Eddy currents are currents that are generated in a conductor to produce magnetic fields that oppose the magnetic field originally produced by current flowing in the conductor. The figure below (from Wikipedia's skin effect article) depicts this nicely:
Current $I$ flows up through a wire, producing a counterclockwise magnetic field $H$ into and out of the page. By Lenz's law, to oppose this change in flux, an eddy current $I_W$ is created that flows in concentric circles centered along $H$ which produces a magnetic field that opposes $H$. This is known as the skin effect.
- Is the skin effect worse for alternating currents (AC) than for direct currents (DC) since for DC, the change in magnetic flux goes to zero after the initial transient period when current $I$ starts to flow?
- When the eddy currents are flowing, is the magnetic field inside the conductor zero?
- If the answer to 2 is no, then are eddy currents linear? I.e. for a given location $(r, \theta, z)$ inside the conductor, does doubling the current result in a doubling of the magnetic field? Or does the presence of eddy currents diminish / enhance the magnetic field in a nonlinear way?