Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectric Current through Gases

If the plate current in a diode is found to be zero, it is possible that

Options

Athe plate voltage is highly positive and the filament is highly heated
Bthe temperature of the filament is low
Cthe plate voltage is zero
Dthe plate voltage is slightly negative

Correct answer

D. the plate voltage is slightly negative

Step-by-step solution

The plate current in a vacuum diode is zero when no electrons reach the anode (plate). This can occur due to the following reasons: If the temperature of the filament is low, thermionic emission does not occur, meaning no electrons are emitted from the cathode. If the plate voltage is zero, there is no accelerating electric field to attract the electrons towards the plate. In an ideal diode, this results in zero plate current. If the plate voltage is slightly negative, it acts as a retarding potential. This repels

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