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Re: Current in a wire



John,

At very high frequencies there is a "skin effect" that restricts the
current to the surface of the wire. The "free" charge indeed does respond
to the fields in the wire (but never really moves very far on the average).
At low frequencies (normal household alternating current), the skin effect
is negligible.

Mark Shapiro
http://www.IrascibleProfessor.com

-----Original Message-----
From: John P Lewis [mailto:jlewis@GLENBROOK.K12.IL.US]
Sent: Wednesday, March 22, 2000 1:45 PM
To: PHYS-L@lists.nau.edu
Subject: Current in a wire


Hi Folks,
I'm in a bit of confusion now about the movement of charge (electrons) in a
wire. My belief is that if a wire were connected to some sort of emf
current should flow throughout the entire wire. I have a colleague in
electronics who maintains that the charge travels only on the exterior
surface of the conductor.
As I think of the stranded wire in my house I think of speaker wire etc that
might experiece a high frequency alterration of the emf and thus current,
does most of the charge that moves at high frequency prefer the external
surface of the wire?

And what about resistance being proportional to the cross sectional area.
Shouldn't that support the concept that the field is set up throughout the
conductor?

Please forward any thoughts on the issue. Thanks.

John