A thermoelectric cell produces an electric current directly from heat through differences in temperature. A simple thermoelectric cell consists of two conductors made of different kinds of metal, joined together in two places (the junctions). One of the junctions is then heated (or cooled) with respect to the other. As the temperatures at the two junctions begin to differ, a current starts to flow through the circuit. The strength of the current depends on the kinds of metals used as conductors, and on how great a difference there is in the temperatures of the two junctions.