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  1. What is thermionic emission?

  2. What types of material are used in plate of a valve diode?

  3. Why is the plate coated?

  4. Why is the indirectly heated cathode used more than the directly heated ones?

  5. The inside of a vacuum tube diode is evacuated, why?

  6. Is it necessary to keep grid inside the triode?

  7. How will you distinguish between the static and dynamic characteristics of a triode?

  8. What happens when grid voltage is increased in the triode valve?

  9. Why small current flow in the triode valve even after source voltage is removed?

  10. Triode valve is not used in all grid voltages, which one region is of best use?

  11. What is valve diode?

  12. What is valve triode?

  13. Why grid is kept at negative potential?

  14. What differentiates static and mutual characteristics of a value triode?

  15. What is the action of diode valve?

  16. What is meant by semiconductor?

  17. What are the differences between a conductor, semiconductor and an insulator?

  18. What will happen to the number of electrons in the conduction band of a semiconductor as the temperature of the material is increased?

  19. Explain the reason why the conductivity of germanium is more than that of silicon at room temperature

  20. Explain why the temperature coefficient of resistance of a semiconductor is negative.



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