Re: Electric Field Question

[Gary Turner <turner@MORNINGSIDE.EDU>]

On Tue, 5 Feb 2002 15:06:26 -0800, kowalskil <kowalskil@MAIL.MONTCLAIR.EDU>
wrote:

> P.S.
> It seems that two concentric shells with net charges +Q and +Q
> (or -Q an -Q) represent a charged capacitor. Why not? There
> is an electric field between the two equally charged electrodes.
>
> Will the system be discharged by touching the electrodes
> with a conducting rod, for example, by somebody sitting on the
> surface of the smaller shell? It depends on what is meant by
> "discharged." The rod will allow the positive charge to move
> from the the smaller shell to the outer surface of the larger
> shell. The field between the electrodes will disappear. The
> inner shell will become neutral but the charge on the outer
> shell will double. And somebody outside the system will continue
> observing a constant E = k*(2*Q)/r^2. How would he know
> that these processes occured inside?
>
> A spherical capacitor with two equal charges of the same sign?
> It would be confusing to call such setup a capacitor. What would
> be a better name?" I would say that the word "capcitor" is
> reserved for a setup with two equal charges of opposite sign.
> Ludwik Kowalski
But that is really what you have.  The external surface of the internal
sphere will be positively charged, the internal sphere of the external
shell will be negatively charged (to 'absorb' the field lines) and the
external surface of the external sphere will have a double-positive charge
(or interchange pos for neg throughout).  The 'capacitor' exists between
the spheres, and is still bounded by oppositely charged plates.
Surrounding that is a layer of positive charge, but that has no bearing on
the capacitor.

Just my $0.02



P.S.  Some of you have some really nice sig files.  How do you include a
signature?