The skin effect is negligible with DC (Direct Current); current is distributed relatively uniformly across the conductor's cross-section.
Here's why:
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Skin Effect Defined: The skin effect is the tendency of an alternating current (AC) to distribute itself within a conductor so that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the conductor. In other words, AC flows mostly on the "skin" of the conductor.
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Frequency Dependence: The skin effect is directly related to the frequency of the current. As the frequency increases, the skin effect becomes more pronounced. This is because of the opposing eddy currents induced by the changing magnetic field of the AC.
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DC (Zero Frequency): DC, by definition, has a frequency of zero (0 Hz). Since the skin effect is frequency-dependent, it does not occur with DC. A constant DC current generates a static magnetic field. This field doesn't induce eddy currents and therefore doesn't push the current towards the surface.
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Current Distribution in DC: With DC, the current density will be relatively uniform throughout the conductor's cross-sectional area, assuming the conductor is homogeneous. Any minor variations in current density in a DC circuit are typically due to variations in conductivity or temperature across the conductor, not the skin effect.
In summary, the skin effect is an AC phenomenon. Since DC has zero frequency, the skin effect is not observed.
