# Thomson Effect

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Related to Thomson Effect: Seebeck effect, Peltier effect

## Thomson effect:

see thermoelectricitythermoelectricity,
direct conversion of heat into electric energy, or vice versa. The term is generally restricted to the irreversible conversion of electricity into heat described by the English physicist James P.
.

## Thomson effect

A phenomenon discovered in 1854 by William Thomson, later Lord Kelvin. He found that there occurs a reversible transverse heat flow into or out of a conductor of a particular metal, the direction depending upon whether a longitudinal electric current flows from colder to warmer metal or from warmer to colder. Any temperature gradient previously existing in the conductor is thus modified if a current is turned on. The Thomson effect does not occur in a current-carrying conductor which is initially at uniform temperature. See Thermoelectricity

## Thomson Effect

(known in English as the magnetoresistance of ferromagnetic metals), a change in the electrical resistivity of a ferromagnetic metal that occurs when the metal is magnetized by an external magnetic field. Discovered by W. Thomson (Lord Kelvin) in 1851, the Thomson effect is a manifestation of magnetoresistance, which is a galvanomagnetic phenomenon.

## Thomson Effect

a thermoelectric effect in which a quantity of heat Q, called the Thomson heat, is evolved or absorbed by a current-carrying conductor if a temperature gradient exists in the conductor. The Thomson heat is in addition to the heat evolved in accordance with Joule’s law; the direction of the current determines whether the Thomson heat is evolved or absorbed. The Thomson heat is proportional to the current I, time t, and temperature drop T2T1; that is, Q = τ(T2T1)It. The discovery of the effect was reported by W. Thomson (Lord Kelvin) in 1856. The Thomson coefficient τ depends on the nature of the material in question.

## Thomson effect

[′täm·sən i‚fekt]
(physics)
A thermoelectric effect in which heat flows into or out of a homogeneous conductor when an electric current flows between two points in the conductor at different temperatures, the direction of heat flow depending upon whether the current flows from colder to warmer metal or from warmer to colder.
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