Regulated Power Supplies – Exercise – 1

1. Regulation of a D.C. power supply is given by :

(a)  product of no-load output voltage and full-load current
(b)  ratio of full-load output voltage and full-load current
(c)  change in output voltage from no-load to full-load
(d)  change in output impedance from no-load to full-load

Answer
Answer : (d)
Explanation
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2. In an unregulated power supply, if load current increases, the output voltage ………..

(a)  remains the same
(b)  decreases
(c)  increases
(d)  none of the above

Answer
Answer : (b)
Explanation
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3. In an unregulated power supply, if input a.c. voltage increases, the output voltage ……….

(a)  increases
(b)  decreases
(c)  remains the same
(d)  none of the above

Answer
Answer : (a)
Explanation
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4. A power supply which has a voltage regulation of ……….. is unregulated power supply.

(a)  0 %
(b)  0.5 %
(c)  10 %
(d)  0.8 %

Answer
Answer : (c)
Explanation
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5. Commercial power supplies have voltage regulation ………..

(a)  of 10 %
(b)  of 15 %
(c)  of 25 %
(d)  within 1 %

Answer
Answer : (d)
Explanation
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6. An ideal regulated power supply is one which has voltage regulation of ………..

(a)  0 %
(b)  5 %
(c)  10 %
(d)  1 %

Answer
Answer : (a)
Explanation
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7. A zener diode utilises ……….. characteristic for voltage regulation.

(a)  forward
(b)  reverse
(c)  both forward and reverse
(d)  none of the above

Answer
Answer : (b)
Explanation
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8. Zener diode can be used as ………….

(a)  d.c. voltage regulator only
(b)  a.c. voltage regulator only
(c)  both d.c. and a.c. voltage regulator
(d)  none of the above

Answer
Answer : (c)
Explanation
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9. A zener diode is used as a ………… voltage regulating device.

(a)  shunt
(b)  series
(c)  series-shunt
(d)  none of the above

Answer
Answer : (a)
Explanation
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10. As the junction temperature increases, the voltage breakdown point for zener mechanism …………

(a)  is increased
(b)  is decreased
(c)  remains the same
(d)  none of the above

Answer
Answer : (b)
Explanation
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11. The rupture of co-valent bonds will occur when the electric field is …………

(a)  100 V/cm
(b)  0.6 V/cm
(c)  1000 V/cm
(d)  more than 105 V/cm

Answer
Answer : (d)
Explanation
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12. In a 15 V zener diode, the breakdown mechanism will occur by …………

(a)  avalanche mechanism
(b)  zener mechanism
(c)  both zener and avalanche mechanism
(d)  none of the above

Answer
Answer : (a)
Explanation
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13. In a zener voltage regulator, the changes in load current produce changes in ……….

(a)  zener current
(b)  zener voltage
(c)  zener voltage as well as zener current
(d)  none of the above

Answer
Answer : (a)
Explanation
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14. A zener voltage regulator is used for ………… load currents.

(a)  high
(b)  very high
(c)  moderate
(d)  small

Answer
Answer : (d)
Explanation
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15. A zener voltage regulator will cease to act as a voltage regulator if zener current becomes …………

(a)  less than load current
(b)  zero
(c)  more than load current
(d)  none of the above

Answer
Answer : (b)
Explanation
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16. If the doping level is increased, the breakdown voltage of the zener …………

(a)  remains the same
(b)  is increased
(c)  is decreased
(d)  none of the above

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
17. A 30 V zener will have depletion layer width ………… that of 10 V zener.

(a)  more than
(b)  less than
(c)  equal to
(d)  none of the above

Answer
Answer : (a)
Explanation
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18. The current in a zener diode is limited by …………

(a)  external resistance
(b)  power dissipation
(c)  both a and b
(d)  none of the above

Answer
Answer : (c)
Explanation
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19. A 5 mA change in zener current produces a 50 mV change in zener voltage. What is the zener impedance ?

(a)  1 Ω
(b)  0.1 Ω
(c)  100 Ω
(d)  10 Ω

Answer
Answer : (d)
Explanation
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20. 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 ?

(a)  3.09 %
(b)  2.87 %
(c)  5.72 %
(d)  none of the above

Answer
Answer : (a)
Explanation
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(a) (b) (c) (d) Answer : () [/su_spoiler]
Explanation
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22. Which of these is the best description for a zener diode ?

(a)  It is a diode.
(b)  It is a constant-current device
(c)  It is a constant-voltage device.
(d)  It works in the forward region

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
23. A zener diode …………

(a)  is a battery
(b)  acts like a battery in the breakdown region
(c)  has a barrier potential of 1 V
(d)  is forward biased

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
24. The load voltage is approximately constant when a zener diode is …………

(a)  forward biased
(b)  unbiased
(c)  reverse biased
(d)  operating in the breakdown region

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
25. In a loaded zener regulator, which is the largest zener current ?

(a)  series current
(b)  zener current
(c)  load current
(d)  none of the above

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
26. If the load resistance decreases in a zener regulator, then zener current ………….

(a)  decreases
(b)  stays the same
(c)  increases
(d)  none of the above

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
27. If the input a.c. voltage to unregulated or ordinary power supply increases by 5 %, what will be the approximate change in d.c. output voltage ?

(a)  10 %
(b)  20 %
(c)  15 %
(d)  5 %

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
28. If the load current drawn by unregulated power supply increases, the d.c. output voltage …………

(a)  increases
(b)  decreases
(c)  stays the same
(d)  none of the above

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
29. If a power supply has no-load and full-load voltages of 30 V and 25 V respectively, then percentage voltage regulation is …………

(a)  10 %
(b)  20 %
(c)  15 %
(d)  none of the above

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
30. A power supply has a voltage regulation of 1 %. If the no-load voltage is 20 V, what is the full-load voltage ?

(a)  20.8 V
(b)  15.7 V
(c)  18.6 V
(d)  17.2 V

Answer
Answer : (a)
Explanation
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31. Two similar 15 V zeners are connected in series. What is the regulated output voltage ?

(a)  15 V
(b)  7.5 V
(c)  30 V
(d)  45 V

Answer
Answer : (c)
Explanation
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32. 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 ?

(a)  10 Ω
(b)  20 Ω
(c)  15 Ω
(d)  40 Ω

Answer
Answer : (d)
Explanation
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33. 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 series resistance ?

(a)  10 Ω
(b)  50 Ω
(c)  25 Ω
(d)  40 Ω

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
34. A zener regulator …………… in the power supply.

(a)  increases the ripple
(b)  decreases the ripple
(c)  neither increases nor decreases ripple
(d)  data insufficient

Answer
Answer : (b)
Explanation
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35. When load current is zero, the zener current will be …………

(a)  zero
(b)  minimum
(c)  maximum
(d)  none of the above

Answer
Answer : (c)
Explanation
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36. The zener current will be minimum when …………

(a)  load current is maximum
(b)  load current is minimum
(c)  load current is zero
(d)  none of the above

Answer
Answer : (a)
Explanation
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