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Re: Confused by a derivation.



Ludwik, I think your problem is with your interpretation of the statement
(and derivation thereof) that the field just off a conductor is
sigma/epsilon. This is NOT just the field due to the charge layer on the
conductor surface - it is the field due to the entire universe.
In the Gauss' law derivation of the field off a conducting plate it is
presumed that the field on one side of the surface charge layer (ie.
inside the conductor) is zero. The single charge layer cannot do that
alone - it produces a field on both sides (sigma/2epsilon). The rest of
the universe contributes so as to reduce the field inside the conductor to
zero. So it is the total (universe's) field that is being calculated in
this application of Gauss' law.

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