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
(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.
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 T2 – T1; that is, Q = τ(T2 –T1)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.