Re: electrostatic shielding

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Sun, 4 Feb 2001, Ludwik Kowalski wrote:

> I second Leigh's appeal for somebody (who has access to
> a good program) to perform numerical calculations on the
> distribution of Q over a disk of finite size. I am predicting
> that the percentage of Q, at r>0.9*R, for example, will be
> growing when the disk becomes thinner.

Ludwik,

I think that by "finite size" you really mean to say "nonzero
thickness" and that you mean to compare the fraction of the charge
that is on the "ends" (the two circular portions of the disk
surface) to that on the "edge" (the cylindrical portion.)  If so,
I remain very confident that that fraction on the "edge" will be a
monotonically increasing function of the "thickness to diameter"
ratio for the reasons that I stated in my previous message.  At
the very least, I think it is manifestly evident that virtually
all of the charge resides on the "edge" of a long thin wire which
is nothing more than a VERY thick disk.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm