Is MIT Prof. Lewin wrong about Kirchhoff's law?

[yungman]

How about some auto highZ ignition leads?

But that would be uniform resistance. YOu need to have something of two different resistance per unit length and combine together.

I think we might be onto something here, it would be very interesting to see the result. I bet if you marry half a turn of of 900 ohm total and half a turn of 100ohm total to form a loop, you would not get even close to 9:1 voltage ratio because if I am right about the micro sources, you will be measuring the resistor and the source instead of just the V=IR. Note that even if you don't get the V+IR relation, don't be too quick to say Ohm's law don't work under non conservative field etc. Because if you model the micro source in, KVL still work. Well talk is cheap, one experiment speak louder than anything else.

Maybe if you use one kind of resistor wire, half a turn make up of single wire and the other half turn make up of 9 wires in parallel, twist 9 wires together, use a meter to measure the length of the exact value of resistance you want (900ohm), then just cut the right length.

 

[yungman]

I'm open to donations :)

I thought about the carbon track, but I have no way of making it very regular. I was thinking of just writing with a graphite pencil on some transfer paper, but don't think that would come out very well.

Even if you build the loop with the discrete resistors like what I drawn, you should see reasonable results. If you make sure the wire junction between the two resistor is as short as possible(open twisted end is not part of the loop and don't matter like in my drawing), over 80% of the length of the loop will be of resistor material. You will see the effect if any. Don't sweat too much if you cannot find the resistent wires or carbon deposit. I have a suspicion that you are not going to get anywhere close to 0.9V on the 900 ohm resister if my theory of distributed source is correct, might not be even 0.5V. If you get close to 9:1 ratio, then I am blowing hot air. But in that case, still KVL holds and the voltage is not path dependent either.

We are looking forward to your result. Result speak louder than anything.

 

[yungman]

Guys, while we are waiting for the result, I have time just thinking about some theory that was thrown around in this case here:

Why are we talking about Lorentz force? My understanding about force only act on a charge that is moving. In this case, after the battery was removed, nothing is moving the electrons around the loop, only some thermal motion. Lorentz don't even apply here. It is very clear that

\vec F = q(\vec u X \vec B)\; \hbox { where } \;\vec u \;\hbox { is the velocity. }

And there is no force asseted on the charge if the charge is not moving. Recall magnetic field move the wire ONLY when there is a current passing through the wire? Also one more important point, the book very specificly said that the static magnetic field do not change the velocity of the particle, it only change the direction of the particle. So if the only motion of the electrons in the wire and resistors only change from random motion to random motion plus a few degree shift...still random, no current. Refer to P207 of Griffiths.


In my opinion, the formula in play in our case is :

V = \int _S (\nabla X \vec E) \;\cdot\; \hat n \; dS \;=\; \int _C \vec E \;\cdot\; \hat T \;dl \;=\; \int_S \frac{\partial \vec B}{\partial t} \;\cdot\; \hat n \;dS

From the experiment, the good professor use a changing magnetic field to induce the voltage into the loop. This is a time varying magnetic field and Lens law is in action in this case. And this is the voltage that drive the resistors. We'll have to see my distributed micro voltage inside resistors theory pan out or not.

 

[yungman]

Hey where is the enthusiasm?

 

[yungman]

Dr. Lewin is among the world's most qualified instructors regarding this material. I'm a little surprised at the EEs (or non-EEs) in the industrial community who are bashing Dr. Lewin. Those who do make me wonder how much e/m field theory they've had. Nothing personal, but will the critics of Dr. Lewin please state explicitly the errors in Dr. Lewin's teachings? He's a prof at MIT, an institution world renowed. Who are these critics anyway? What are their credentials? I'm just wondering.

One reason, first thing come to mind as I watch the first video is "How the hack he did the measurement"? How theoretical people that never held a probe will said you measure from the same two point and get two different reading. What? By hooking the scope probe from the left side or the right side to the same two points?

