Thermionic emission

Thermionic emission (archaically known as the Edison effect) is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. The effect increases dramatically with increasing temperature (1000-3000 K), but is always present at temperatures above absolute zero. The science dealing with this phenomenon is thermionics. The charged particles are called thermions.

External links

• How vacuum tubes really work - Has a good section on thermionic emission, with equations
• Owen Richardson's Nobel lecture on thermionics, December 12, 1929. (PDF)
• History of the electron tube