EEVblog > The AmpHour Radio Show
#562 – Electroboom!
thinkfat:
--- Quote from: Jesse Gordon on November 25, 2021, 06:26:26 am ---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
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."
--- End quote ---
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.
thinkfat:
--- Quote from: Jesse Gordon on November 24, 2021, 09:59:18 pm ---
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.
--- End quote ---
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?
--- Quote from: Jesse Gordon on November 24, 2021, 09:59:18 pm ---
--- Quote ---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.
--- End quote ---
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.
--- End quote ---
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? So the only voltage source must be the red wire, right? So which way will you have it? It cannot be both.
--- Quote ---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.
--- End quote ---
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.
Jesse Gordon:
--- Quote from: thinkfat on November 26, 2021, 08:05:05 am ---
--- Quote from: Jesse Gordon on November 26, 2021, 06:53:29 am ---[...]
--- End quote ---
Sorry man, it's all been explained and shown in pictures and equations. But you just ignore them.
--- End quote ---
And you're ignoring observable reality, and refusing to answer questions which would allow you to see how wrong you are, so what good are your so called "explanations?"
You used to be willing to put your beliefs about reality to the test. Now you're getting like the other more experienced lewinites who like to wax eloquent but refuse to actually answer questions because they know they'll fail reality checks.
--- Quote ---Instead you make up incomplete analogies, like the "wall inside the transformer".
--- End quote ---
Snedri came up with the virtual wall analogy. He had his outside the transformer as an infinite plane, but putting it inside like I did has the exact same effect on measurable reality.
--- Quote ---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.
--- End quote ---
The thing is, I do understand how transformers model and measure. You don't. That's why you've made like 5 wrong predictions now, because you just don't understand observable reality when it comes to transformers. But hang in here, if you don't slip off into never-never land like the others, you'll get to where you understand it.
--- Quote ---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.
--- End quote ---
That sounds like an argument from personal conviction, no? That's incredibly weak.
You say "The electric field is there, extending to infinity." But you haven't told me how I can measure it.
Nor have you said whether it is blocked by Faraday shielding, or earth or water or whether there is any way to detect it.
How can I measure this electric field extending to infinity as you first described it?
Speaking of making things up... I think you made that one up.
You also keep refusing to answer whether the electric field from the following transformer also extends into infinity:
Seriously though, how can I measure this electric field extending into infinity from a toroidal transformer?
I can see if you had an infinitely long solenoid, then you could argue that you had both magnetic and electric fields extending to infinity since the solenoid itself extends to infinity.
But the beauty of a toroid is that it wraps up infinity to the area the size of a wallnut, or however big the toroid is.
As I said, seriously, what's the deal with this electric field around a toroid that extends to infinity? An unmeasurable unstoppable field?
You made it up, and that's like the 5th major misunderstanding you've demonstrated.
Jesse Gordon:
--- Quote from: thinkfat on November 26, 2021, 08:34:15 am ---
--- Quote from: Jesse Gordon on November 25, 2021, 06:26:26 am ---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
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."
--- End quote ---
This "wall inside the transformer" is not equivalent.
--- End quote ---
Please explain. Do you mean that assuming no probe wires breach the wall in the above diagram, there is still path dependence effecting the probes wires?
Are you saying somehow my volt meter can possibly read anything other than the unambiguous voltage of 1 turns worth of induced voltage, assuming my volt meter leads don't breach the wall?
--- Quote ---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.
--- End quote ---
Whaddya mean? Each of my half turns were exactly a half turn. And all four voltages summed to zero.
Your pipe dream about this magic E-Field that extends to infinity has got you all confused. Please find a way to measure that or give up the idea.
Jesse Gordon:
--- Quote from: thinkfat on November 26, 2021, 12:27:30 pm ---
--- Quote from: Jesse Gordon on November 24, 2021, 09:59:18 pm ---
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.
--- End quote ---
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.
--- End quote ---
As I said before, that's why we MODEL and MEASURE a toroidal transformer in an integer number of turns.
If we have an EI core, then we can use half-turns.
--- Quote ---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?
--- End quote ---
So far as you continue to shield yourself from reality, it's not going to make sense. I have asked you multiple times and I ask again: In the diagram directly below, will V1 and V2 read the same voltage? Will either V1 and/or V2 be suitable for use as an element in a KVL loop?
If you were to answer that truthfully, you'd have to say that yes they both read the same and yes a KVL loop would measure to be holding with either V1 or V2. (Heh, or both, as two different elements, which is what my EI-Core was.)
At the end of the day, how can you not see that KVL gives every appearance of holding in this case?
--- Quote ---
--- Quote from: Jesse Gordon on November 24, 2021, 09:59:18 pm ---
--- Quote ---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.
--- End quote ---
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.
--- End quote ---
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?
--- End quote ---
Wrong.
I know this is hard for you to understand, but bear with me.
It is completely possible for the induced voltage to be induced all the way around while modeling it for the sake of KVL as a lumped voltage source BECAUSE none of the rest of the mesh passes through the core, and thus none of the rest of the mesh resides in any non-conservative field, because all paths that do not cross through the core are path-independent.
--- Quote ---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?
--- End quote ---
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.
--- Quote ---So the only voltage source must be the red wire, right? So which way will you have it? It cannot be both.
--- End quote ---
How can you not see that I'm talking about HOW IT MODELS AND MEASURES?
KVL works on how it models and measures.
--- Quote ---
--- Quote ---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.
--- End quote ---
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
--- End quote ---
ha ha very good! :-DD
But in all seriousness, I have clearly demonstrated that when we run our volt meter leads along planes where there are no fields, we can in fact measure induced voltages on even many topologies of air-core and open ended transformers.
--- Quote ---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.
--- End quote ---
So can we just add up the ohmic losses, calculate the induced voltage, and sum that all up and find it to be zero, and then deduce that KVL holds, even for Lewin's loop?
After all, if he had summed up his ohmic losses he could have then flipped the sign and calculated the induced voltage, and if he had them added that all up, it would have summed to exactly zero! ha ha ha :-DD :-DD :-DD :-DD
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