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The Seebeck effect, discovered in 1821 by Thomas Johann Seebeck, converts temperature differences between two dissimilar metals in a circuit into an electric current. The Peltier effect and Thomson effect are related phenomena. Thermocouple thermometers use these effects to convert thermal potential difference into electrical potential difference.
The Seebeck effect describes a thermoelectric phenomenon by which temperature differences between two dissimilar metals in a circuit are converted into an electric current.
Discovered in 1821, the Seebeck effect is one of three reversible phenomena describing similar processes related to thermoelectricity, conductivity and temperature. The Peltier effect was first observed in 1834 and the Thomson effect was first explained in 1851.
The Seebeck effect is named after the East Prussian scientist Thomas Johann Seebeck (1770-1831). In 1821, Seebeck discovered that a circuit composed of two dissimilar metals conducts electricity if the two points where the metals connect are kept at different temperatures. Seebeck placed a compass near the circuit he built and noticed that the needle deflected. He found that the amount of deflection increased as the temperature difference increased. His experiments also noted that the temperature distribution along the metal conductors did not affect the compass. However, by changing the types of metals he used he changed the amount the needle deflected.
The Seebeck coefficient is a number describing the voltage produced between two points on a conductor, where there is a uniform temperature difference of 1 kelvin between the points. The metals in Seebeck’s experiments reacted to temperatures, creating a current loop in the loop and a magnetic field. Unaware of an electric current at the time, Seebeck incorrectly assumed it was a thermomagnetic effect.
In 1834, the French scientist Jean Charles Athanase Peltier (1784-1845) described the second closely related phenomenon, now known as the Peltier effect. In his experiment, Peltier changed the voltage between the metal conductors and found that the temperature at both junctions changed proportionally. In 1839, the German scientist Heinrich Lenz (1804-1865) furthered Peltier’s discovery and described the heat transfer at junctions, depending on the direction in which current flows along the circuit. While these two experiments focused on different parts of the circuit and thermoelectric effects, they are often referred to simply as the Seebeck-Peltier effect or Peltier-Seebeck effect.
In 1851, British physicist William Thomson (1824-1907), later known as 1st Baron Kelvin, observed the heating or cooling of a single type of metal conductor by an electric current. The Thomson effect describes the rate of heat created or absorbed in a current-carrying metal or other conductive material, subject to a temperature gradient.
Thermocouple thermometers are electrical engineering instruments based on the measurement of the Seebeck effect and Peltier and Thompson effects. Thermometers work by converting thermal potential difference into electrical potential difference.
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