Kelvin, William Thomson, 1st Baron definition of Kelvin, William Thomson, 1st Baron in the Free Online Encyclopedia.

Kelvin, William Thomson, 1st Baron, 1824–1907, British mathematician and physicist, b. Belfast. He was professor of natural philosophy at the Univ. of Glasgow (1846–99). He is known especially for his work on heat and electricity. In thermodynamics Carnot cycle after the French physicist Sadi Carnot , who first discussed the implications of such cycles. During the Carnot cycle occurring in the operation of a heat engine, a definite quantity of heat is absorbed from a reservoir at high temperature; part of this heat is
..... Click the link for more information. his work of coordinating the theories of heat held by various leading scientists of his time established firmly the law of the conservation of energy as proposed by Joule. He introduced the Kelvin temperature scale Kelvin temperature scale, a temperature scale having an absolute zero below which temperatures do not exist. Absolute zero , or 0°K;, is the temperature at which molecular energy is a minimum, and it corresponds to a temperature of −273.
..... Click the link for more information. , or absolute scale, of temperature temperature, measure of the relative warmth or coolness of an object. Temperature is measured by means of a thermometer or other instrument having a scale calibrated in units called degrees. The size of a degree depends on the particular temperature scale being used.
..... Click the link for more information. . He also discovered the Thomson effect in thermoelectricity thermoelectricity, 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.
..... Click the link for more information. . The importance of the discoveries and improvements that he made in connection with the transmission of messages by submarine cables led to his establishment as a leading authority in this field. He invented the reflecting galvanometer and the siphon recorder, an instrument by which telegraphic messages are recorded in ink fed from a siphon.

His brother,

James Thomson, 1822–92, an engineer, was professor at Queen's College, Belfast, from 1857 to 1873. He is known for his studies of the variation in melting point with pressure as well as for his research in hydraulics.

Bibliography

See biographies of Baron Kelvin by S. P. Thompson (1910) and A. G. King (1925).