Thermionic emission

Thermionic emission is the process by which electrons are released from a metal surface when it is heated. At high temperatures, atoms in the metal gain enough energy to allow some electrons to overcome the attractive forces holding them, freeing them to flow as an electric current. This phenomenon is used in devices like vacuum tubes and electron guns, where controlled electron flow is essential. Essentially, heating gives electrons enough energy to escape from the metal's surface, enabling electrical conduction through electron emission.