What does the skin effect refer to in AC current flow?

The skin effect describes a phenomenon in alternating current (AC) where the current density is highest near the surface of the conductor and decreases exponentially with depth into the conductor. This occurs due to the alternating nature of AC, which generates magnetic fields that influence how the current distributes itself in a conductor. As the frequency of the current increases, the skin effect becomes more pronounced, leading to a greater concentration of current towards the outer layer of the conductor.

Understanding the skin effect is crucial for electrical design and engineering, as it affects the effective resistance and inductance of conductors at high frequencies. This is why the correct answer identifies the concentration of flow near the surface of a conductor, contrasting with options that describe uniform flow, temperature effects, or general resistance, which do not accurately characterize the behavior of AC in conductors.