Monday, 31 October 2016

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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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