Re: Conserving Q/Faraday

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

Responding to:

> At 23:41 1/25/99 +0100, you wrote:
> > ... Suppose that a net charge is really
> > present in the dielectric slab of a capacitor connected to HV. How
> > can this net charge possibly be revealed? ...

brian whatcott wrote:
> >
> One method has already been mentioned in this thread:
> the demonstration of charge recovery in a discharged capacitor.
I do not see how it can help. Recovery is consistent with the charge
penetration idea of Faraday (what was pushed into the dielectric comes
back), not with the NET Q (more electrons on one side than on another).
I assume you are referring to the reappearance of the d.o.p. after the
plates were "discharged" with a wire.

Actually, one may be able to explain the recovery without a model
in which free charges travel to and from the metallic electrodes.
Consider a dielectric whose permanent dipoles are aligned by E.
You "discharge" the capacitor but the dipoles are still aligned,
unless the temperature is too high. In that case + and - Q are
induced in the metallic electrodes by layers of bound charges.
Thermal agitation tends to disorient dipoles resulting in slow
disappearence of the layers. But free charges have nowhere to go
and the d.o.p. reappears gradually between the electrodes.

Ludwik Kowalski