Do you feel better now? Has this helped you resetting to default so that you can bring up the same objections over and over again?

Because I tell you what: what I write, and the drawings I am making, I am not doing that for you. I know you are a lost cause.

Can we get back to Lewin's ring now, and to the simple one turn transformer you have yet to understand the working of?

Edit: clause ->cause

[Jesse Gordon]

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).

Below: Starting at the top volt meter, going clockwise: 0v, -1/3v, -0v, 1/3v.

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.




And also, nobody has directly answered the following for me yet, do you mind clarifying? Thank you!



Above: Will V1 and V2 read the same?

[Jesse Gordon]

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?

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.

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?

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"?

Look, I'm sure you'd make a great Hollywood scriptwriter. In fact, your sketches are so good you could make great storyboards too.

Your little stories are a lot of fun to read, but the problem is they are rather ambiguous to someone with my skill level. I'd think maybe I was just really dumb, but then when I try to get clarification with simple unambiguous questions, I get more drama, not answers.

Perhaps I misunderstood some of what you said in your nice long post with lots of pictures. But I'm doing the best I can. If you can spin all these great yarns and write and conduct a 3 page forum film, why not just answer the simple questions, like this:

 

Will V1 and V2 read the same? (Neglecting of course any non-uniformity of the core and neglecting also the added capacitance of the twisted pair.....)

[Sredni]

Sigh...

YES. V1 and V2 will be the same.

[thinkfat]

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.

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?

[Jesse Gordon]

Sigh...

YES. V1 and V2 will be the same.

So the V1 configuration and the V2 configuration are functionally identical, and yet  V2 is lumpable and V1 is not?

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?

Does KVL fail because the volt meter readings around the path would no longer sum to zero? or because of a technicality of the definition of voltage that changes when those two wires aren't twisted together (or at least run very close to eachother)?

Thank you!

[Jesse Gordon]

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.

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?

Thank you for checking, but no, I understood that 2R is a resistor with twice the resistance of R.

As long as you are OK with how I've drawn the toroid core as a cut-away strictly for clarity (but assume it's a full toroid)  and the physical locations and polarities of my 4 volt meters and the physical path of their leads and the physical location of the two resistors,  then I see no reason to change my analysis.

I honestly believe that if I were to set up an actual test and measure with a real volt meter as shown in my diagram above, I would get the indicated readings. (Of course the sign indicates phase, not actual DC voltage offset.)

EDIT PS: I'm super curious about what your prediction is...! Any chance you might tell me? I put my prediction on the line.. /edit

Thank you!

Sednri says that both V1 and V2 would read the same, in the following diagram, do you agree?:

[Sredni]

Sigh...
YES. V1 and V2 will be the same.

So the V1 configuration and the V2 configuration are functionally identical, and yet  V2 is lumpable and V1 is not?

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!

[Jesse Gordon]

Sigh...
YES. V1 and V2 will be the same.

So the V1 configuration and the V2 configuration are functionally identical, and yet  V2 is lumpable and V1 is not?

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!

Why are you so reluctant to answer my questions? That's how I learn best -- understand how reality is, then learn why. You're trying to tell me why without even showing that we're talking about the same reality.

I saw your very nice diagram that showed dots on the loop which did not contain within its area dB/dt (lumped) and I saw how you had dots all through the whole loop when the wires did not come near eachother between the transformer and volt meter (unlumpable).

So consider my entire V1 path to have dots if that's what you're asking.

And now you say that the voltage can be non-unique. What do you mean? Do you mean that for configuration V1, my volt meter can read different voltages depending on something?
Or do you mean that the voltage is non-unique in that it's also the same voltage measured in V2? non-unique means there could be another one like it.
But another what? Another location/configuration? Or another voltage?

Are you talking about measured voltages being non-unique? or calculated voltages?

Every time I ask questions, none of them are asked and more nebulous statements are given which only raise more questions.

Can we just agree that in my V1 and V2 case, FOR THE CASE OF ACTUALLY MEASURING WITH A VOLT METER, KVL will appear to hold, in that the measured values will all sum to zero?

Or are you saying that using V1 in a loop would NOT sum to zero as measured with a volt meter?

Then you can go on to explain why, by some definition or technicality, KVL isn't actually holding, even though my experiments with a volt meter make it look like it's holding.

Thank you.

[jesuscf]

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?

What you wrote there is not describing Lewin's experiment at all!

[Sredni]

never mind.
here's the picture.


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?

[Jesse Gordon]

never mind.
here's the picture.


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?

Sorry, I had no idea you couldn't see postimg inlines. This is the "V1, V2" diagram I've been referencing, I thought you could see it: https://i.postimg.cc/fTgyDNp0/20211119-030105.jpg
If I ever say "In the diagram below" and you don't see a diagram, please let me know!!!!

Of course I know that if an unambiguous voltage reading cannot be obtained across the terminals of an element due to either the element or the instrument it  will make not only KVL fail but all analyses of all types which would depend on an unambiguous reading. Like I've been saying all along, if you're measuring two unknowns, you're measuring neither of them.


So I look at your diagram, are we still talking about a toroid?

It looks like you're showing the wire passing through the physical volume of the cross section of the core, as if there were holes drilled in the core..... Or did we leave off talking about toroid transformers and I didn't notice? If so, what are we looking at here? an air core transformer?

OF COURSE if you drill holes in your toroid cross section and run your wire through those drilled holes you will get various fractions of a turn of voltage differences.
(That's why I was joking about drilling a hole in a toroid to get a half-turn as a joke a week ago.)

It's the same if you added or removed turns from your secondary between measuring it's voltage and measuring voltage across other components in the loop.

Please explain, are we still talking about a toroid?

If we are talking about a toroid, then are you saying that the only ambiguity is if the volt meter leads have some magical property which allows them to occupy the exact same physical space as the core material?

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 with the outputs of toroid transformers in both the V1 and V2 configurations in my diagram? https://i.postimg.cc/fTgyDNp0/20211119-030105.jpg



Can we agree that in my diagram above, both V1 and V2 configurations using REAL PHYSICAL TOROIDS AND WIRES, and real volt meters, KVL would give every appearance of holding in real life?

Once we agree on observable reality then we can talk about what and why behind it. But talking about what and why is meaningless if we aren't even talking about the same observable points of evidence.

Thank you.

EDIT: PS: If you're saying that my volt meter reading can change due to the changing of the path of the wires OUTSIDE THE CORE(I can't believe I have to say that..), then I need to know that so I can test it out and see for myself. Thanks!

[Sredni]

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.

[bsfeechannel]

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.

[Jesse Gordon]

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.

I don't know what you mean when you say "THIS system." Your computer? Your internet system? The EEVBlog system? Your Screen reader? Do you have one of those qwerty monitors? 

It is fascinating to see the amount of irrational objection you need to throw to persist in your religious blindness.

Actually you're describing yourself. Do you know how many times I've specifically clearly asked you whether configuration V1 and V2 would cause KVL to appear to hold when measured with a volt meter as described in the following diagram? https://i.postimg.cc/fTgyDNp0/20211119-030105.jpg

You bob and weave and rant, but you will not answer that question. It's like trying to get a pious priest to cut lose a string of profanities from the podium.
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.

I even keep giving you the "out" of saying that KVL is only appearing to hold in this situation. You can just say "Yes it appears to hold, but...." then we can talk about the but.

Look at your leadin:

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?

From that I would say that you do know that KVL would give every appearance of holding, but you can't bring yourself to say it, so you're preparing to argue that even though KVL appears to be holding, it's not actually holding because the meters aren't measuring what I think they are measuring.

Since you asked, I have 5  AC/DC amp clamps ranging from a 2 amp to a 2000 amp unit. I've also worked with hall effect sensors in various projects over the years.
I also have 4 CRT type analog oscilloscopes, and I think the 3 Tektronix ones of them work. The 4th is an old heathkit that was all tube based, it doesn't work. All of them are statically deflected, which is interesting because that actually does measure voltage without an electrical current flowing across the measuring element - the beam of electrons is steered due to the current-less electric field.
Also 2 junky Siglent 2GGS/s DSO scopes, a 2 chan and a 4 chan.

I once offered to send one of the old Tek units for free to a guy in Germany if he paid shipping, he was happy till he found out how much it cost to ship a 50lb large chunk of vintage metal equipment LOL.

Why won't you just admit that KVL will appear to hold in my V1 and V2 configurations in the above linked diagram if measured with actual volt meters, then we can move on to why it's not?
If you haven't the ability to solve a simple ideal transformer step down problem, and you haven't the honesty to admit that KVL will appear to work in a case where you know it will appear to work, then how can I trust you to tell me anything else straight?

Thing is, I can hook up some toroid transformers, make a loop, and measure around the loop, and KVL will appear to hold. So can you. Why not admit it?

Once I see that you have the integrity to admit to observable reality, then you can start telling me what's going on behind that observable reality.

But so far, your entire performance looks to me wild savage religious dance to try and save your Lewin.

As for me, it's not religious. It's just me sayin' Hey, I got volt meters and transformers, I made a loop and measured around the loop and summed the voltages, and it all summed to zero.

