Richardson-Dushman equation

A formula known as Richardson’s law (first proposed by the English physicist Owen W. Richardson) is roughly valid for all metals. It is usually expressed in terms of the emission current density (J) as in amperes per square metre. The Boltzmann constant k has the value

…popular models rest on the Richardson-Dushman equation, derived in the 1920s, and the Langmuir-Child equation, formulated shortly thereafter. The former states that the current per unit of area, J, is given by where k is Boltzman’s constant, A is a constant of the material and its

…emitter is given by the Richardson–Dushman equation; i.e., where T is the absolute temperature in kelvins of the emitter, e is the electronic charge in coulombs, and k is Boltzmann’s gas constant in joules per kelvin. The parameter

…called Richardson’s law or the Richardson-Dushman equation, became an important aid in electron-tube research and technology. (See also thermionic emission.) In 1914 Richardson became professor of physics and, 10 years later, director of research at King’s College of the University of London, retiring in 1944. He was knighted in 1939.