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Skin Effect in Conductors

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When a conductor is carrying dc current , it is uniformly distributed over the cross section of the conductor . However an alternting current flowing through the conductor does not distribute uniformly, rather it has the tendency to concetrate near the surface of the conductor. This is known as Skin effect.

  Thus, skin effect is the tendency of an alternting current to concentrate near the surface of the conductor.


   
Due to skin effect the effective area of cross section of the conductor through which current flows is reduced consequently, the resistance of the conductor is slightly increased when carrying an alternating current.

Cause of skin effect

The cause of skin effect can be easily explained. A solid conductor may be thought to be consisting of a large number of strands, each carrying a small part of current. The inductance of each strand will vary according to its position. Thus, the strands near the centre are surrounded by a greater magnetic flux and hence have larger inductance than that near the surface. The high reactance of the inner stranded causes the alternating current to flow near the surface of conductor. This flowing of current near the conductor surface is the skin effect.

The factors on the skin effect depends:-
i, Nature of material.
ii, Diameter of wire- directly proportional.
iii, frequency- directly proportional.
iv, Shape of wire- less for stranded conductor than the solid conductor.

Note: Skin effect is negligible for frequency less than 50HZ and conductor diameter less than 1 cm.

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