One of the difference between a physicist and engineer is the engineer has to produce something tangible, measuring at a real point, not an imaginary point like the professor did. I question the knowledge of electronics the professor has, and how many hours he spent on designing and building circuits. You understand this experiment is electronics?

In his experiment, I bet he connected the two resistor by wires, and that he missed the moon. I am waiting for Sarumonkee to come back with the result of the multiple resistors. But as I posted, I disagree that Lorentz force are in play in this case. It is FL that is in play.

Yes I notice the EM in EE is different from physics. We study a lot deeper into phasor, transmission line theory, smith charts etc. where physics (electro dynamics) get deeper into materials, potentials and more math. I follow the advanced EM courses of U of Santa Clara and pretty much finished what they taught. I did not attend any school, hack, I study mostly on my own in my whole career. I this is my third round studying EM, this time I study a lot of materials in “Intro to Electro Dynamics “ by Griffiths. There is a lot of stuffs that the EE books do not cover. BUT what we are arguing here is very basic laws like FL, KVL and conservatives. This are covered in the first 2 chapters. I still believe the professor did the experiment wrong. Nothing to do with the theory.

 

[cabraham]

Guys, while we are waiting for the result, I have time just thinking about some theory that was thrown around in this case here:

Why are we talking about Lorentz force? My understanding about force only act on a charge that is moving. In this case, after the battery was removed, nothing is moving the electrons around the loop, only some thermal motion. Lorentz don't even apply here. It is very clear that

\vec F = q(\vec u X \vec B)\; \hbox { where } \;\vec u \;\hbox { is the velocity. }And there is no force asseted on the charge if the charge is not moving. Recall magnetic field move the wire ONLY when there is a current passing through the wire? Also one more important point, the book very specificly said that the static magnetic field do not change the velocity of the particle, it only change the direction of the particle. So if the only motion of the electrons in the wire and resistors only change from random motion to random motion plus a few degree shift...still random, no current. Refer to P207 of Griffiths.


In my opinion, the formula in play in our case is :

V = \int _S (\nabla X \vec E) \;\cdot\; \hat n \; dS \;=\; \int _C \vec E \;\cdot\; \hat T \;dl \;=\; \int_S \frac{\partial \vec B}{\partial t} \;\cdot\; \hat n \;dS

From the experiment, the good professor use a changing magnetic field to induce the voltage into the loop. This is a time varying magnetic field and Lens law is in action in this case. And this is the voltage that drive the resistors. We'll have to see my distributed micro voltage inside resistors theory pan out or not.

The Lorentz eqn has 2 terms, 1 for electric, & 1 for magnetic. I've already stated said eqn as F = q(E + u X B).

Regarding the mag field influence on a charge, it can indeed change its direction, but not its speed or kinetic energy. By changing its direction, its "velocity" is also changing, as velocity is a vector quantity consisting of speed & direction.

I use momentum & kinetic energy when describing Lorentz force. An E field can change both, but a B field can only change momentum, not KE.

Did I help, or make matters worse?

Claude

 

[atyy]

Lewin is not a theorist.

 

[yungman]

The Lorentz eqn has 2 terms, 1 for electric, & 1 for magnetic. I've already stated said eqn as F = q(E + u X B).

Regarding the mag field influence on a charge, it can indeed change its direction, but not its speed or kinetic energy. By changing its direction, its "velocity" is also changing, as velocity is a vector quantity consisting of speed & direction.

I use momentum & kinetic energy when describing Lorentz force. An E field can change both, but a B field can only change momentum, not KE.

Did I help, or make matters worse?

Claude

No, since the only motion of electrons in the circuits with no current is random motion, changing the direction of a random motion is still random motion. You cannot make the random motion to become the direction of the wire to travel down the wire as current.

