Induction heating is the process of heating a material through the generation of eddy current. An external applied alternating magnetic field is applied, and heat is generated from the resistance to the eddy current (i.e., Joule heating). Eddy current is the main heat source; however, heat may also be generated in magnetic materials from alternating magnetization and hysteresis. The induced current is commonly called eddy current, although it is also known as Foucault current after its discoverer, Jean Bernard Léon Foucault (1819–1868). We will, in the following text, use the notation eddy current. In general, the eddy current distribution inside the work piece is not uniform. The magnitude of the eddy current attenuates exponentially beneath the surface, which implies that the current density near the surface is greater than at a depth. The surface of a material will therefore be heated faster than the interior. This phenomenon is referred to as the skin effect.