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

As a result of the space charge in a diode valve,

Options

Athe emission rate of thermions increases
Bthe saturation current increases
Cthe plate current decreases
Dthe plate voltage increases

Correct answer

C. the plate current decreases

Step-by-step solution

In a diode valve, the space charge is the accumulation of emitted electrons in the region between the cathode and the anode. Since electrons are negatively charged, this electron cloud exerts a repulsive force on the newly emitted thermions from the cathode. Due to this repulsion, some of the emitted electrons are pushed back towards the cathode and are unable to reach the anode. Consequently, the net flow of electrons to the plate is reduced, which means the plate current decreases.

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