James Prescott Joule
(1818 - 1889)

born: December 24, 1818 in Salford near Manchester died: October 11, 1989 in Sale near London British physicist. Was a brewer in Salford and is often considered as the founder of experimental thermodynamics. Formulated in 1840 that the heat (Q) produced in an electric wire in the time dt is Q = U I dt. This is known as Joules Law. In 1843 he determined the mechanical equivalent of heat (See also J.R. Mayer and S. Carnot) and formulated the law of conservation of energy. (The same Law was formulated by J.R. Mayer in 1842 and by L. Helmholtz in 1847.) Together with W. Thomson (Lord Kelvin) he discovered 1853 the effect known as Joule-Thomson effect. The SI Unit "Joule" was named in his honour.