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regulated d c power supply MCQs

Practise focused regulated d c power supply questions with marked answers for exam preparation and subject revision.

regulated d c power supply Mcqs

1. If the load current drawn by unregulated power supply increases, the d.c. output voltage _____________?
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A. Decreases

B. Stays the same

C. Increases

D. None of the above

2. A Zener diode is used as a _____________voltage regulating device?
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A. Series-shunt

B. None of the above

C. Series

D. Shunt

3. Commercial power supplies have voltage regulation ______________?
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A. within 1%

B. of 15%

C. of 10%

D. of 25%

4. If the doping level is increased, the breakdown voltage of the Zener_______________?
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A. None of the above

B. Remains the same

C. Is decreased

D. Is increased

5. A 5 mA changes in Zener current produces a 50 mA change in Zener voltage. What is the Zener impedance ?
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A. 1 O

B. 1 O

C. 100 O

D. 10 O

6. Which of these is the best description for a Zener diode ?
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A. It works in the forward region

B. It is a constant-voltage device

C. It is a constant current device

D. It is a diode

7. As the junction temperature increases, the voltage breakdown point for Zener mechanism _______________?
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A. Remains the same

B. Is increased

C. None of the above

D. Is decreased

8. What is true about the breakdown voltage in a Zener diode ?
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A. It equals current times the resistance

B. It is approximately constant

C. It decreases when load current increases

D. It destroys the diode

9. For increasing the voltage rating, zeners are connected in_____________?
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A. Series-parallel

B. Parallel

C. Series

D. None of the above

10. The rupture of co-valent bonds will occur when the electric field is__________________?
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A. 1000 V/cm

B. 6 V/cm

C. More than 105 V/cm

D. 100 V/cm

11. When load current is zero, the Zener current will be_____________?
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A. Zero

B. Minimum

C. None of the above

D. Maximum

12. A power supply can deliver a maximum rated current of 0.5 A at full-load output voltage of 20 V. What is the minimum load resistance that you can connect across the supply?
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A. 10 O

B. 40 O

C. 15 O

D. 20 O

13. A Zener regulator _____________ in the power supply?
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A. Increases the ripple

B. Decreases the ripple

C. Data insufficient

D. Neither increases nor decreases the ripple

14. In an unregulated power supply, if input a.c. voltage increases, the output voltage _______________?
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A. Increases

B. Remains the same

C. None of the above

D. Decreases

15. A power supply which has voltage regulation of ____________ is unregulated power supply?
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A. 10 %

B. 5%

C. 0%

D. 8%

16. Zener diode can be used as__________________?
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A. c. voltage regulator only

B. c. voltage regulator only

C. both D.C and A.C voltage regulator

D. none of the above

17. A Zener voltage regulator is used for ____________ load currents?
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A. Small

B. High

C. Very high

D. Moderate

18. In a regulated power supply, two similar 15 V zeners are connected in series. The input voltage is 45 V d.c. If each Zener has a maximum current rating of 300 mA, what should be the value of the series resistance ?
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A. 25 O

B. 10 O

C. 40 O

D. 50 O

19. A certain regulator has a no-load voltage of 6 V and a full-load output of 5.82 V. What is the load regulation ?
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A. 09%

B. None of the above

C. 87%

D. 72%

20. Zener diode are generally made of _____________?
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A. Germanium

B. None of the above

C. Carbon

D. Silicon

21. If the load current drawn by unregulated power supply increases, the d.c. output voltage______________?
0

A. Decreases

B. None of the above

C. Stays the same

D. Increases

22. A power supply has a voltage regulation of 1%. If the no-load voltage is 20 V, what is the full-load voltage ?
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A. 2 V

B. 6 V

C. 7 V

D. 8 V

23. An ideal regulated power supply is one which has voltage regulation of________________?
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A. 5%

B. 0%

C. 10%

D. 1%

24. As the junction temperature increases, the voltage breakdown point for avalanche mechanism______________?
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A. Increases

B. Remains the same

C. None of the above

D. Decrease

25. The current in a Zener diode is limited by _______________?
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A. External resistance

B. Power dissipation

C. Both (A) and (B)

D. None of the above

26. If the load resistance decreases in a Zener regulator, then Zener current ______________?
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A. Stays the same

B. None of the above

C. Increases

D. Decreases

27. The Zener current will be minimum when_____________?
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A. Load current is minimum

B. Load current is maximum

C. Load current is zero

D. None of the above

28. A 30 V Zener will have depletion layer width_______________ that of 10 V Zener?
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A. Equal to

B. More than

C. None of the above

D. Less than

29. In a Zener voltage regulator, the changes in load current produce changes in _________________?
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A. Zener voltage as well as Zener current

B. Zener voltage

C. None of the above

D. Zener current

30. A Zener diode utilises_____________characteristic for voltage regulation?
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A. Forward

B. Reverse

C. Both forward and reverse

D. None of the above

31. In an unregulated power supply, if load current increases, the output voltage _____________?
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A. Increases

B. None of the above

C. Decreases

D. Remains the same

32. In a 15 V Zener diode , the breakdown mechanism will occur by ______________?
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A. Avalanche mechanism

B. Zener mechanism

C. Both Zener and avalanche mechanism

D. None of the above

33. If the input a.c. voltage to regulated or ordinary power supply increases by 5% what will be the approximate change in d.c. output voltage?
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A. 5%

B. 20%

C. 10%

D. 15%

34. The load voltage is approximately constant when a Zener diode is ________________?
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A. Unbiased

B. Operating in the breakdown region

C. Reverse biased

D. Forward biased

35. A Zener voltage regulator will cease to act as a voltage regulator if Zener current becomes______________?
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A. None of the above

B. More than load current

C. Zero

D. Less than load current

A. 30 V

B. 45 V

C. 15 V

D. 5 V

37. A Zener diode______________?
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A. Is a battery

B. Acts like a battery in the breakdown region

C. Is forward biased

D. Has a barrier potential of 1 V

38. A Zener diode that has very narrow depletion layer will breakdown by____________ mechanism?
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A. Avalanche

B. Zener

C. Both avalanche and Zener

D. None of the above

39. Another name for Zener diode is ______________diode?
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A. Voltage

B. Power

C. Breakdown

D. Current

40. In a loaded Zener regulator, which is the largest Zener current ?
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A. None of the above

B. Series current

C. Load current

D. Zener current

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