Draw and label the symbol of the following valves:
directly heated cathode triode;
indirectly heated cathode pentode.
The expected answers were:
Secondary emission is the process in which electrons (in motion) striking an electrode give that kinetic energy to the electrode such that other electrons are emitted by the impact.
The question was on Electron Emission and Thermionic Devices. It was quite unpopular with the candidates. On average, the performance was low mainly because many candidates appeared to be unfamiliar with the triode parameters.
