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Re: How many volts ?



Ludwig wrote:
* * *
Bob Sciamands wrote:

You're going to have a tough time getting the field inside these plates
to be zero!

He was responding to

.... Thus an isolated circular plate of very large radius will create
the field which is the same as that due to a uniform circular loop
(a thin wire).

Yes, this is not than what I wanted to say. Let me correct it now.

Thus an isolated circular plate of very large radius will create
a charge density (on both sides) which increases with the radius.
Why should this interfere with E=0 inside a circular plate?

As you can see, Bob, I am waving hands hoping that somebody will prove, or
disprove, my intuitive argument about a single isolated plate. I suspect
that the minimum potential energy will correspond to an axially symmetric,
but not uniform, distribution of initial charge on a single plate. But I
do not know what to think about the final distribution of charges (when
plates are very close to each other). Why should we take it for granted
that the minimum energy requirment, when |Q1| and |Q2| are not equal, is
the same as for equal charges (for two uniform distributions)? I would
like this to be demonstrated (experimentally, analytically or numerically).

Ludwik Kowalski kowalskiL@alpha.montclair.edu
* * *

Ludwig,
There are two different arguments that the isolated, charged,
infinite conducting sheet is uniformly charged (also applicable to
the two, unequally charged sheets of conductor):

1)Symmetry: on the infinite sheet, all points are equivalent and
indistinguishable from one another.

2) The uniqueness theorem of LaPace's equation plus boundary conditions:
Since the uniform charge solution works, it is the only solution.

Bob Sciamanda sciamanda@edinboro.edu
Dept of Physics
Edinboro Univ of PA http://www.edinboro.edu/~sciamanda/home.html