This is the Multiple Choice Questions (MCQs) in Chapter 21: Power Supplies from the book Teach Yourself Electricity and Electronics, 5th edition by Stan Gibilisco. If you are looking for a reviewer in Electronics Engineering this will definitely help you before taking the Board Exam.
Start Practice Exam Test Questions
1. The output of a rectifier is:
- A. 60-Hz ac.
- B. Smooth dc.
- C. Pulsating dc.
- D. 120-Hz ac.
2. Which of the following might not be needed in a power supply?
- A. The transformer.
- B. The filter.
- C. The rectifier.
- D. All of the above are generally needed.
3. Of the following appliances, which would need the biggest transformer?
- A. A clock radio.
- B. A TV broadcast transmitter.
- C. A shortwave radio receiver.
- D. A home TV set.
4. An advantage of full-wave bridge rectification is:
- A. It uses the whole transformer secondary for the entire ac input cycle.
- B. It costs less than other rectifier types.
- C. It cuts off half of the ac wave cycle.
- D. It never needs a regulator.
5. In. a supply designed to provide high power at low voltage, the best rectifier design would probably be:
- A. Half-wave.
- B. Full-wave, center-tap.
- C. Bridge.
- D. Voltage multiplier.
6. The part of a power supply immediately preceding the regulator is:
- A. The transformer.
- B. The rectifier.
- C. The filter.
- D. The ac input.
7. If a half-wave rectifier is used with 117-V rms ac (house mains), the average dc output voltage is about:
- A. 52.7 V.
- B. 105 V.
- C. 117 V.
- D. 328 V.
8. If a full-wave bridge circuit is used with a transformer whose secondary provides 50 V rms, the PIV across the diodes is about:
- A. 50 V.
- B. 70 V.
- C. 100 V.
- D. 140 V.
9. The principal disadvantage of a voltage multiplier is:
- A. Excessive current.
- B. Excessive voltage.
- C. Insufficient rectification.
- D. Poor regulation.
10. A transformer secondary provides 10 V rms to a voltage-doubler circuit. The dc output voltage is about:
- A. 14 V.
- B. 20 V.
- C. 28 V.
- D. 36 V.
11. The ripple frequency from a full-wave rectifier is:
- A. Twice that from a half-wave circuit.
- B. The same as that from a half-wave circuit.
- C. Half that from a half-wave circuit.
- D. One-fourth that from a half-wave circuit.
12. Which of the following would make the best filter for a power supply?
- A. A capacitor in series.
- B. A choke in series.
- C. A capacitor in series and a choke in parallel.
- D. A capacitor in parallel and a choke in series.
13. If you needed exceptionally good ripple filtering for a power supply, the best approach would be to:
- A. Connect several capacitors in parallel.
- B. Use a choke-input filter.
- C. Connect several chokes in series.
- D. Use two capacitor/choke sections one after the other.
14. Voltage regulation can be accomplished by a Zener diode connected in:
- A. Parallel with the filter output, forward-biased.
- B. Parallel with the filter output, reverse-biased.
- C. Series with the filter output, forward-biased.
- D. Series with the filter output, reverse-biased.
15. A current surge takes place when a power supply is first turned on because:
- A. The transformer core is suddenly magnetized.
- B. The diodes suddenly start to conduct.
- C. The filter capacitor(s) must be initially charged.
- D. Arcing takes place in the power switch.
16. Transient suppression minimizes the chance of:
- A. Diode failure.
- B. Transformer failure.
- C. Filter capacitor failure.
- D. Poor voltage regulation.
17. If a fuse blows, and it is replaced with one having a lower current rating, there’s a good chance that:
- A. The power supply will be severely damaged.
- B. The diodes will not rectify.
- C. The fuse will blow out right away.
- D. Transient suppressors won’t work.
18. A fuse with nothing but a straight wire inside is probably:
- A. A slow-blow type.
- B. A quick-break type.
- C. Of a low current rating.
- D. Of a high current rating.
19. Bleeder resistors are:
- A. Connected in parallel with filter capacitors.
- B. Of low ohmic value.
- C. Effective for transient suppression.
- D. Effective for surge suppression.
20. To service a power supply with which you are not completely familiar, you should:
- A. Install bleeder resistors.
- B. Use proper fusing.
- C. Leave it alone and have a professional work on it.
- D. Use a voltage regulator.