Question

State the characteristics required for a good thermionic emitter.

Answer 1

The characteristics required for a good thermionic emitter are:

(i) The work function (mimimum amount of energy required to emit electrons) of the substance should be low so that electrons may be emitted from it even when it is not heated to a very high temperature.
(ii) The melting point of the substance should be high so that it may not melt when heated to the required temperature to emit electrons.