Conduction in (or on) a wire

  • Thread starter middling
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  • #1
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Main Question or Discussion Point

I quote from Oliver Heaviside, "Electromagnetic Theory", 1893, p.15:

It was discovered by mathematical reasoning that when an electric current
is started in a wire it begins entirely upon its skin, in fact upon the outside
of its skin; and that, in consequence, suficiently rapidly impressed fluctuations
of the current keep to the skin of the wire, and do not sensibly penetrate to
its interior.

Is this true?
 

Answers and Replies

  • #2
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As the quote says, this is true for fluctuating currents; in other words, it is true for AC, but not for DC.

At zero frequency (DC) the current occupies the entire cross section of the conductor, as you start increasing the frequency, the current starts to empty the conductor from the center effectively turning into just an annular conducting cross section.

Google "Skin effect" or "skin depth".
 

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