Re: volume polarization vs. surface charge

["John S. Denker" <jsd@MONMOUTH.COM>]

At 10:23 AM 3/5/99 -0500, Donald E. Simanek wrote that the "sticking" point
is this:
> The surface charge due to polarization of a dielectric is, whether you
> consider it "real" or "virtual", not capable of constituting the charge
> which makes the spark when the capacitor discharges. It isn't
> macroscopically mobile.

Hmmm.  If I understand correctly, the topic of conversation can be boiled
down to two questions:

1) Given that charged particles are moving in one part of the circuit (the
dielectric) and also in another part of the circuit (the spark gap), are
these the *same* charged particles, having traveled from one place to the
other?

2) Does the answer to question (1) tell us anything interesting about the
nature of this circuit in general or capacitors in particular?

My answers to these questions are:

1) Of course not.

2) No, so far as I can tell.

Let me explain:

Consider an ordinary extension cord: 16-gauge copper wire, six feet long,
carrying 1 amp at 60 Hz.  Some electrons go in at one end, and some
electrons come out the other end.  Are these the same electrons?  No.
According to my calculations, all of the electrons involved move only
submicroscopic distances.  It's an easy calculation.

This copper wire exemplifies the role of *free* charges in carrying
current.  Sameness has nothing to do with current-carrying in this case.

Therefore when it is pointed out that for capacitors containing *unfree*
carriers, the input-carriers are not the same as the output-carriers, it is
hard to see why this is interesting or relevant.  It is hard to see why
this tells us anything about the nature of capacitors.

Or have I completely misunderstood what is the topic of conversation?

Cheers --- jsd