Re: Confused by a derivation.

[David Bowman <dbowman@TIGER.GEORGETOWNCOLLEGE.EDU>]

Regarding John Mallinckrodt's comment:
> ...
> 1 that we genuinely do have planar symmetry, i.e., there is no
>  fringing field (this is the key), and
> ...
> For real capacitors assumption 1 is violated and the result does
> not hold although the violation is typically quite minor.

Since last year I was able to find the exact expression for the
capacitance to infinity of a thin circular disc, I thought I
might try my hand at trying to exactly solve for the capacitance
of a pair of parallel oppositely charged circular plates so as to
see explicitly and analytically the effects of the fringing field
as a function of the plate separation.  So far I haven't come up
with a solution.  But if I do, I post it.  Maybe the exact solution
is just too hard; we'll see.  So far it's too soon to tell.

David Bowman
David_Bowman@georgetowncollege.edu