It is very obvious that FL is in play like what I wrote. The resistor body is still part of the loops. As I said before, if the professor use a 6" wire to connect the two resistor, most of the induced emf is on the wires. In case of the loop making up of resistors material, the result is the same where the micro voltage sources are embedded inside the resistors. Still waiting for the experiment result that if what I postulated is true, we are not going to see 9:1 voltage ratio on those resistors, not even close.

 

[yungman]

Lewin is not a theorist.

I can asure you he is not hands on!

 

[yungman]

The Lorentz eqn has 2 terms, 1 for electric, & 1 for magnetic. I've already stated said eqn as F = q(E + u X B).

Regarding the mag field influence on a charge, it can indeed change its direction, but not its speed or kinetic energy. By changing its direction, its "velocity" is also changing, as velocity is a vector quantity consisting of speed & direction.
BUt as I said, if there is no current in the loop, electrons are moving randomly. So applying a mag field just change the direction of the random movement and still is random. Not current around the loop created.
I use momentum & kinetic energy when describing Lorentz force. An E field can change both, but a B field can only change momentum, not KE.
Even if you argue it is a pulse and it is EM that consist of E field. If you put the loop on xy plane and the mag field is in z direction, the E field is propagating in z direction also because even though it is quadriture to the mag field, the direction of propatation still perpendicular to the loop. The loop being perpendicular to z direction will not be affected by E field in z direction. Remember induced E field is alway opposite to the external E field.
Did I help, or make matters worse?

Claude

I don't think the Lorentz law apply. THe only law in play is FL which is the induced voltage.

 

[yungman]

I was going to put in my comment on the professor's video. It was closed, or else I'll give him a piece of my mind.

 

[cabraham]

I don't think the Lorentz law apply. THe only law in play is FL which is the induced voltage.

Lorentz' law does apply. How can it not apply? If loop is immersed in a time varying mag field, it is also subjected to a time varying elec field. E & B are normal in space. The free electrons in the loop are acted upon by the E force. Once in motion the B force is incurred normal to the E force. Otherwise, how can the electrons ever start moving? In order to accelerate an electron you need an E field. Whenever a time varying B is present, so is E present. Under time changing (dynamic) conditions, neither one can exist independently. The E force can change not only the electron's direction, but its speed & KE as well. The B field can only change the electron's direction, & only if the electron is already moving.

Once the E field accelerates the electron, it is not random motion, but drift along the direction of the E field. The mag field B, acts upon the electron normal to its velocity. So, Lorentz law applies here. Otherwise, how would the electrons ever start moving? I can't believe that you don't see Lorentz' law as in effect here. Please elaborate. What gets the electrons initially moving if not Lorentz force? Just asking.

Claude

 

[yungman]

Lorentz' law does apply. How can it not apply? If loop is immersed in a time varying mag field, it is also subjected to a time varying elec field. E & B are normal in space. The free electrons in the loop are acted upon by the E force. Once in motion the B force is incurred normal to the E force.

Read the FL, E induced in the loop caused by B is not the same as the E that accompany the B. THis induced E is not the same as in the Lorentz equation. You have to be very careful about this. Vary B alway have E accompany along and is quad to the B, but this is perpendicular to the induced E in the loop. Only the B portion act on the loop.

Otherwise, how can the electrons ever start moving? In order to accelerate an electron you need an E field. Whenever a time varying B is present, so is E present. Under time changing (dynamic) conditions, neither one can exist independently. The E force can change not only the electron's direction, but its speed & KE as well. The B field can only change the electron's direction, & only if the electron is already moving.

Once the E field accelerates the electron, it is not random motion, but drift along the direction of the E field. The mag field B, acts upon the electron normal to its velocity. So, Lorentz law applies here. Otherwise, how would the electrons ever start moving? I can't believe that you don't see Lorentz' law as in effect here. Please elaborate. What gets the electrons initially moving if not Lorentz force? Just asking.

