Method of raising the temperature of an electrically conductive material by subjecting it to an alternating electromagnetic field .
Energy in the electric currents induced in the object is dissipated as heat . Induction heating is used in metalworking to heat metals for soldering, tempering, and annealing, and in induction furnaces for melting and processing metals. The principle of the induction-heating process resembles that of the transformer. A water-cooled coil (inductor), acting as the primary winding of a transformer, surrounds the material to be heated (the workpiece), which acts as the secondary winding. Alternating current flowing in the primary coil induces eddy currents in the workpiece, causing it to become heated. The depth to which the eddy currents penetrate, and therefore the distribution of heat within the object, depend on the frequency of the primary alternating current and the magnetic permeability, as well as the resistivity, of the material.