Power Supplies - Gibilisco MCQs in Electronics

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.

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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.

Complete List of Multiple Choice Questions from this Book

Multiple Choice Questions in Teach Yourself Electricity and Electronics

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