Claude

If you think of the loop is on the xy plane center at origin, the external EM field in +z direction, the EM is perpendicular the the loop. The E in the EM that propagate in +z direction is perpendicular to the loop and has NO effect on whatever E in the loop.

Remember induced E by an external E is always opposite in direction only. That is the reason we have the FL that stated only the B is in action to cause the induced E. There are two E here, you have to be careful not fixing them up.

 

[cabraham]

If you think of the loop is on the xy plane center at origin, the external EM field in +z direction, the EM is perpendicular the the loop. The E in the EM that propagate in +z direction is perpendicular to the loop and has NO effect on whatever E in the loop.

Remember induced E by an external E is always opposite in direction only. That is the reason we have the FL that stated only the B is in action to cause the induced E. There are two E here, you have to be careful not fixing them up.

Maxwell says otherwise. If the B is normal to the loop (x-y plane), then the E is in the x-y plane. You've placed both B & E on the z axis, which opposes Maxwell.

Either form of ME applies, integral or differential. For the diff form (or "at a point" form):

curl E = -dB/dt.

If B is non-zero & time varying, then curl E is non-zero as well. For that to happen, E is non-zero, since the curl of a zero vector is zero. This E field exerts a force on a free charge resulting in motion of said charge. In order for charge to circulate in x-y plane, E must have a component in x-y plane. Using your established reference with B along z axis, the curl of E is along the z axis only for E in the x-y plane.

Hence, E produces a force upon free electrons in the loop. Once they are in motion, they are subjected to the force due to B as well in addition to E.

Have I overlooked anything?

Claude

 

[yungman]

Maxwell says otherwise. If the B is normal to the loop (x-y plane), then the E is in the x-y plane. You've placed both B & E on the z axis, which opposes Maxwell.

Either form of ME applies, integral or differential. For the diff form (or "at a point" form):

curl E = -dB/dt.

If B is non-zero & time varying, then curl E is non-zero as well. For that to happen, E is non-zero, since the curl of a zero vector is zero. This E field exerts a force on a free charge resulting in motion of said charge. In order for charge to circulate in x-y plane, E must have a component in x-y plane. Using your established reference with B along z axis, the curl of E is along the z axis only for E in the x-y plane.

Hence, E produces a force upon free electrons in the loop. Once they are in motion, they are subjected to the force due to B as well in addition to E.

Have I overlooked anything?

Claude

You keep talking about the induced E in the loop. The external EM in +z direction has the component of E that is in +z direction and has no effect on the loop. You kept talking about varying B has E, this external E is not the induced E and is in +z direction.

The induced E in the loop is purely caused by the external B only. We are talking about two different E fields here.

Yes, the induced E in the loop cause the electrons to run, but that is because of the external B, and this the very essence of FL, not Lorentz.

 

[yungman]

To avoid confusion, I upload a drawing which show Lorentz force:

\vec F = q ( \hat z E_{(x)} +\vec u X \hat z H_{(y)})

Where the \hat z E_(x) \;&\; \hat z H_{(y)} are the electromagnetic wave.

The induced E is \; \vec E_{EXT} \;=\; \hat {\phi} E_{(r)} \; as shown.

As you can see, \hat z E_(x) is normal to the loop and has no effect.

It would be opposit if instead of the loop, we have a straight wire in z direction. In this case, the E assert force on the electrons inside the wire, but here, the B has no effect because B is parallel to the wire.

 

[cabraham]

To avoid confusion, I upload a drawing which show Lorentz force:

\vec F = q ( \hat z E_{(x)} +\vec u X \hat z H_{(y)})

Where the \hat z E_(x) \;&\; \hat z H_{(y)} are the electromagnetic wave.

The induced E is \; \vec E_{EXT} \;=\; \hat {\phi} E_{(r)} \; as shown.

As you can see, \hat z E_(x) is normal to the loop and has no effect.

It would be opposit if instead of the loop, we have a straight wire in z direction. In this case, the E assert force on the electrons inside the wire, but here, the B has no effect because B is parallel to the wire.

