Question

Thermionic emitters can be classified into _________ and ________ .

• A. direct LED and indirect LED
• B. direct transistor and indirect transistor
• C. directly heated thermionic emitter and indirectly heated thermionic emitter
• D. directly heated emitter and indirectly heated emitter

Answer 1

The correct option is C directly heated thermionic emitter and indirectly heated thermionic emitter

Thermionic emission is the process on which heat energy is applies externally to the metal surface, from where the electrons are emitted.

The substance from which electrons are emitted is known as emitter or cathode. With regard to thermionic emission there are two types of cathode.

a. In-direct heated cathode: In this type of cathode, heater current does not flow through cathode, but through heater element that is known as filament.

b.Direct heated cathode: In this type of cathode both heater current and emitter electrons come from it.