Question

Skin effect is shown by
A. DC
B. AC of frequencies < ${10}^3\text{Hz}$
C. AC of frequencies > ${10}^3\text{Hz}$
D. any frequency signal

Answer 1

HintThe above problem can be solved by using the behavior of the varying magnetic field. The direction of the alternating current varies continuously. This varying alternating current produces a varying magnetic field. The variation in the magnetic field creates an electric field in the conductor. This electric field forces the charge in the conductor away from the axis of the conductor and towards the surface of the conductor. The electric field induces the emf in the reverse direction. The effect of the reverse emf is highest at the center of the conductors. The tendency of the charge carries to move along the surface of the conductor is called the skin effect. The skin effect varies according to the frequency of the alternating current. The skin depth is the depth in the conductors from the surface in which the charge carries flows under the minimum effect of the reverse emf.

Complete step by step answer
The skin effect arises due to the varying input signal and the signal does not vary with time in the DC supply, so the DC supply does not show the skin effect and the option (A) is incorrect.
The skin depth in the conductor varies with the frequency of the input supply. If the frequency is low then the skin depth is higher and a large cross section of the wire is needed to flow of charge, so the low frequency does not show the skin effect and the option (B) and option (D) are incorrect.

The skin effect is shown by the high frequency greater than 1000 Hz, so the option (C) is correct.

Note: The input signal of the AC with frequency less than 1000 Hz also shows the skin effect but the skin effect at these frequencies remains smaller and smaller skin effects remain of less importance. The higher skin effect reduces the amount of the material for wires.