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Re: Toward the equilibrium



Using Maxwell's equations, the continuity equation , and the definition of
conductivity, texts routinely derive an exponential decrease of rho in a
region of constant conductivity. The relaxation time is shown to be
epsilon/conductivity. If memory serves, this is about 10^-19 sec for
copper. This is the simple, classical model, and even ignores mean free
path considerations.

Bob

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

----- Original Message -----
From: "Ludwik Kowalski" <KowalskiL@MAIL.MONTCLAIR.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Wednesday, January 03, 2001 05:28 PM
Subject: Toward the equilibrium


Suppose that at t=0 a charge of 1 microC is deposited at one
point of a copper sphere whose diameter is one meter. I used
to say that "the equilibrium is going to be established very
quickly, perhaps in a couple of nanoseconds or so. Why?
Because it can not be faster than 3.3 ns; the time light
needs to cover the distance of 1 m in air.
. . .
2) How to calculate the time needed to establish equilibrium?
I suspect it is much longer than ~3 ns but I do not know how
to estimate it realistically.
Ludwik Kowalski