Multiple choice

On which of the following factors does the rate of emission of electrons depend?

  1. Surface area of filament

  2. Temperature of filament

  3. Material used for filament

  4. Surface area and temperature of filament, and the material used for filament
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D Correct answer
Explanation

Thermionic emission is the emission of electrons from a heated filament or substance. When a filament like tungsten is heated to a high temperature, some electrons acquire sufficient energy and are able to break away from the surface of material and go into space. So, rate of emission of electrons depends upon surface area and temperature of filament and also on the material used for filament.

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