Some important MCQ about Semiconductor Physics

 

 

 

Important Questio about Basic Electronics

 

Multiple Choice Questions.

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

1.     Covalent

2.     Electrovalent

3.     Co-ordinate

4.     None of the above

 

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

1.     Positive

2.     Zero

3.     Negative

4.     None of the above

 

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

1.     Germanium

2.     Silicon

3.     Carbon

4.     Sulphur

 

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

1.     2

2.     3

3.     6

4.     4

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

1.     6 x 10⁴ Ω cm

2.     60   Ω cm

3.     3 x 10⁶   Ω cm

4.     6 x 10^-4    Ω cm

 

 

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

1.     100 Ω cm

2.     6000 Ω cm

3.     3 x 10⁵ Ω m

4.     6 x 10^-8 Ω cm

 

 

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

1.     Goes up

2.     Goes down

3.     Remains the same

4.     Can’t say

 

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

1.     Forces between nuclei

2.     Forces between protons

3.     Electron-pair bonds

4.     None of the above

 

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

1.     An insulator

2.     An intrinsic semiconductor

3.     p-type semiconductor

4.     n-type semiconductor

 

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

1.     Free electrons

2.     Holes

3.     Valence electrons

4.     Bound electrons

 

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

1.     3

2.     5

3.     4

4.     6

 

12. An n-type semiconductor is ………

1.     Positively charged

2.     Negatively charged

3.     Electrically neutral

4.     None of the above

 

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

1.     Holes

2.     Free electrons

3.     Valence electrons

4.     Bound electrons

 

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

1.     A free electron

2.     The incomplete part of an electron pair bond

3.     A free proton

4.     A free neutron

 

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

1.     10 atoms for 10⁸ atoms

2.     1 atom for 10⁸ atoms

3.     1 atom for 10⁴ atoms

4.     1 atom for 100 atoms

 

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

1.     Remains the same

2.     Increases

3.     Decreases

4.     None of the above

 

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

1.     Repel each other

2.     Attract each other

3.     Have no effect on each other

4.     None of the above

 

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

1.     Only holes

2.     Only free electrons

3.     Holes and free electrons

4.     None of the above

 

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

1.     Diffusion

2.     Pressure

3.     Ionisation

4.     None of the above

 

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

3.     5 V

4.     3 V

5.     Zero

6.     3 V

 

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

1.     Acceptor ions

2.     Holes and electrons

3.     Donor ions

4.     None of the above

 

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

1.     Very narrow depletion layer

2.     Almost no current

3.     Very low resistance

4.     Large current flow

 

23.A pn junction acts as a ……….

1.     Controlled switch

2.     Bidirectional switch

3.     Unidirectional switch

4.     None of the above

 

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

1.     Ω

2.     kΩ

3.     MΩ

4.     None of the above

 

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

1.     Minority carriers

2.     Majority carriers

3.     Junction capacitance

4.     None of the above

 

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

1.     Junction capacitance

2.     Minority carriers

3.     Majority carriers

4.     None of the above

 

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

1.     Decreases

2.     Increases

3.     Remains the same

4.     None of the above

 

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

1.     Aa

2.     mA

3.     kA

4.     µA

 

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

1.     Equals the number of holes

2.     Is greater than the number of holes

3.     Is less than the number of holes

4.     None of the above

 

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

1.     Many holes only

2.     A few free electrons and holes

3.     Many free electrons only

4.     No holes or free electrons

 

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

1.     A few free electrons

2.     Many holes

3.     Many free electrons

4.     No holes or free electrons

 

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

1.     A battery

2.     A conductor

3.     An insulator

4.     A piece of copper wire

 

33. Under normal conditions a diode conducts current when it is ……………

1.     reverse biased

2.     forward biased

3.     avalanched

4.     saturated

 

34. The term bias in electronics usually means ……….

1.     the value of ac voltage in the signal.

2.     the condition of current through a pn junction.

3.     the value of dc voltages for the device to operate properly.

4.     the status of the diode.

 

 

 

 

Answer:

Basic Electrical Engineering Set  01

 

 

 

 

 

 

 

 

 

 

 

 

1.       1

2.       3

3.       2

4.       4

5.       2

6.       2

7.       2

8.       3

9.       4

10.   1

11.   5

12.   3

13.   1

14.   2

15.   2

16.   3

17.   2

18.   3

19.   1

20.   4

21.   2

22.   2

23.   3

24.   3

25.    1

26.    2

27.    1

28.   4

29.   1

30.   2

31.   4

32.   3

33.   2

34.   3