Lecture 8: Polarization, Dielectrics, The Van de Graaff, More on Capacitors
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008, recorded: February 2002, views: 2642
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)
Download slides: dielectrics_and_polarization.pdf (162.0 KB)
Download mit802s02_lewin_lec08_01.m4v (Video - generic video source 106.0 MB)
Download mit802s02_lewin_lec08_01.rm (Video - generic video source 81.3 MB)
Download mit802s02_lewin_lec08_01.flv (Video 190.6 MB)
Download mit802s02_lewin_lec08_01.wmv (Video 448.7 MB)
Report a problem or upload filesIf you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
"Electric fields can induce dipoles in insulators.
Electrons and insulators are bound to the atoms and to the molecules, unlike conductors, where they can freely move, and when I apply an external field -- for instance, a field in this direction, then even though the molecules or the atoms may be completely spherical, they will become a little bit elongated in the sense that the electrons will spend a little bit more time there than they used to, and so this part become negatively charged and this part becomes positively charged, and that creates a dipole.
I discussed that with you, already, during the first lecture, because there's something quite remarkable about this, that if you have an insulator -- notice the pluses and the minuses indicate neutral atoms -- and if now, I apply an electric field, which comes down from the top, then, you see a slight shift of the electrons, they spend a little bit more time up than down, and what you see now is, you see a layer of negative charge being created at the top, and a layer of positive charge being created at the bottom.
That's the result of induction, we call that also, sometimes, polarization. You are polarizing, in a way, the electric charge..."
Link this pageWould you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet !