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Re: electrostatic shielding

Fred, you have been lurking in my brain.
It was just considerations of such charge near a sheet conductor that led
me to at first believe that the outer charge distribution might change
when only the interior, imposed charge was moved in the hollow conductor
case. I now see that there are serious pitfalls in taking this to be some
limit of a charge inside an (very large) large sphere.

I am now convinced that arguments based on the uniqueness theorems (ala J.
Mallinckrodt) can be marshalled (with care) toward a rigorous proof that
regardless of the geometry, moving only the interior, imposed charge will
not affect the outer charge layer distribution in the hollow conductor
situation.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: "Lemmerhirt, Fred" <FLemmerhirt@MAIL.WCC.CC.IL.US>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, February 02, 2001 09:48 AM
Subject: Re: electrostatic shielding


I guess John Mallinckrodt's reminder of the uniqueness principle finally
provides a convincing requirement that the charge on the outside of the
sphere must remain uniformly distributed, provided that rearrangement of
the
inner surface charge alone can cancel the off-center point charge's
field
within the conducting shell. (As Bob Sciamanda pointed out, no one here
seems to have shown that this is possible, but it surely seems
reasonable.)

Now can I extend this result to another situation?:

Suppose a very large isolated flat conducting sheet carries a net
negative
charge. Will the charge be uniformly distributed on both surfaces,
producing a uniform field pointing straight toward the sheet on both
sides?
And if a positive point charge is brought near one side of the sheet,
will
the charge only on that side of the sheet be rearranged and the field on
that side "distorted", while the charge and field on the opposite side
remain uniform?

______________________________________
Fred Lemmerhirt
Waubonsee Community College
Sugar Grove, Illinois
flemmerhirt@mail.wcc.cc.il.us <mailto:flemmerhirt@mail.wcc.cc.il.us>
http://chat.wcc.cc.il.us/~flemmerh/physics.html
<http://chat.wcc.cc.il.us/~flemmerh/physics.html>