What causes skin effect in AC currents?

In summary, skin effect in AC currents is caused by the tendency of alternating current to distribute itself unevenly within a conductor, leading to a higher current density near the surface than in the center. This phenomenon occurs due to the interaction between the magnetic fields generated by the current and the conductor itself, resulting in increased resistance at greater depths as frequency rises. Consequently, the effective cross-sectional area through which the current flows decreases, impacting the conductor's performance, especially at higher frequencies.
  • #1
Qmavam
16
3
My assumption has been it is the electromagnetic field starting from the center of the wire that pushes the electrons outward.
However, this would also be true of a DC current, but it isn't.
So why does an AC current cause electrons to move toward the skin of a wire?
I don't recall ever seeing this explained.
Thanks, Mikek
 
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  • #2
Qmavam said:
So why does an AC current cause electrons to move toward the skin of a wire?
It does not.
The current starts on the outside surface, and moves slowly into the conductor.

The incident loop of magnetic field, around the wire, causes a current to flow along the wire.
That causes an opposite magnetic field loop, that cancels most of the incident field, which reduces the magnetic field entering the conductor, and so the current stays on the surface.
 

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