Thermocouple, << THUR moh `kuhp` uhl, >> is an electric device that changes heat into electricity or electricity into heat. A thermocouple is made by joining the ends of two different kinds of wire, such as iron and copper, together to form a junction. The opposite ends are also joined to form another junction. If one junction is heated, an ammeter connected to one of the wires between the junctions will show a thermoelectric (heat-generated) current flowing. The German physicist T. J. Seebeck discovered this effect in 1821. If a battery instead of an ammeter is connected to the thermocouple, one junction will become hot and the other will become cool. This effect was first noticed by the French physicist J. C. A. Peltier in 1834.
Thermocouples are used as thermometers and to generate electricity. Some refrigeration devices use them. In a thermocouple used as a thermometer, one junction senses the temperature being measured, and the other provides the reference temperature. A voltmeter measures the voltage between the junctions and shows the temperature.
