What is the phenomenon called that describes the increased concentration of AC current near the surface of a conductor?

The phenomenon that describes the increased concentration of AC current near the surface of a conductor is known as the Skin Effect. This occurs because alternating current (AC) generates a changing magnetic field, which induces eddy currents in the conductor. These eddy currents flow in a direction opposite to the applied current, causing the current density to be higher near the surface and lower at greater depths within the conductor. As a result, the effective resistance increases and less current flows through the center. This phenomenon is especially pronounced at higher frequencies, which is important for understanding how AC signals behave in various applications such as electrical wiring, transformers, and radio frequency circuits.

The other terms, while related to electrical concepts, do not accurately describe this phenomenon. Eddy currents refer to circulating currents induced within conductors when exposed to changing magnetic fields, but they are not synonymous with the concentration of current near the surface. The relay effect is not a standard term used in this context, and magnetic flux describes the measure of the magnetic field over a given area rather than the distribution of current within a conductor.