Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
If the frequency is increased, then the skin effect will
Decrease
Remain same
Increase
None of the above
Increase
The skin effect is the tendency of an alternating current to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases at greater depths. As the frequency of the supply increases, the depth of penetration decreases, thereby increasing the skin effect.
The skin effect is the tendency of an alternating current to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases at greater depths. As the frequency of the supply increases, the depth of penetration decreases, thereby increasing the skin effect.
╬┤=╧Аf╬╝╧ГтАЛ1тАЛ тАФ represents the skin depth, where f is frequency, ╬╝is permeability, and ╧Гis conductivity.
RacтАЛ=RdcтАЛ├Ч(1+kтЛЕf2) тАФ describes the increase in effective resistance due to skin effect.
The mechanism is governed by eddy currents induced by the changing magnetic field within the conductor itself. At higher frequencies, the rate of change of magnetic flux increases, leading to higher induced back-EMF near the center of the conductor. This opposes the flow of current in the center, forcing electrons to move toward the outer surface (skin) of the conductor.
Skin effect is negligible at DC (f = 0).
It significantly increases the effective AC resistance of transmission lines.
The phenomenon is more pronounced in conductors with high magnetic permeability.
Stranded conductors are often used to reduce the impact of skin effect.
Useful in induction heating and hardening processes
Can be used for surface-only signal transmission
Increases ohmic (I2R) power losses
Reduces the effective current-carrying capacity of the conductor
High-frequency communication lines
Induction furnaces
High-voltage AC transmission
For power frequency (50 Hz) in copper, the skin depth is approximately 9.3 mm.
Option A is incorrect because skin effect does not decrease with frequency; Option B is incorrect as frequency is a primary factor influencing the effect.
C is correct тАФ Increasing the supply frequency increases the inductive reactance near the center of the conductor, forcing the current towards the surface and thus increasing the skin effect.
Always remember that skin effect is directly related to the square root of frequency; thus, even small increases in frequency can lead to measurable increases in AC resistance.