EE AND ECE IMPORTANT MCQ PDF- Regulated DC Power Supply 1

Q1. In an unregulated power supply, if load current increases, the output voltage ………..

1. Remains the same
2. Decreases
3. Increases
4. None of the above

Answer : 2
Q2. In an unregulated power supply, if input a.c. voltage increases, the output voltage …….

1. Increases
2. Decreases
3. Remains the same
4. None of the above

Answer : 1
Q3. A power supply which has voltage regulation of ……….. is unregulated power supply

1. 0 %
2. 5 %
3. 10 %
4. 8%

Answer : 3
Q4. Commercial power supplies have voltage regulation ………….

1. of 10%
2. of 15%
3. of 25%
4. within 1%

Answer : 4
Q5. An ideal regulated power supply is one which has voltage regulation of …………

1. 0%
2. 5%
3. 10%
4. 1%

Answer : 1
Q6. A Zener diode utilises ………… characteristic for voltage regulation

1. Forward
2. Reverse
3. Both forward and reverse
4. None of the above

Answer : 2
Q7. Zener diode can be used as …………

1. ac. voltage regulator only
2. dc. voltage regulator only
3. both d.c. and a.c. voltage regulator
4. none of the above

Answer : 3
Q8. A Zener diode is used as a …………… voltage regulating device

1. Shunt
2. Series
3. Series-shunt
4. None of the above

Answer : 1
Q9. As the junction temperature increases, the voltage breakdown point for Zener mechanism …………

1. Is increased
2. Is decreased
3. Remains the same
4. None of the above

Answer : 2
Q10. The rupture of co-valent bonds will occur when the electric field is ………….

1. 100 V/cm
2. 6 V/cm
3. 1000 V/cm
4. More than 105 V/cm

Answer : 4
Q11. In a 15 V Zener diode , the breakdown mechanism will occur by ………….

1. Avalanche mechanism
2. Zener mechanism
3. Both Zener and avalanche mechanism
4. None of the above

Answer : 1
Q12. A Zener diode that has very narrow depletion layer will breakdown by ……… mechanism

1. Avalanche
2. Zener
3. Both avalanche and Zener
4. None of the above

Answer : 2
Q13. As the junction temperature increases, the voltage breakdown point for avalanche mechanism ………….

1. Remains the same
2. Decrease
3. Increases
4. None of the above

Answer : 3
Q14. Another name for Zener diode is ………… diode

1. Breakdown
2. Voltage
3. Power
4. Current

Answer : 1
Q15. Zener diode are generally made of ……….

1. Germanium
2. Silicon
3. Carbon
4. None of the above

Answer : 2
Q16. For increasing the voltage rating, zeners are connected in …………..

1. Parallel
2. Series-parallel
3. Series
4. None of the above

Answer : 3
Q17. In a Zener voltage regulator, the changes in load current produce changes in …………….

1. Zener current
2. Zener voltage
3. Zener voltage as well as Zener current
4. None of the above

Answer : 1
Q18. A Zener voltage regulator is used for …………… load currents

1. High
2. Very high
3. Moderate
4. Small

Answer : 4
Q19. A Zener voltage regulator will cease to act as a voltage regulator if Zener current becomes ……………

1. Less than load current
2. Zero
3. More than load current
4. None of the above

Answer : 2
Q20. If the doping level is increased, the breakdown voltage of the Zener …………..

1. Remains the same
2. Is increased
3. Is decreased
4. None of the above

Answer : 3

Q21. A 30 V Zener will have depletion layer width …………. that of 10 V Zener

1. More than
2. Less than
3. Equal to
4. None of the above

Answer : 1
Q22. The current in a Zener diode is limited by …………..

1. External resistance
2. Power dissipation
3. Both (1) and (2)
4. None of the above

Answer : 3
Q23. A 5 mA changes in Zener current produces a 50 mA change in Zener voltage. What is the Zener impedance?

1. 1 Ω
2. 1 Ω
3. 100 Ω
4. 10 Ω

Answer : 4
Q24. 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?

1. 09%
2. 87 %
3. 72 %
4. None of the above

Answer : 1
Q25. What is true about the breakdown voltage in a Zener diode?

1. It decreases when load current increases
2. It destroys the diode
3. It equals current times the resistance
4. It is approximately constant

Answer : 4
Q26. Which of these is the best description for a Zener diode?

1. It is a diode
2. It is a constant current device
3. It is a constant-voltage device
4. It works in the forward region

Answer : 3
Q27. A Zener diode …………..

1. Is a battery
2. Acts like a battery in the breakdown region
3. Has a barrier potential of 1 V
4. Is forward biased

Answer : 2
Q28. The load voltage is approximately constant when a Zener diode is ……….

1. Forward biased
2. Unbiased
3. Reverse biased
4. Operating in the breakdown region

Answer : 4
Q29. In a loaded Zener regulator, which is the largest Zener current?

1. Series current
2. Zener current
3. Load current
4. None of the above

Answer : 1
Q30. If the load resistance decreases in a Zener regulator, then Zener current …………….

1. Decreases
2. Stays the same
3. Increases
4. None of the above

Answer : 1
Q31. 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?

1. 10%
2. 20%
3. 15%
4. 5%

Answer : 4
Q32. If the load current drawn by unregulated power supply increases, the d.c. output voltage ………..

1. Increases
2. Decreases
3. Stays the same
4. None of the above

Answer : 2
Q33. If the load current drawn by unregulated power supply increases, the d.c. output voltage ………

1. Increases
2. Decreases
3. Stays the same
4. None of the above

Answer : 2
Q34. A power supply has a voltage regulation of 1%. If the no-load  voltage is 20 V, what is the full-load voltage?

1. 8 V
2. 7 V
3. 6 V
4. 2 V

Answer : 1
Q35. Two similar 15 V Zeners are connected in series. What is the regulated output voltage?

1. 15 V
2. 5 V
3. 30 V
4. 45 V

Answer : 3
Q36. 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?

1. 10 Ω
2. 20 Ω
3. 15 Ω
4. 40 Ω

Answer : 4
Q37. 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?

1. 10 Ω
2. 50 Ω
3. 25 Ω
4. 40 Ω

Answer : 2
Q38. A Zener regulator …………… in the power supply

1. Increases the ripple
2. Decreases the ripple
3. Neither increases nor decreases the ripple
4. Data insufficient

Answer : 2
Q39. When load current is zero, the Zener current will be ………

1. Zero
2. Minimum
3. Maximum
4. None of the above

Answer : 3
Q40. The Zener current will be minimum when …………

1. Load current is maximum
2. Load current is minimum
3. Load current is zero
4. None of the above

Answer : 1
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