What is Skin Effect?

When a DC current is applied to a cylindrical conductor, it gets distributed uniformly over the entire cross section of the conductor. In the case of non-cylindrical conductor, current is not uniformly distributed but it exists in the entire conductor.

On the other hand, when an AC current is applied to a cylindrical conductor, the current concentrates near the surface of the conductor and its strength decreases as you go towards the center of the conductor.

The depth of the AC current in a conductor is inversely proportional to the frequency i.e  at lower frequencies the current goes deeper in to the conductor whereas at higher frequencies the current flows almost on the surface of the conductor. This entire phenomenon is called as Skin Effect.

The depth till which conduction takes place in a conductor or the depth till which the current flows in a conductor is called as Skin Depth.