1. Nov 25, 2011 #1

   middling

   

   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?

    

   middling, Nov 25, 2011
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3. Nov 25, 2011 #2

   gsal

   

   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".

    

   gsal, Nov 25, 2011

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