Skin effect
= Skin effect
{wiki}
An alternating <electric current> and its <electromagnetic field> concentrate near a conductor's surface. For a local isotropic good conductor with real <electrical conductivity> $\sigma$, magnetic permeability $\mu$, and $\sigma\gg\omega\epsilon$, the field penetrates over the <skin depth> $\delta=\sqrt{2/(\mu\sigma\omega)}$.