Lecture 16: Electromagnetic Induction, Faraday's Law, Lenz Law, Complete Breakdown of Intuition, Non-Conservative Fields

author: Walter H. G. Lewin, Center for Future Civic Media, Massachusetts Institute of Technology, MIT
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008,   recorded: February 2002,   views: 69783
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)

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Reviews and comments:

Comment1 Janette Wilmott, February 23, 2009 at 12:54 p.m.:

I feel as if I have struck gold tonight - finding this lecture. Thank you Prof Lewin. This has increased the currency of my physics.

Comment2 Fawzan Dinnunhan, July 28, 2009 at 11:29 a.m.:

Awesome finally i understand what my teacher at school was trying to say

Comment3 Deepu, October 20, 2009 at 5:21 p.m.:

Mind blowing!!!!
Not sure if Faraday could explain his theory the way you do...U R really Excellent, Prof. Lewin.
And thank you very much for the video, it has really helped me alot in the understanding of Faraday's law.

Comment4 kyle thomas, June 9, 2010 at 8:57 a.m.:

This is an incredible resource and I feel blessed to benefit from these pioneering efforts to make educational materials freely accessible to the masses. There is a small error in converting cm^2 to m^2 at about 47 minutes into the video. 10[cm^2] = 10^-3[m^2]

Comment5 Tim Hidecker, February 18, 2011 at 9:05 p.m.:

This guy is wicked smot.

Comment6 Joe Sans, March 14, 2011 at 8:07 p.m.:

Excellent lecture. Precisely, what is induction? Where do the electrons come from as the magnetic field lines sweep over a coil. When I took college level physics it was never explained how the electrons appear in the circuit. No one is able to explain to me. Do they originate at the quantum level and then appear on the atomic scale — the level of the atom. Can someone explain that or give me a reference that addresses that.

Please help me understand.

Thanks Joe Sans

Comment7 munawar kholil, November 25, 2011 at 8:43 a.m.:

This video is petrified for me, thanks.
if there was video of the waveguides is my hope

Comment8 Lovro Marković, December 3, 2011 at 11:42 a.m.:

@Joe Sans:
Electric conductors (e.g. metals) are materials which have 'loose', or free electrons moving about in the material.
Now, atoms in metals do not form covalent nor ionic bonds, but METAL bonds, in which all of the atoms 'share' a giant electronic cloud.
It's like Thomson's plum pudding: you have a lot of positive atomic cores immersed in electrons which they gave up.
When there is a electric potential difference between the two ends of a conductor, the electrons won't move around chaotically and loosely anymore, but in a directed path (to the positive end).
Now, at the beginnings of electricity experiments, physicists thought there was a positive charge moving, but now we know those are negatively charged electrons.
They kept that concept, so the flow of charge, or electric current is therefore depicted as the flow of positive charges to the negative end of the conductor.
In the end, it all mathematically ends up correct.

Comment9 Gary, December 7, 2011 at 4:42 a.m.:

I have always had issues with eggheads that don't speak English or like to pretend to be smarted than they really are, this guy jsut explained in a few minutes what I never understood for over 20 years.
Maybe I do need pictures or examples to learn something, but it's better than reading a Law and just repeating it word for word while not understanding it and avoiding to admit I can't explain it or produce a picture or it in action.

Comment10 J. Sethuraman, March 29, 2012 at 6:02 p.m.:

Great professor, Dr. W. Lewin. Mind blogging concept of
non-conservative electric field. Simply thrilled. Yes, I will tell my grand children thro' my son.
J. Sethuraman

Comment11 Ebrahim saffari, May 28, 2014 at 1:04 p.m.:

Dear Sir.
I am urgently in need of having Prof. Walter Lewin lecture on subject polarization & dielectric both video and script.unfortunately it is filtered in Iran.How can i get rid of filtering.is it possible to get script of lecture?

Comment12 Mina Metcalfe, March 11, 2016 at 9:55 p.m.:

Professor Lewin, This is a wonderful, clear and exciting lecture. Thank you for presenting electromagnetism so extremely well. It has been an absolute delight to find your lectures online.
I love the way you add in experiments to illustrate your points. The theory alone can be dry and difficult. You make it seem easy, and also great fun.
Thank you so much. This work is truly great.
One question:
I do not quite see how one can attach a voltmeter in 2 different ways to points A and D, to get the results to differ. I do appreciate the theory, that the line integrals give a different result by different paths from A to D. But how does a voltmeter know which path it is meant to be measuring, if it's attached to A and D?

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