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Why does an AC current face the skin depth but DC current doesn't?

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aryajur

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Why does an AC current face the skin depth but not DC current :D ?
 

Kral

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Re: Skin Depth

aryajur,
Skin effect is caused by the back emf produced by the self induced magnetic flux in a conductor. The back emf is proportional to the rate of change of magnetic flux (V = Ndphi/dt). As you move closer to the center of a conductor, the total flux increases, and therefore the back emf increases, thus reducing the current toward the center of the conductor. For a DC current, the rate of change of flus is zero, so there is no back emf due to changes in magnetic flux. Therefore, the current is uniformly distributed trroughout the cross section of the conductor. As the frequency increases, the back emf increases, and therefore more current is crowded toward the outside of the conductor. This is a highly simplified explanation. For a complete analytical soultion, you must resort to Maxwell's equations. For a totally irrational, fantasy-land explanation, read any of the so-called high end audio magazines. They will provide myriad articles by authors that work for audio cable ompanies, willing to sell audio cables made from Litz wire.
Regards,
Kral
 

    aryajur

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aryajur

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Re: Skin Depth

Hey thanks Kral,
Yes I had an explanation in terms of Maxwells equations and that if we have an alternating current it is due to the electromagnetic waves, which decay very rapidly inside a conductor and hence the field is neglegible except on the surface thats why the current flows on the surface.
I was hoping there was some other intuitive explanation. This explanation was good. Thanks.
 

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