Skin effect is only seen in AC, not DC.
Understanding Skin Effect
Skin effect describes the tendency of alternating current (AC) to distribute itself unevenly within a conductor. Instead of flowing uniformly throughout the cross-section, the current concentrates near the surface of the conductor. This is due to the opposing electromagnetic forces induced by the changing magnetic field of the AC current. These induced currents create a counteracting force that pushes the primary current towards the outer layers.
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AC: The changing magnetic field in an AC circuit induces eddy currents within the conductor. These eddy currents oppose the main current flow, leading to the concentration of current near the surface – the skin effect.
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DC: In a direct current (DC) circuit, the magnetic field is constant. There are no induced eddy currents to oppose the current flow. Therefore, the current distributes uniformly throughout the conductor's cross-section. The skin effect is negligible.
The provided reference states: "Skin effect is the result of induced changing currents in a conductor core. In AC there is back emf and thereby skin effect. So skin effect is only seen in AC and not in DC." This accurately summarizes the phenomenon.
The skin depth, the distance from the surface at which the current density falls to 1/e (about 37%) of its surface value, is directly related to the frequency of the AC current. Higher frequencies lead to a smaller skin depth, meaning the current is even more concentrated near the surface.