You think you can show me that KVL actually fails int he real world with toroidal transformer secondaries? Then for pete's sake DO IT! Otherwise, stop telling me it fails in that situation.

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.

I'm not exactly sure what topology you have in mind for me to try. I could take some guesses, but wouldn't you know it, KVL would appear to work and you'd say I did it wrong.

So let's do it this way.

I have two nice EI-Core transformers with 200mv/turn, or 100mv/half-turn. If  you want me to use a toroid, I can just use half of them.

Or if I have to use a toroid I can get one off ebay.

Please draw me the circuit topology that you want me to test, the one that you think will fail KVL.

Thank you.

[jesuscf]

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 are more than one way of generating an emf and using it in a circuit?

[Sredni]

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?

[Sredni]

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 Eind that causes charges to move (edit: I am talking about the surface and interface charge that follows the gradients in permeability and conductivity). 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 and, together with the conservative field Ecoul of the displaced charge, result in the field inside the material that follows Ohm's law (in its local form).
And since electrons 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.

[Jesse Gordon]

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.

I can't help but chuckle at the contradiction you present.

On one hand, you're telling me we don't need no gurus because nature tells us.

Then you end off talking about what the first thing you learned in electromagnetism courses.

So which is it? Nature? Or the gurus that write the books and teach the courses?

All I'm asking is if you think there is a loop topology involving the output windings of regular closed-magnetic-circuit transformers as elements in a multi-element loop which cause KVL to fail, I want to know about it because I want to build such a loop and see KVL fail it with my own eyes.

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.

And supposing the conductor is in a changing magnetic field? Why are you bringing up static fields when we're talking about AC transformers?
The fact that static electric fields cannot cause a sustained voltage along a superconductor simply does not mean that a dynamic magnetic field cannot cause a dynamic voltage difference per Faradays Law across the ends of the conductor.

As best as I can tell, both Dr. Belcher and Dr. McDonald disagree with you.

Belcher seems to quote Feynman and claim that the -∫E.dl=0 for a superconductor, but says that the full equation for the loop includes -L(dI/dt) which has nothing to do with the -∫E.dl term, and that -L(dI/dt) is NOT always zero in a changing magnetic field, and so therefore a wire in a changing magnetic field (even a super conductor) can in fact have voltage across it for completely non-ohmic reasons.

Like I said, what I want is what nobody has been able to provide for me yet. That is a loop of elements consisting of resistors and one or more transformer winding which cause KVL to fail visible when I test around the loop with a volt meter following the rules for KVL.

So far? Nada.

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.

That's worth commenting on again. An entire thread about AC transformers, and you bring up static electric fields. Really?

You very well know that your argument is absolutely useless when it comes to dynamic magnetic fields otherwise  transformers  wouldn't put out voltage.

This is totally amazing. You really don't know this stuff, do you? Why on earth would you bring up static fields? Did you not know? Or did you think I wouldn't know the difference?
What, is this a poker match? Why not just be honest, give your best evidence, and let the cards fall where they may?

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 

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

And where is this nature when I turn on my volt meter? Why will nobody give me an example of KVL failing due to the secondary winding of a normal closed-magnetic-circuit transformer being part of the loop?

The conclusions of your experiment are wrong because you don't listen to what the phenomenon right in front of you is telling.

Thank you Dr. bsfeechannel!

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. And you know if I solved it (even if it took me hours) it can't be too hard, right?

In all seriousness though, why not show me a topology of resistors and toroidal transformer secondaries in a loop where KVL will fail as measured by my volt meter?

[Jesse Gordon]

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.

Are you arguing that the only reason KVL doesn't hold for a loop with a transformer secondary as an element is because Kirchhoff didn't mention?

In other words, yes, KVL appears to hold for loops with transformer secondaries in it, but since Kirchhoff didn't specifically mention that at the time, then it's not technically  holding?

A big definition word game?

[Jesse Gordon]

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?

For exceptionally small versions of five and exceptionally large versions of zero, possibly 

And the way you refuse to provide a diagram for me to try which will cause KVL to fail, I think maybe for you 5 might equal 0.


Look my friend, I really appreciate your effort. I really do.

But your inability to grasp the basic concepts plus your refusal to answer questions which you think will undermine your house of cards makes your argument extremely weak and unconvincing.

But carry on, it is your argument to make, weak as it may be.

If you ever figure out how nature can speak to me through my volt meter, please do tell me. Until then, it looks to me like KVL holds up just fine even when some of the elements are transformer secondaries.

[Sredni]

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?