Question

Why hotter filament is used in cathode ray tube ?

• A. To reduce rate of electron emission
  
• B. To increases rate of electron emission
• C. To increases energy emission
  
• D. To decrease energy emission
  

Answer 1

The correct option is B To increases rate of electron emission

Thermal energy given to the charge carriers overcome the work function of the metal surface and thus flow of charge carriers (electrons) takes place from the metal surface. More the thermal energy given to the metal surface by increasing its temperature, more easily the charge carriers overcome the work function and thus more will be the rate of emission of charge carriers. Hence hotter filament is used in cathode ray tube to increase the rate of electron emission.