In an e/m wave, E & H (B) are normal. I'll double check tonight, but I'm perplexed by your inference that the external B & E fileds are both along the z axis. For a transverse e/m wave, E & H/B are perpendicular to each other, not coincident. I'll get back later.

Claude

 

[yungman]

In an e/m wave, E & H (B) are normal. I'll double check tonight, but I'm perplexed by your inference that the external B & E fileds are both along the z axis. For a transverse e/m wave, E & H/B are perpendicular to each other, not coincident. I'll get back later.

Claude

EM always goes in pair and field has to propergate along the z- axis in his experiment. Yes the E and in the EM wave are normal to each other, they just propagate in z direction.

Also you can look at it this way, \hat z E_{x} is occilating along x direction and it affect the loop both directions and the result cancel out and will not push electron either direction. Only the magnetic field moving the electrons by inducing the electric field along the loop. as shown in arrow on the loop.

I am no expert in EM, this is my understanding. I would not dare to challenge the professor's knowledge on EM, I challenge him on his set up where he drawn the conclusion.

 

[yungman]

In an e/m wave, E & H (B) are normal. I'll double check tonight, but I'm perplexed by your inference that the external B & E fileds are both along the z axis. For a transverse e/m wave, E & H/B are perpendicular to each other, not coincident. I'll get back later.

Claude

You have a chance to look into this? I am no expert in EM, that is my understanding and I am willing to be wrong and learn.

 

[cabraham]

Yes I did look. For a transmission line (2 wire, parallel or coax), the wave propagates in TEM (transverse electromagnetic) mode. So does a space wave. But for a waveguide, TE (transverse electric) & TM (transverse magnetic) modes exist, no TEM mode at all takes place.

For TEM mode, if wave propagation is along z axis, then E is in x axis, & H is in y axis, or any orientation in x-y plane normal to each other. For TE mode, propagation remains along z axis, E is in x axis, but H is in y-axis & z axis. E is transverse (normal) to prop, but H has 2 components, 1 normal to prop, & 1 coincident with prop. So if wave prop is in z axis, E is in x axis, H is in y & z axes. Only E is transverse to prop direction.

For a TM it's vice versa. So in Prof. Lewin's setup, only the TEM mode takes place. If energy is propagating in z direction, then E & H/B are normal to each other in x-y plane, as well as normal to prop.

"Inducing" an E field into the loop is a colloquial phrase. This E field is present in space regardless of whether or not the loop is there. H & E cannot exist independently under time changing conditions. Sorry to be late responding. Christmas season, shopping, fixing up the house, you know.

Claude

 

[yungman]

Yes I did look. For a transmission line (2 wire, parallel or coax), the wave propagates in TEM (transverse electromagnetic) mode. So does a space wave. But for a waveguide, TE (transverse electric) & TM (transverse magnetic) modes exist, no TEM mode at all takes place.

For TEM mode, if wave propagation is along z axis, then E is in x axis, & H is in y axis, or any orientation in x-y plane normal to each other. For TE mode, propagation remains along z axis, E is in x axis, but H is in y-axis & z axis. E is transverse (normal) to prop, but H has 2 components, 1 normal to prop, & 1 coincident with prop. So if wave prop is in z axis, E is in x axis, H is in y & z axes. Only E is transverse to prop direction.
In the professor's case, it is a TEM because he generate a time varying magnetic field which automatically have E field accompany along from z direction. That is the reason I drew both E and H along the z direction. Your accessment is the same as my drawing, E in x and H in y( which I call E(x) and H(y) in my drawing. but they propergate at z direction. This is just a case of simple transverse electromagnetic wave (TEM) propagate in z direction.
For a TM it's vice versa. So in Prof. Lewin's setup, only the TEM mode takes place. If energy is propagating in z direction, then E & H/B are normal to each other in x-y plane, as well as normal to prop.z direction. In real life, the wave is usually polarized, either circular etc. It is not exactly straight E in x and H in y. But the result is the same as long as it propagate in z direction. So we just keep the discussion as E in x and H in y.

