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When a conductor carries more current on the surface as compared to core, it is due to
Corona
Skin Depth
Skin Effect
Any of the above
Skin Effect
The skin effect is the phenomenon in which an alternating current (AC) tends to flow mostly near the outer surface of a conductor rather than throughout its cross-section. This leads to a reduction in the effective cross-sectional area available for current flow, thereby increasing the effective AC resistance of the conductor.
The skin effect is the phenomenon in which an alternating current (AC) tends to flow mostly near the outer surface of a conductor rather than throughout its cross-section. This leads to a reduction in the effective cross-sectional area available for current flow, thereby increasing the effective AC resistance of the conductor.
╬┤=╧Аf╬╝╧Г1тАЛтАЛ тАФ Skin depth equation representing the distance current density decreases
RacтАЛ>RdcтАЛ тАФ Resultant increase in resistance due to reduced effective area
When AC flows through a conductor, the internal magnetic flux linkages are higher at the center than at the surface, creating higher self-inductance and higher inductive reactance at the core. According to Lenz's law, this higher reactance opposes current flow more strongly in the center, forcing electrons to migrate towards the low-reactance surface region. The depth at which current density drops to 1/e (approx 37%) of its surface value is known as skin depth (╬┤).
Skin effect increases with higher frequency (f), higher permeability (╬╝), and higher conductivity (╧Г).
It is negligible in DC circuits where f=0, resulting in uniform current distribution.
For power transmission, skin effect is managed using ACSR (Aluminum Conductor Steel Reinforced) cables.
The effective resistance of the conductor is significantly higher under AC conditions than under DC.
Used in surface hardening of metals (induction heating)
Useful in shielding sensitive equipment from high-frequency interference
Increases I2R power losses in transmission lines
Reduces the ampacity (current-carrying capacity) of conductors
AC Transmission lines
High-frequency waveguides
Induction heating processes
Skin depth ╬┤ is inversely proportional to the square root of frequency.
Option A (Corona) refers to air ionization near conductors due to high voltage stress. Option B (Skin Depth) is the measure of the effect, while Option C (Skin Effect) is the phenomenon itself.
C is correct тАФ The phenomenon of current concentration on the conductor surface due to non-uniform current distribution is known as the Skin Effect.
Always remember that skin effect is absent in DC, making it a critical differentiator in Transmission Line Performance exams compared to DC distribution.