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Seebeck, Thomas Johann

effect current emf junctions

[ zay bek] (1770–1831) Estonian–German physicist: discovered the thermoelectric effect.

A member of a wealthy merchant family, Seebeck went to Germany to study medicine. He qualified in 1802 but thereafter spent his time in research in physics. His best-known work was done in Berlin in 1822, when he showed that, if a circuit is made of a loop of two metals with two junctions, then when the junctions are at different temperatures a current flows (eg if copper and iron are used and the junctions are at 0°C and 100°C, the circuit has an EMF of about a millivolt). Seebeck himself did not grasp that a current was generated (he saw only that a nearby compass needle was affected) and called the effect ‘thermomagnetism’. Later it was realized that whenever two different metals are in contact, an EMF is set up. whose magnitude depends on the temperature (the thermoelectric or Seebeck effect). The effect is used in the thermocouple for temperature measurement.

In 1834 the watchmaker J C A Peltier (1785–1845) found the converse effect: when a current is passed through a junction of two different conductors, a thermal effect occurs (heating or cooling, depending on the direction of the current, ie whether the current adds to or opposes the EMF of the junction). The related effect is the development of an EMF between the ends of a single metal rod when these ends are at different temperatures. These two effects are mainly of theoretical interest.

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