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# Re: Charged disk; was electrostatic ...

Let me return to Leigh's cylindrical disk. We want to find
the equilibrated distribution of excess electrons. We begin
with some initial configuration, for example, a uniform
distribution within the volume (all below the surface).
They repel each other at the same time but using a computer
we must deal with them on the one-by-one basis (as it is
done with several satellites, etc.).

Suppose I number electrons from 1 to 100 and start with #1.
I calculate the net force acting on it (by 99 electrons) and
allow it to move "1 mm" along the direction of the net force.
Then I go to #2 and perform the same operation, etc. After
serving all 100 electrons I start over and allow each of them
to move "1 mm". Computer will do this. In principle the
system will evolve toward the equilibrium and we could
see how electrons are distributed after millions of steps.

But there is a snag. What should we do when the surface is
reached? Obviously there must be a new force preventing
electrons from escaping? How should I describe it? I know
that Bob Schimanda has already asked this question in a
more general context. But it was never answered. It is not
an electric force. What kind of "fifth force" is it?
Ludwik Kowalski