# Richardson-Dushman Theory Of Thermionic Emission

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Use the Richardson-Dushman theory of thermionic emission to determine the emission current density for a tungsten filament at a temperature of 2600K
Thermionic emission is the process by which free electrons are emitted from a metal when an external energy is applied towards the metal. When a smaller proportionate heat energy is applied to the metal, the valence electron will gain enough energy and break the bond from the parent atom. Once broken free, the free electrons in the metal may have some kinetic energy. However, there is not enough to escape the metal. The process of Thermionic emission is widely used as a source of electron in electron tubes, the heat supplies some electrons with at least the minimal energy required to overcome the attractive force holding them in structure of the metal. (Encyclopedia Britannica, 2017)
Richardson-Dushman’s equation relates to the theory of thermionic expulsion, which determines that ‘thermionic emission, discharge of an electron from heated materials.’ This theory is widely used as a source of electrons in conventional electron tubes.
Thermionic emission is a process of emission of charge particles (known as thermion) from the surface of a heated metal (Simion.com, 2017)
Js=A×T^2 e^(((-W)/kT) )
Where
“Js” is the current density of the emission (mA/mm2)
“A” is richardson’s constant. A = 4*πmek2/h3 ~ 1202 mA/mm2K2, m is the mass of electron, e is elementary charge, h is Plank's constant
“T” is temperature (K)
“W” is the work