Re: Re:IONS/metal pedagogy

["Bob Sciamanda" <trebor@velocity.net>]

-----Original Message-----
From: Ludwik Kowalski <kowalskiL@Mail.Montclair.edu>
To: phys-L@atlantis.uwf.edu <phys-L@atlantis.uwf.edu>
Date: Sunday, October 11, 1998 5:28 PM
Subject: Re:IONS/metal pedagogy


> The specification "due to the rest of the universe", which appears
> in two Bob's messages, is not clear to me. What is its significance?
> My understanding of the difference between (1/2)*sigma/epsilon and
> (1)*sigma/epsilon has nothing to do with the "rest of the universe",
> only with total charges on the objects under consideration. In the first
> place the field due to sigmas exists on both sides of the surface while
> in the second case the field of sigmas exists on one side only. Am I
> missing something more significant to our debate?
> ...
> Ludwik Kowalski


Hi Ludwig,
In case 1 (field on both sides) you are calculating the field ONLY due to
a single sheet of charge;  put another way, the single sheet of charge is
your gedanken universe.
In case 2 (field zero on one side) you are calculating the field due to
the entire real universe - that's why the field is presumed zero inside
the conductor;  it is only the net field due to EVERYTHING that can be
presumed to be zero inside the conductor.

-Bob

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