MadSci Network: Physics
Query:

Re: Does an electric current flow through a wire or the surface of the wire.

Date: Tue Apr 10 15:44:13 2001
Posted By: Barry Kamrass, Consulting Engineer
Area of science: Physics
ID: 986577557.Ph
Message:

Sorry, but an electric current flowing through a wire mostly flows on the 
surface, not the interior of the wire.  The reason for this is that 
electrons repel each other, so they want to get as far away from each other 
 as they can.  This is called "skin effect".  Current flowing through a 
wire *does* penetrate the wire to a certain depth, called the "skin depth". 
 The fact that current flows mostly on the surface of the wire leads to an 
increase in wire resistance at higher frequencies.  Therefore, there's a 
type of wire called "Litz Wire" which consists of many small insulated 
strands of wire woven into a cable form.  This is used to get the minimum 
possible resistance when driving a current through a wire.

Reference:  Ramo, Whinnery, Van Duzer, "Fields and Waves in Communication 
Electronics", available at any college library.


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