class 12 CBSE PHYSICS SEMICONDUCTOR DEVICES

 QUESTIONS/SUMS BASED ON IMPORTANT CONCEPTS


1. Define Electronic device. State its two basic types.

2. Classify solids on the basis of their values of electrical conductivity and resistivity.

3. Classify semiconductors on the basis of their chemical composition. Give some examples of each.

4. Classify semiconductors on the basis of the source and the nature of the charge carriers.

5. Describe the mechanism of conduction in intrinsic semiconductors on the basis of valence bond model.

6. How do holes act as positive charge carriers?

7. Mention the limitations of intrinsic semiconductors.

8. What is doping?

9. What are the requisites of doping?

10. Mention the two types of dopants.

11. Mention the various methods of doping.

12.  Mention the two types of extrinsic semiconductors.

13. Define
1. Valence band
2. Conduction band
3. Energy band

14. Distinguish between intrinsic and extrinsic semiconductors .

15. Distinguish between n-type and p-type semiconductors.

16. Write the characteristics of holes.

17. A semiconductor has equal electron and hole concentration of 2 x 10⁸ m⁻³.  On doping with a certain impurity, the hole concentration increases to 4  x 10¹⁰ m⁻³.

(i) what type of semiconductor is obtained on doping?

(ii) find the new electron concentration of the semiconductor.

(iii) how does the energy gap vary with doping?

18. Define electrical mobility of a charge carrier  Why is the mobility of an electron in the conduction band of a semiconductor is more than the mobility of a hole (or electron) in the valence band?

19. Explain the variation of conductivity of a semiconductor with temperature.

20 What is p-n junction?

21 What is depletion region in p-n junction?

22. Explain the two important processes involved in the formation of p-n junction. 

23. Explain with necessary diagrams forward and reverse biasing of a p-n junction diode.

24. Explain half wave rectifier with the help of a circuit diagram . Draw the input /output graphs 

25. Explain full wave rectifier with the help of a circuit diagram. Draw the input/output graphs.

26. Sketch the V-I characteristics of a junction diode (Forward, reverse and complete).

27. Define reverse or leakage current.

28. Define barrier potential. State the factors on which barrier potential depends.

29. Write the value of barrier potential for Silicon and Germanium.



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