Diode - Electrical Engineering (MCQ) questions and answers

1. The diode has

A. 4 pn junctions
B. 3 pn junctions
C. 2 pn junctions
D. one pn junction

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

A. MΩ
B. kΩ
C. Ω
D. none of the above

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

A. reverse
B. either forward or reverse
C. forward
D. none of the above

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

A. mA
B. μA
C. A
D. kA

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

A. 2.5 V
B. 3 V
C. 10 V
D. 0.7 V

6. A crystal diode is used as ……………

A. an amplifier
B. an oscillator
C. a voltage regulator
D. a rectifier

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

A. less than
B. same as
C. more than
D. none of the above

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

A. insulator
B. resistance material
C. none of the above
D. conductor

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

A. 40,000 : 1
B. 1000 : 1
C. 100 : 1
D. 1 : 1

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

A. majority carriers
B. junction capacitance
C. minority carriers
D. none of the above

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

A. remains the same
B. decreases
C. becomes zero
D. increases

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

A. the same as
B. more than
C. lower than
D. none of the above

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

A. remains the same
B. is increased
C. is decreased
D. none of the above

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

A. applied voltage
B. barrier potential
C. breakdown voltage
D. forward voltage

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

A. active
B. nonlinear
C. passive
D. linear

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

A. inverse
B. poor
C. reverse
D. forward

17. A crystal diode is a …………… device

A. non-linear
B. bilateral
C. linear
D. none of the above

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

A. reverse
B. forward or reverse
C. none of the above
D. forward

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

A. PIC rating
B. reverse characteristic
C. forward characteristic
D. doping level

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

A. remains the same
B. is decreased
C. in increased
D. none of the above

21. A zener diode has ………..

A. two pn junctions
B. three pn junctions
C. none of the above
D. one pn junction

22. A zener diode is used as …………….

A. an amplifier
B. a rectifier
C. a voltage regulator
D. a multivibrator

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

A. the same as
B. less than
C. more than
D. none of the above

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

A. forward
B. reverse
C. either reverse or forward
D. none of the above

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

A. forward
B. reverse
C. both forward and reverse
D. none of the above

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

A. constant current
B. constant resistance
C. none of the above
D. constant voltage

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

A. carrier more than rated current
B. is forward biased
C. is reverse biased
D. none of the above

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

A. properly reverse bias the zener
B. properly forward bias the zener
C. none of the above
D. protect the zener

29. A zener diode is …………………. device

A. a non-linear
B. a linear
C. an amplifying
D. none of the above

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

A. undefined
B. zero
C. sharp
D. none of the above

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

A. vacuum tube
B. gas tube
C. none of the above
D. solid state

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

A. lighting purposes
B. heaters
C. using in electronic equipment
D. none of the above

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

A. components are expensive
B. diodes must have a higher power rating
C. output is difficult to filter
D. none of the above

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

A. 400/√2 V
B. 400 V
C. 400 x √2 V
D. none of the above

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

A. 2
B. 1.21
C. 2.5
D. 0.48

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

A. half-wave rectifier
B.bridge full-wave rectifier
C. none of the above
D. centre-tap full-wave rectifier

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

A. one-half
B. the same as
C. twice
D. four times

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

A. twice
B. thrice
C. four time
D. one-half

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

A. the diode is destroyed
B. the diode conducts poorly
C. the diode behaves like a zener diode
D. none of the above

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

A. paper capacitor
B. mica capacitor
C. electrolytic capacitor
D. air capacitor