M.I.T.-Walter Lewin- Complete Breakdown of Intuition - Part1

What people said

Recommends Kyle Kanos · 2014-09 · Physics Stack Exchange · on “Application of Kirchhoff's laws in circuits with inductors”

Typically, with inductors, we use the complex impedance [LINK] , $Z=i\omega L$ with current frequency $\omega$ and inductance $L$, for the voltage: $$ V_{ind}=IZ,\quad V_{rms}=I_{rms}|Z| $$ where the left equation is the voltage of the inductor and the right equation the root-mean-square. Surely, however, what goes on inside the inductor doesn't matter, it only is only the voltage drop across the inductor that actually matters with Kirchoff's voltage law. Kirchoff's current law, on the other hand, states that the current across a complete circuit is zero because otherwise a charge builds up, so again the non-conservative field is irrelevant. Professor Lewin (MIT) explains [this video] that if we

Recommends Floris · 2015-03 · Physics Stack Exchange · on “Em induction, sliding rod with resistance?”

Are you sure that the numbering of $R_1$ and $R_2$ in your diagram is the same as in the answer key? It seems to me that it is more conventional to label the first resistor (the one on the left) $R_1$. The equations you wrote appear to me to be correct: the current is indeed given by the e.m.f. divided by the series resistance, and the voltage developed across each element must be equal to the current times the resistance. Having said that - these problems are often tricky, and I have run into problems with them myself. There is a famous Walter Levin lecture on a similar topic - see [this video] . Mind blowing.

Recommends Farcher · 2018-08 · Physics Stack Exchange · on “Inductor in A.C. Circuit”

@GokulakrishnanShankar If the work done between two points is not independent of the path taken then the field is non conservative. Have a look at this video. [this video]

Recommends naturallyInconsistent · 2023-12 · Physics Stack Exchange · on “Confused about sign of mutually induced EMF when applying KVL”

I finally have some time to type this up, and show you how and why KVL is just the wrong way to deal with this. Faraday's Law is, with minus sign as the Lenz's Law, $$\tag1\oint_{\partial S}\vec E\cdot\vec{\mathrm d\ell} =-\frac{\mathrm d\ }{\mathrm dt}\iint_S\vec B\cdot\vec{\mathrm d^2A}$$ Note that the LHS is an integration over the electric field, and the RHS is an integration over the magnetic field. This is a statement of a relationship between two different phenomena, and should be kept as such. Now, let us apply Faraday's Law to the middle circuit. Integrating clockwise starting from the switch, the first contribution is the electric field inside the battery, and we are traversing fro

Cites spraff · 2012-06 · Physics Stack Exchange · on “Explaining Walter Lewin's "Complete Breakdown of Intuition"”

This Walter Lewin [this video] lecture hinges on the solenoid producing a non-conservative field. I read in the Feynman Lectures that "all the fundamental forces in nature appear to be conservative" (Vol 1, 14.5) which comes decades after Faraday's Law of Induction so surely he would have known about it. 1) Who is right? Or, what did Feynman really mean? 2) In Lewin's final diagram there are two voltmeters which, apart from a section of wire, attach in the same place. What happens as you bring the two attachment points together to meet? I can't see, in a physical on-the-table experiment, how one voltmeter is "measuring in the other direction".

Cites Val · 2013-04 · Physics Stack Exchange · on “measuring electromagnetic induction”

There is a famous law [LINK] which says that a potential difference is produced across a conductor when it is exposed to a varying MF. But, how do you measure it to prove? It is quite practical. Particularly, I had once a problem developing a power supply. When transistor rapidly opened a loop of powerful current, I had very strange effects and discovered that there is a voltage difference across the same wire, without any resistor between the probing points! The longer was the distance between probes, the higher was the voltage. Then I have realized how the real the law is. But, what I could not understand if the voltage were spikes induced in the wire indeed or they were purely fictional,

Cites Diracology · 2016-05 · Physics Stack Exchange · on “Does topology have any role in classical physics?”

I would like to add two concrete examples where topology plays a major role in classical and perhaps every day physics. The topologic relevance here is that in both examples the space non simply connected and that makes all the difference. The references are in the titles below. Aharonov-Bohm analogue in water waves [LINK] : This was proposed and also verified by Michael Berry (Berry's phase). The idea is to drain a large bathtub filled with water in such a way that a vortex is formed. This vortex makes the space (the water) non simply-connected. The water flow is irrotational but with non vanishing circulation. Check again this [LINK] for the explicit vector field having this property. Now

Cites lineage · 2021-06 · Physics Stack Exchange · on “Voltage across voltage source in a short circuit”

Your setup is self contradictory: When we short-circuit a voltage source That means the voltage source is no more - its shorted after all. You can't short two terminals and still say they have a potential difference. Applying KVL then gives, $0_{\text{sum must be zero}}=0_{\text{no potentials}}$ which is trivial but consistent. How can it be $0 V$ if we have a voltage source? It can't. But again, a shorted voltage source isn't one at all. What about real life batteries which involve internal resistances? Surely there is some contradiction there? No. Applying KVL gives $0=V_{ideal}-I R_{internal}$ where $V_{ideal}$ is the emf of the battery. All the short does is drive a current through the r

Cites user394334 · 2021-09 · Physics Stack Exchange · on “Why is there an electrostatic field in a closed current?”

Yes, I think it is possible to transfer a charge through two different resistors and have different work. : [this video] But it seems that the answer to this question is that we assume that the time-varying magnetic field is zero outside a conductor(lumped element model), so Faradays law says that the field is conservative.

Cites naturallyInconsistent · 2023-05 · Physics Stack Exchange · on “What does KVL imply about about phasors in an AC circuit?”

@JánLalinský I cannot help the lot of you who are explicitly intending to get it wrong. There is absolutely no need to defend KVL either---Faraday's Law is KVL with correction, so that it would be the correct drop-in replacement whenever KVL is placed. And for the fact that no potential is useful, let this experiment prove it to you: [this video]