Thermoelectric effect

Thermoelectricity, electricity produced directly from heat. The production of electricity from heat is called the Seebeck effect, after the German physicist Thomas J. Seebeck, who discovered the phenomenon in the 1820's. Thermoelectricity arises in an electric circuit in which two dissimilar conductors or semiconductors are joined at their ends. When one of the junctions is at a different temperature than the other, a direct electric current will flow in the circuit. For a given thermoelectric circuit operating in a given temperature range, the magnitude of the current depends mainly on the temperature difference between the two junction.

An explanation of the Seebeck effect requires an understanding of the behavior of electrons inside a metal. Not all the electrons inside a metal are bound to specific atoms; some are free to move about. These free electrons behave like a gas. The density of the 'free' electrons differs from metal to metal.