REGULATED D.C. POWER SUPPLY Questions with Answers :-
1. In an unregulated power supply, if load current increases, the output voltage ………..
- Remains the same
- Decreases
- Increases
- None of the above
Ans : 2
2. In an unregulated power supply, if input a.c. voltage increases, the output voltage …….
- Increases
- Decreases
- Remains the same
- None of the above
Ans : 1
3. A power supply which has voltage regulation of ……….. is unregulated power supply
- 0 %
- 5 %
- 10 %
- 8%
Ans : 3
4. Commercial power supplies have voltage regulation ………….
- of 10%
- of 15%
- of 25%
- within 1%
Ans : 4
5. An ideal regulated power supply is one which has voltage regulation of …………
- 0%
- 5%
- 10%
- 1%
Ans : 1
6. A Zener diode utilises ………… characteristic for voltage regulation
Forward
Reverse
Both forward and reverse
None of the above
Ans : 2
7. Zener diode can be used as …………
c. voltage regulator only
c. voltage regulator only
both d.c. and a.c. voltage regulator
none of the above
Ans : 3
8. A Zener diode is used as a …………… voltage regulating device
Shunt
Series
Series-shunt
None of the above
Ans : 1
9. As the junction temperature increases, the voltage breakdown point for Zener mechanism …………
Is increased
Is decreased
Remains the same
None of the above
Ans : 2
10. The rupture of co-valent bonds will occur when the electric field is ………….
100 V/cm
6 V/cm
1000 V/cm
More than 105 V/cm
Ans : 4
11. In a 15 V Zener diode , the breakdown mechanism will occur by ………….
Avalanche mechanism
Zener mechanism
Both Zener and avalanche mechanism
None of the above
Ans : 1
12. A Zener diode that has very narrow depletion layer will breakdown by ……… mechanism
Avalanche
Zener
Both avalanche and Zener
None of the above
Ans : 2
13. As the junction temperature increases, the voltage breakdown point for avalanche mechanism ………….
Remains the same
Decrease
Increases
None of the above
Ans : 3
14. Another name for Zener diode is ………… diode
Breakdown
Voltage
Power
Current
Ans : 1
15. Zener diode are generally made of ……….
Germanium
Silicon
Carbon
None of the above
Ans : 2
16. For increasing the voltage rating, zeners are connected in …………..
Parallel
Series-parallel
Series
None of the above
Ans : 3
17. In a Zener voltage regulator, the changes in load current produce changes in …………….
Zener current
Zener voltage
Zener voltage as well as Zener current
None of the above
Ans : 1
18. A Zener voltage regulator is used for …………… load currents
High
Very high
Moderate
Small
Ans : 4
19. A Zener voltage regulator will cease to act as a voltage regulator if Zener current becomes ……………
Less than load current
Zero
More than load current
None of the above
Ans : 2
20. If the doping level is increased, the breakdown voltage of the Zener …………..
Remains the same
Is increased
Is decreased
None of the above
Ans : 3
21. A 30 V Zener will have depletion layer width …………. that of 10 V Zener
More than
Less than
Equal to
None of the above
Ans : 1
22. The current in a Zener diode is limited by …………..
External resistance
Power dissipation
Both (1) and (2)
None of the above
Ans : 3
23. A 5 mA changes in Zener current produces a 50 mA change in Zener voltage. What is the Zener impedance?
1 O
1 O
100 O
10 O
Ans : 4
24. 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?
09%
87 %
72 %
None of the above
Ans : 1
25. What is true about the breakdown voltage in a Zener diode?
It decreases when load current increases
It destroys the diode
It equals current times the resistance
It is approximately constant
Ans : 4
26. Which of these is the best description for a Zener diode?
It is a diode
It is a constant current device
It is a constant-voltage device
It works in the forward region
Ans : 3
27. A Zener diode …………..
Is a battery
Acts like a battery in the breakdown region
Has a barrier potential of 1 V
Is forward biased
Ans : 2
28. The load voltage is approximately constant when a Zener diode is ……….
Forward biased
Unbiased
Reverse biased
Operating in the breakdown region
Ans : 4
29. In a loaded Zener regulator, which is the largest Zener current?
Series current
Zener current
Load current
None of the above
Ans : 1
30. If the load resistance decreases in a Zener regulator, then Zener current …………….
Decreases
Stays the same
Increases
None of the above
Ans : 1
31. 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?
10%
20%
15%
5%
Ans : 4
32. If the load current drawn by unregulated power supply increases, the d.c. output voltage ………..
Increases
Decreases
Stays the same
None of the above
Ans : 2
33. If the load current drawn by unregulated power supply increases, the d.c. output voltage ………
Increases
Decreases
Stays the same
None of the above
Ans : 2
34. A power supply has a voltage regulation of 1%. If the no-load voltage is 20 V, what is the full-load voltage?
8 V
7 V
6 V
2 V
Ans : 1
35. Two similar 15 V Zeners are connected in series. What is the regulated output voltage?
15 V
5 V
30 V
45 V
Ans : 3
36. 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?
10 O
20 O
15 O
40 O
Ans : 4
37. 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?
10 O
50 O
25 O
40 O
Ans : 2
38. A Zener regulator …………… in the power supply
Increases the ripple
Decreases the ripple
Neither increases nor decreases the ripple
Data insufficient
Ans : 2
39. When load current is zero, the Zener current will be ………
Zero
Minimum
Maximum
None of the above
Ans : 3
40. The Zener current will be minimum when …………
Load current is maximum
Load current is minimum
Load current is zero
None of the above
Ans : 1