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Re: how many volts ?





On Wed, 26 Mar 1997, W. Barlow Newbolt wrote:

I think that we beginning to make this problem difficult. We can
probably calculate the potential distribution is space due to a flattened
coffee can lid isolated in space with 100nC on it. We can do the same
for one with -10nC on it. The charge will probably be distributed so
that both plates have an excess of charge at the edge. The appropriate
derivatives will yeild the field.

Now we have to move them together. Presumably, the charge distributions
will change and the plates will attract one another during the move. I
have no idea how to model the changes in the potential. Apparently, the
potential at infinity would approach that of a point charge with 90nC and
a capacitor with +10nc on one plate and -10nC on the other. The latter
will probably fall off much faster than the former--does that help?

John already gave a correct solution, much simpler than this, and it got
tidied up a bit by a few subsequent posts which confirmed the logic and
insight. Seems to me the problem as originally given, is done. The
considerations you discuss above simply aren't necessary for doing the
problem as given.

Perhaps someone (John?) should restate the problem and its solution in
polished form with all the necessary insights, so we can close this epsode
and move on to something completely new. It's unclear to me whether some
people are disagreeing with the solution, or the method for obtaining it,
or perhaps some didn't understand it.

-- Donald

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Dr. Donald E. Simanek Office: 717-893-2079
Prof. of Physics Internet: dsimanek@eagle.lhup.edu
Lock Haven University, Lock Haven, PA. 17745 CIS: 73147,2166
Home page: http://www.lhup.edu/~dsimanek FAX: 717-893-2047
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