If you look at this way where E varying in x direction through the loop that is on xy plane, the effect cancel out because it affect in +ve x just as much as -ve x direction and the result is no effect on the loop due to the E field propagate up. Still only the H field only in play, which is Faraday's Law only, not Lorentz force.

"Inducing" an E field into the loop is a colloquial phrase. This E field is present in space regardless of whether or not the loop is there. H & E cannot exist independently under time changing conditions. Sorry to be late responding. Christmas season, shopping, fixing up the house, you know.
Yes, the source( external ) E and H cannot exist independently under time varying condition. My point is the E is normal to the resistor loop and has no effect. Therefore I claim only the H is in play and is 100% Faradays law, not Lorentz force.

Claude

That is what I have been driving at all this time that this is nothing more than magnetic induction into a closed loop consist of two resistors. Nothing more and the professor make a big sting out of nothing. AND he is wrong. I am not saying his conservative or non conservative ...well, don't know how other way to put it...BS... is wrong, it is just not in play in his experiment. I still say, it is so obvious that any praticing engineer can spot this mistake he made. I tried to put my comment in and want to challenge him out to join in, but problem is the comment section in youtube is closed. And yes I will confront him if possible. I deal with too many PhDs in my career. They are only human and they make mistake just as anyone else. Only difference, this guy is so arrogant about it. The nerve of him to make a video on youtube. He should at least be humble enough to summit a paper in AIP and let others to have a peer review first, then publish it in AIP instead of making a scene on youtube where 99.99% of the public have no idea what he is talking about and think he actually have something valid.

I wonder whether Sarumonkee have done the new experiment yet!

 

[Studiot]

I don't see the point of this protracted discussion about FL v Lorenz, or the castigating others for their point of view.

I pointed out, way back, that correct application of Kirchoff leads to a simple and unambiguous resolution of the issue.

All Proff Lewin did wrong was to offer an inappropriate version of Kirchoff.
There are many instances in mathematical physics where we can loose something if we equate to zero.

 

[yungman]

I don't see the point of this protracted discussion about FL v Lorenz, or the castigating others for their point of view.

I pointed out, way back, that correct application of Kirchoff leads to a simple and unambiguous resolution of the issue.

All Proff Lewin did wrong was to offer an inappropriate version of Kirchoff.
There are many instances in mathematical physics where we can loose something if we equate to zero.

Not castigating others, just one, the professor because of his arrogance. I think we have a good discussion here and I think we are all very civilize with each other. I think it is very important to establish that FL is in play here to make sure there is a voltage generator or distribute voltage generators in the loop, then everything make sense and KVL apply perfectly in this case...not in all cases, just this one.

 

[hikaru1221]

@yungman: Why does the wave propagate in the z-direction?

 

[Studiot]

not in all cases,

Would you like to provide an example?

 

[yungman]

Would you like to provide an example?

Don't know, some people here said it fail in some cases, all I want to say is I do not defend KVL, I only say KVL hold in this case.

Can you tell me your opinion with my assertion that the whole thing is just FL where a magnetic pulse induce a voltage in the loop and when taking into account of the voltage source, KVL hold.

 

[Studiot]

I explicitly showed how to apply Kirchoff to the problem in hand in my post#100.

I also displayed an example of where FL is inapplicable, but Kirchoff is applicable in my post#32.

Perhaps they were so short they slipped by notice?

To find examples of inapplicability, simply look at the conditions of validity of the theorem or equation or law.

FL requires a changing magnetic field. Hence post#32.

Kirchoff requires a complete loop.

 

[stevenb]

and when taking into account of the voltage source, KVL hold.

Which definition of KVL are you claiming is upheld in Prof. Lewin's example?

The version that the Prof gave was that the sum of potentials around a loop equal zero. Do you understand that the transformer EMF you are calling the lumped or distributed voltage source is not a potential? If you understood this you would not claim his definition of KVL is upheld.

Also, the version of KVL from the other MIT lecture is not upheld in the sense that the starting assumption is not true in this example.

So, this point you are trying to make is unclear to me. Telling us your accepted definition of KVL would help clarify and give us a chance of understanding your points.

 

[yungman]

Faraday’s and Kirchoff’s laws were developed for different circumstances and are therefore different.
Both sometimes apply to situations not covered by the other; neither is a special case of the other.

I am in general agreement with Prof Lewin in his statements, with the exception that I have no trouble applying the original form of Kirchoff’s law to his apparatus.

It is instructive to consider the original form of both laws to see where they overlap and where they differ. It should be remembered that in their time magnetism was treated in terms of ‘lines of force’.

This is Maxwell’s translation of Kirchoff



They went on to state that this sum is known as the total EMF in a circuit (loop).


And this is Nightingale's record of Faraday



My understanding of Faraday's law is that it is in differential form as stated here. It is more far reaching than Kirchoff’s Law as it connects electric and magnetic effects. Kirchoff 's Law relates purely to electric effects. However the downside of this is that there must actually be magnetic flux to vary to yield the EMF.

Further differences are that Faraday does not require a closed loop, although he does not prohibit one either.
Kirchoff’s treatise concerned loops in meshes. He does not actually mention potential difference or drop and he does not distinguish between sources of EMF. They are all the same to him.

So to apply Kirchoff to Lewin proceed as follows:

The sum of the EMF's = The sum of the IR products

Used in this form it appears to me that the law is satisfied.

The total EMF in the circuit is 1 volt (the EMF induced by the coil) and the IR sum is 0.9 + 0.1 volt.

I believe it used to be phrased in this way to allow for just such a situation.

What has Lewin done then?

Well there is only one source of EMF in the loop and it is distributed around the whole loop. It is not lumped into any particular circuit element and cannot be applied at any particular point in the loop.
I think we are in agreement on this point that the mag field induce emf into the loop and is distributed around the whole loop. That was the reason I suggested to do the experiment over with resistors making up the whole loop instead of having long section of wire as part of the loop.
This brings out the difference between EMF (which is distributed around the circuit in this case) and Potential Difference or Potential Drop.
But as I said, the professor specifically said he measure the voltage across the resistors going clockwise and counter clockwise. That is potential. He claimed he can measure different voltages but he took the wire as a single point rather than part of the loop.
So Prof Lewin has demonstrated is that an EMF and a Potential Difference are not two names for the same thing. They are in fact different animals.
I don't even think this is relavent for what he tried to claim. He used the voltage drop as an argument. It is PD that he was using.
The give away clue is in his statement about conservative and non conservative fields.

For PD the line intergral \ointE.dl is zero around the loop.
For EMF it is not.

Another way to look at it is that an EMF is capable of introducing energy into the system, but PD is not.

A third way to look at it is to note that PD's result from the solution of Laplaces equation, EMF's result from the solution of Poissons equation, where there is a forcing function.

I am not disagreeing with you on the points you make, I just disagree with the experiment he used to derive his argument. And the whole point is if the experiment was done wrong, there is no point of going any further and nothing can derive out of what he said. One can not over look the flaud of the experiment and continue the argument of the theory.

 

[yungman]

I explicitly showed how to apply Kirchoff to the problem in hand in my post#100.

I also displayed an example of where FL is inapplicable, but Kirchoff is applicable in my post#32.
Of cause FL is not applicable, there is no external magnetic field. I don't even see your point.
Perhaps they were so short they slipped by notice?

To find examples of inapplicability, simply look at the conditions of validity of the theorem or equation or law.

FL requires a changing magnetic field. Hence post#32.

Kirchoff requires a complete loop.

........