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Re: Current in a wire



S'funny. Not a soul seems to have brought in the relativistic effect
of the slowly moving charge carriers.

Brian W

At 12:43 3/23/00 -0500, Michael Burns-Kauri wrote:
If a steady state exists, then the time derivative of the charge density
is zero. Then, the equation of continuity requires that the divergence
of the current density is also zero. If Ohm's law applies, the
divergence of the electric field is then zero. Gauss's law
(differential form) then implies that the charge density is zero.

Michael Burns-Kaurin

Joel Rauber wrote:

I'm troubled by an aspect of what Don Boys and Beatty wrote:

Don Boys wrote:

These
electrons see a non-zero electric field *due to some excess charge
distributed in a non-uniform way on the surface of the metals*. Articles
should appear shortly
in Physics Teacher and AJP showing the actual distribution of
the charges on the
wires for a few specific circuits.

Beatty wrote:

the idea that because
net-charge *only exists on the surface of the wire*, then CURRENT can only
exist on the surface of the wire, since electric current is a flow of
charge, and there is no charge in an uncharged region of metal.

(N.B. asterisks are my emphasis in the above quotes)

The troubling part is the implication/claim that net charge only resides on
the surfaces of the wire and can not reside to the interior of the wire.
This may be the case for conventional situations but:

My understanding is that that the claim that non-zero net charge only
resides on the surfaces is based on a Gauss' Law arguement that hinges
crucially on the idea that the E field is zero to the interior of a
conductor. The E field is of course manifestly *not* zero to the interior
of the conductor where we have non-zero current. Consequently I see no
fundamental reason why one can not have net charge as well as non-zero
current to the interior of a wire.

Joel Rauber


brian whatcott <inet@intellisys.net>
Altus OK