Electronics Engineering Question:

In a conducting material, the electrons are governed by Fermi-Dirac statistics. The baseline electron energy is the Fermi Energy*, and at low temperatures the electrons all exist at or below this level. As temperature is increased, so the distribution function for the electrons develops a high energy 'tail'. Some of these electrons have sufficient energy to pass over the surface potential barrier between the material and the vacuum. This process of increasing the temperature of a bulk material to increase the number of electrons which can leave the material is called thermionic emission or Edison effect.