ELECTRICAL ENGINEERING IMPORTANT MCQ-SEMICONDUCTOR DIODE

1. A
crystal diode has ………

1.one pn junction
2.two pn junctions
3.three pn junctions
4.none of the above
ANS: 1

2. A crystal diode has forward resistance of the order of ……………

1.kΩ
2.Ω
3.MΩ
4.none of the above
ANS: 2

3. If the arrow of crystal diode symbol is positive w.r.t. bar, then
diode is ………….. biased.

1.forward
2.reverse
3.either forward or reverse
4.none of the above
ANS: 1

4. The reverse current in a diode is of the order of ……………….

1.kA
2.mA
3.μA
4.A
ANS: 3

5. The forward voltage drop across a silicon diode is about …………………

1.2.5 V
2.3 V
3.10 V
4.0.7 V
ANS: 4

6. A crystal diode is used as ……………

1.an amplifier
2.a rectifier
3.an oscillator
4.a voltage regulator
ANS: 2

7. The d.c. resistance of a crystal diode is ………….. its a.c.
resistance

1.the same as
2.more than
3.less than
4.none of the above
ANS: 3

8. An ideal crystal diode is one which behaves as a perfect ………..
when forward biased.

1.conductor
2.insulator
3.resistance material
4.none of the above
ANS: 1

9. The ratio of reverse resistance and forward resistance of a
germanium crystal diode is about ………….

1.1 : 1
2.100 : 1
3.1000 : 1
4.40,000 : 1
ANS: 4

10. The leakage current in a crystal diode is due to …………….

1.minority carriers
2.majority carriers
3.junction capacitance
4.none of the above
ANS: 1

11. If the temperature of a crystal diode increases, then leakage
current ………..

1.remains the same
2.decreases
3.increases
4.becomes zero
ANS: 3

12. The PIV rating of a crystal diode is ………….. that of equivalent
vacuum diode

1.the same as
2.lower than
3.more than
4.none of the above
ANS: 2

13. If the doping level of a crystal diode is increased, the
breakdown voltage………….

1.remains the same
2.is increased
3.is decreased
4.none of the above
ANS: 3

14. The knee voltage of a crystal diode is approximately equal to
………….

1.applied voltage
2.breakdown voltage
3.forward voltage
4.barrier potential
ANS: 4

15. When the graph between current through and voltage across a
device is a straight line, the device is referred to as ……………….

1.linear
2.active
3.nonlinear
4.passive
ANS: 1

16. When the crystal current diode current is large, the bias is
…………

1.forward
2.inverse
3.poor
4.reverse
ANS: 1

17. A crystal diode is a …………… device

1.non-linear
2.bilateral
3.linear
4.none of the above
ANS: 1

18. A crystal diode utilises …………….. characteristic for
rectification

1.reverse
2.forward
3.forward or reverse
4..none of the above
ANS: 2

19. When a crystal diode is used as a rectifier, the most important
consideration is ………..

1.forward characteristic
2.doping level
3.reverse characteristic
4.PIC rating
ANS: 4

20. If the doping level in a crystal diode is increased, the width
of depletion layer………..

1.remains the same
2.is decreased
3.in increased
4.none of the above
ANS: 3

21. A zener diode has ………..

1.one pn junction
2.two pn junctions
3.three pn junctions
4.none of the above
ANS: 1

22. A zener diode is used as …………….

1.an amplifier
2.a voltage regulator
3.a rectifier
4.a multivibrator
ANS: 2

23. The doping level in a zener diode is …………… that of a crystal
diode

1.the same as
2.less than
3.more than
4.none of the above
ANS: 3

24. A zener diode is always ………… connected.

1.reverse
2.forward
3.either reverse or forward
4.none of the above
ANS: 1

25. A zener diode utilizes ……….. characteristics for its operation.

1.forward
2.reverse
3.both forward and reverse
4.none of the above
ANS: 2

26. In the breakdown region, a zener didoe behaves like a ……………
source.

1.constant voltage
2.constant current
3.constant resistance
4.none of the above
ANS: 1

27. A zener diode is destroyed if it…………..

1.is forward biased
2.is reverse biased
4.none of the above
ANS: 3

28. A series resistance is connected in the zener circuit to………..

1.properly reverse bias the zener
2.protect the zener
3.properly forward bias the zener
4.none of the above
ANS: 2

29. A zener diode is …………………. device

1.a non-linear
2.a linear
3.an amplifying
4.none of the above
ANS: 1

30. A zener diode has ………….. breakdown voltage

1.undefined
2.sharp
3.zero
4.none of the above
ANS: 2

31. ……………. rectifier has the lowest forward resistance

1.solid state
2.vacuum tube
3.gas tube
4.none of the above
ANS: 1

32. Mains a.c. power is converrted into d.c. power for ……………..

1.lighting purposes
2.heaters
3.using in electronic equipment
4.none of the above
ANS: 3

33. The disadvantage of a half-wave rectifier is that the……………….

1.components are expensive
2.diodes must have a higher power rating
3.output is difficult to filter
4.none of the above
ANS: 3

34. If the a.c. input to a half-wave rectifier is an r.m.s value of
400/√2 volts, then diode PIV rating is ………………….

1.400/√2 V
2.400 V
3.400 x √2 V
4.none of the above
ANS: 2

35. The ripple factor of a half-wave rectifier is …………………

1.2
2.1.21
3.2.5
4.0.48
ANS: 4

36. There is a need of transformer for ………………..

1.half-wave rectifier
2.centre-tap full-wave rectifier
3.bridge full-wave rectifier
4.none of the above
ANS: 2

37. The PIV rating of each diode in a bridge rectifier is ………………
that of the equivalent centre-tap rectifier

1.one-half
2.the same as
3.twice
4.four times
ANS: 1

38. For the same secondary voltage, the output voltage from a
centre-tap rectifier is ………… than that of bridge rectifier

1.twice
2.thrice
3.four time
4.one-half
ANS: 4

39. If the PIV rating of a diode is exceeded, ………………

1.the diode conducts poorly
2.the diode is destroyed
3.the diode behaves like a zener diode
4.none of the above
ANS: 2

40. A 10 V power supply would use …………………. as filter capacitor.

1.paper capacitor
2.mica capacitor
3.electrolytic capacitor
4.air capacitor
ANS: 3

41. A 1,000 V power supply would use ……….. as a filter capacitor

1.paper capacitor
2.air capacitor
3.mica capacitor
4.electrolytic capacitor
ANS: 1

42. The ……………….. filter circuit results in the best voltage
regulation

1.choke input
2.capacitor input
3.resistance input
4.none of the above
ANS: 1

43. A half-wave rectifier has an input voltage of 240 V r.m.s. If
the step-down transformer has a turns ratio of 8:1, what is the peak load
voltage? Ignore diode drop.

1.27.5 V
2.86.5 V
3.30 V
4.42.5 V
ANS: 4

44. The maximum efficiency of a half-wave rectifier is ………………..

1.40.6 %
2.81.2 %
3.50 %
4.25 %
ANS: 1

45. The most widely used rectifier is ……………….

1.half-wave rectifier
2.centre-tap full-wave rectifier
3.bridge full-wave rectifier
4.none of the above
ANS: 3
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