300+ TOP Semiconductor Theory MCQ Questions and Answers

SEMICONDUCTOR THEORY Questions :-

1. A semiconductor is formed by ……… bonds.

A. Covalent
B. Electrovalent
C. Co-ordinate
D. None of the above
Answer: A

2. A semiconductor has ………… temperature coefficient of resistance.

A. Positive
B. Zero
C. Negative
D. None of the above
Answer: C

3. The most commonly used semiconductor is ………..

A. Germanium
B. Silicon
C. Carbon
D. Sulphur
Answer: B

4. A semiconductor has generally ……………… valence electrons.

A. 2
B. 3
C. 6
D. 4
Answer: D

5. The resistivity of pure germanium under standard conditions is about ……….

A. 6 x 104
B. O cm
C. 60
D. O cm
Answer: B

6. The resistivity of a pure silicon is about ……………

A. 100 O cm
B. 6000 O cm
C. 3 x 105 O m
D. 6 x 10-8 O cm
Answer: B

7. When a pure semiconductor is heated, its resistance …………..

A. Goes up
B. Goes down
C. Remains the same
D. Can’t say
Answer: B

8. The strength of a semiconductor crystal comes from ……..

A. Forces between nuclei
B. Forces between protons
C. Electron-pair bonds
D. None of the above
Answer: C

9. When a pentavalent impurity is added to a pure semiconductor, it becomes ………

A. An insulator
B. An intrinsic semiconductor
C. p-type semiconductor
D. n-type semiconductor
Answer: D

10. Addition of pentavalent impurity to a semiconductor creates many ……..

A. Free electrons
B. Holes
C. Valence electrons
D. Bound electrons
Answer: A

11. A pentavalent impurity has ………. Valence electrons

3
5
4
6
Answer: B

12. An n-type semiconductor is ………

Positively charged
Negatively charged
Electrically neutral
None of the above
Answer: C

13. A trivalent impurity has ….. valence electrons

4
5
6
3
Answer: D

14. Addition of trivalent impurity to a semiconductor creates many ……..

Holes
Free electrons
Valence electrons
Bound electrons
Answer: A

15. A hole in a semiconductor is defined as …………….

A free electron
The incomplete part of an electron pair bond
A free proton
A free neutron
Answer: B

16. The impurity level in an extrinsic semiconductor is about ….. of pure semiconductor.

10 atoms for 108 atoms
1 atom for 108 atoms
1 atom for 104 atoms
1 atom for 100 atoms
Answer: B

17. As the doping to a pure semiconductor increases, the bulk resistance of the semiconductor ………..

Remains the same
Increases
Decreases
None of the above
Answer: C

18. A hole and electron in close proximity would tend to ……….

Repel each other
Attract each other
Have no effect on each other
None of the above
Answer: B

19. In a semiconductor, current conduction is due to ……..

Only holes
Only free electrons
Holes and free electrons
None of the above
Answer: C

20. The random motion of holes and free electrons due to thermal agitation is called ……….

Diffusion
Pressure
Ionisation
None of the above
Answer: A

21. A forward biased pn junction diode has a resistance of the order of

O
kO
MO
None of the above
Answer: A

22. The battery connections required to forward bias a pn junction are ……

+ve terminal to p and –ve terminal to n
-ve terminal to p and +ve terminal to n
-ve terminal to p and –ve terminal to n
None of the above
Answer: A

23. The barrier voltage at a pn junction for germanium is about ………

5 V
3 V
Zero
3 V
Answer: D

24. In the depletion region of a pn junction, there is a shortage of ……..

Acceptor ions
Holes and electrons
Donor ions
None of the above
Answer: B

25. A reverse bias pn junction has …………

Very narrow depletion layer
Almost no current
Very low resistance
Large current flow
Answer: B

26. A pn junction acts as a ……….

Controlled switch
Bidirectional switch
Unidirectional switch
None of the above
Answer: C

27. A reverse biased pn junction has resistance of the order of

O
kO
MO
None of the above
Answer: C

28. The leakage current across a pn junction is due to …………..

Minority carriers
Majority carriers
Junction capacitance
None of the above
Answer: A

29. When the temperature of an extrinsic semiconductor is increased, the pronounced effect is on……

Junction capacitance
Minority carriers
Majority carriers
None of the above
Answer: B

30. With forward bias to a pn junction , the width of depletion layer ………

Decreases
Increases
Remains the same
None of the above
Answer: A

31. The leakage current in a pn junction is of the order of

Aa
mA
kA
µA
Answer: D

32. In an intrinsic semiconductor, the number of free electrons ………

Equals the number of holes
Is greater than the number of holes
Is less than the number of holes
None of the above
Answer: A

33. At room temperature, an intrinsic semiconductor has ……….

Many holes only
A few free electrons and holes
Many free electrons only
No holes or free electrons
Answer: B

34. At absolute temperature, an intrinsic semiconductor has ……….

A few free electrons
Many holes
Many free electrons
No holes or free electrons
Answer: D

35. At room temperature, an intrinsic silicon crystal acts approximately as ……

A battery
A conductor
An insulator
A piece of copper wire
Answer: B

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