Re: funny capacitor

["RAUBER, JOEL" <JOEL_RAUBER@SDSTATE.EDU>]

I must make a small nit-picking exception to what John wrote below:

> There is nothing special about the "point" at "infinity".  In
> particular,
> Laplace's equation doesn't know (or need to know) whether
> there is any such
> place as "infinity".  Laplace's equation, including gauge(t)
> invariance,
> applies just fine in a universe with periodic boundary
> conditions, in which
> case there obviously is no such place as "infinity".

There is something *special* about "infinity".  It is the location where you
may place an object and not have it be affected by how you manipulate the
charges on (and only on!) the nearby conductors.  This is exactly one of the
points Bob has been making.  However, I agree with John that this *special*
fact about infinity is not necessary at all for the funny capacitor thread
for all the reasons of gauge invariance that John has illucidated.

Joel Rauber