Electrical induction heating is a complex combination of electromagnetic, heat transfer and metallurgical phenomena.
- The electromagnetic phenomena occur when a rapidly alternating current is applied to an induction coil.
- The alternating voltage results in an alternating current source in the coil.
- The alternating source current produces a time variable magnetic field within its immediate surroundings of the same frequency as the source current.
- The magnetic field induces eddy currents in its surrounding electrical conducting metal objects. The induced eddy currents have the same frequency but different direction from the source current.
- The induced currents produce Joule heating (I²R) in the surrounding metal objects.
Alternating current in a conductor has a non-uniform current distribution with the maximum on the surface. The non-uniform current distribution with alternating current is known as the skin effect. Approximately 86% of the power is concentrated in the surface layer of the conductor. The surface layer is called the penetration or skin depth, 
, and can be derived from the Maxwell equations
- f is the frequency is Hertz (Hz). Typical frequency ranges for induction heating are 5kHz to 100 kHz.
is the magnetic permeability of the material 
is the electrical conductivity of the material, or its ability to conduct electrical current. Good electrical conductors, such as copper, have high conductivity, or low resistivity. Don't confuse electrical resistivity with electrical resistance. Electrical resistivity is an imperative physical property of a material, that influences induction heating by affecting the depth of heating, uniformity of heating, coil electrical efficiency and coil impedence.
You can see from this equation that the skin depth depends on the conductor properties and the frequency of the current in the conductor. When it comes to a simulation, the skin depth should also be considered when selecting the size of the mesh.