Skin effect

Skin effect is the tendency of alternating current to concentrate near a conductor’s surface as frequency increases, reducing the effective area available for conduction.

Electromagnetic induction: The production of an electromotive force by a changing magnetic flux. Current-generated magnetic fields induce opposing electric fields inside the conductor.
Alternating current: Electric current that periodically reverses direction. Its changing direction and frequency produce the fields responsible for skin effect.
Direct current: Electric current that flows in one direction without periodically reversing. Steady direct current does not exhibit frequency-driven surface concentration.
Electrical conductivity: A measure of how readily a material carries electric current. Conductivity enters directly into the classical skin-depth relation.
Magnetic diffusion: The gradual penetration and spreading of magnetic fields through a conducting material. Its diffusion equation predicts how deeply alternating fields penetrate a conductor.
Proximity effect: The redistribution of alternating current in a conductor caused by magnetic fields from nearby conductors. It combines with skin effect to increase AC resistance in closely spaced wires.
Electrical resistance: The opposition a material offers to electric current. Skin effect is one reason a conductor’s AC resistance exceeds its DC resistance.
Magnetic permeability: A measure of how a material responds to an applied magnetic field. Higher permeability generally reduces skin depth at a given frequency.
Skin depth: The depth at which an alternating electromagnetic field’s amplitude falls to about 1/e of its surface value. It quantifies the depth over which current substantially penetrates.
Litz wire: A cable made from many individually insulated, transposed strands to reduce high-frequency AC losses. Its strand geometry limits current crowding at frequencies where solid wire loses efficiency.

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