## Multiple Choice Questions and Answers on Regulated DC Power Supply

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

- Remains the same
- Decreases
- Increases
- None of the above

**Answer : 2**

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

- Increases
- Decreases
- Remains the same
- None of the above

**Answer : 1**

**Q3. A power supply which has voltage regulation of ……….. is unregulated power supply**

- 0 %
- 5 %
- 10 %
- 8%

**Answer : 3**

**Q4. Commercial power supplies have voltage regulation ………….**

- of 10%
- of 15%
- of 25%
- within 1%

**Answer : 4**

**Q5. An ideal regulated power supply is one which has voltage regulation of …………**

- 0%
- 5%
- 10%
- 1%

**Answer : 1**

**Q6. A Zener diode utilises ………… characteristic for voltage regulation**

- Forward
- Reverse
- Both forward and reverse
- None of the above

**Answer : 2**

**Q7. 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

**Answer : 3**

**Q8. A Zener diode is used as a …………… voltage regulating device**

- Shunt
- Series
- Series-shunt
- None of the above

**Answer : 1**

**Q9. As the junction temperature increases, the voltage breakdown point for Zener mechanism …………**

- Is increased
- Is decreased
- Remains the same
- None of the above

**Answer : 2**

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

- 100 V/cm
- 6 V/cm
- 1000 V/cm
- More than 10
^{5}V/cm

**Answer : 4**

**Q11. 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

**Answer : 1**

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

- Avalanche
- Zener
- Both avalanche and Zener
- None of the above

**Answer : 2**

**Q13. As the junction temperature increases, the voltage breakdown point for avalanche mechanism ………….**

- Remains the same
- Decrease
- Increases
- None of the above

**Answer : 3**

**Q14. Another name for Zener diode is ………… diode**

- Breakdown
- Voltage
- Power
- Current

**Answer : 1**

**Q15. Zener diode are generally made of ……….**

- Germanium
- Silicon
- Carbon
- None of the above

**Answer : 2**

**Q16. For increasing the voltage rating, zeners are connected in …………..**

- Parallel
- Series-parallel
- Series
- None of the above

**Answer : 3**

**Q17. 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

**Answer : 1**

**Q18. A Zener voltage regulator is used for …………… load currents**

- High
- Very high
- Moderate
- Small

**Answer : 4**

**Q19. 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

**Answer : 2**

**Q20. If the doping level is increased, the breakdown voltage of the Zener …………..**

- Remains the same
- Is increased
- Is decreased
- None of the above

**Answer : 3**

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

- More than
- Less than
- Equal to
- None of the above

**Answer : 1**

**Q22. The current in a Zener diode is limited by …………..**

- External resistance
- Power dissipation
- Both (1) and (2)
- 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 Ω
- 1 Ω
- 100 Ω
- 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?**

- 09%
- 87 %
- 72 %
- None of the above

**Answer : 1**

**Q25. 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

**Answer : 4**

**Q26. 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

**Answer : 3**

**Q27. A Zener diode …………..**

- Is a battery
- Acts like a battery in the breakdown region
- Has a barrier potential of 1 V
- Is forward biased

**Answer : 2**

**Q28. The load voltage is approximately constant when a Zener diode is ……….**

- Forward biased
- Unbiased
- Reverse biased
- Operating in the breakdown region

**Answer : 4**

**Q29. In a loaded Zener regulator, which is the largest Zener current?**

- Series current
- Zener current
- Load current
- None of the above

**Answer : 1**

**Q30. If the load resistance decreases in a Zener regulator, then Zener current …………….**

- Decreases
- Stays the same
- Increases
- 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?**

- 10%
- 20%
- 15%
- 5%

**Answer : 4**

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

- Increases
- Decreases
- Stays the same
- None of the above

**Answer : 2**

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

- Increases
- Decreases
- Stays the same
- 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?**

- 8 V
- 7 V
- 6 V
- 2 V

**Answer : 1**

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

- 15 V
- 5 V
- 30 V
- 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?**

- 10 Ω
- 20 Ω
- 15 Ω
- 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?**

- 10 Ω
- 50 Ω
- 25 Ω
- 40 Ω

**Answer : 2**

**Q38. A Zener regulator …………… in the power supply**

- Increases the ripple
- Decreases the ripple
- Neither increases nor decreases the ripple
- Data insufficient

**Answer : 2**

**Q39. When load current is zero, the Zener current will be ………**

- Zero
- Minimum
- Maximum
- None of the above

**Answer : 3**

**Q40. The Zener current will be minimum when …………**

- Load current is maximum
- Load current is minimum
- Load current is zero
- None of the above

**Answer : 1**

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