# Gibilisco - Power Supplies Quiz

Reviewed by Matt Balanda
Matt Balanda, BS (Aerospace Engineering) |
Physics
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Matt holds a Bachelor's of Science in Aerospace Engineering and Mathematics from the University of Arizona, along with a Master's in Educational Leadership for Faith-Based Schools from California Baptist University. A devoted leader, he transitioned from Aerospace Engineering to inspire students. As the High School Vice-Principal and a skilled Physics teacher at Calvary Chapel Christian School, his passion is nurturing a love for learning and deepening students' connection with God, fostering a transformative educational journey.
, BS (Aerospace Engineering)
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Is your take on electronics subject really good? Can you answer all these questions related to the book power supplies by Stan Gibilisco? If so, take this quiz and see for yourself. This book includes questions and answers related to alternating current (AC), power supplies, wires, cables, and transformers. This is the overall reading material for all the electronics and electrical engineering students. The below quiz contains some of the important questions from this book. So, if you want to learn about power supplies, check out the quiz.

## Gibilisco - Power Supplies Questions and Answers

• 1.

### The output of a rectifier circuit without a filter included is

• A.

60 Hz ac.

• B.

Smooth dc.

• C.

Pulsating dc.

• D.

120 Hz ac.

C. Pulsating dc.
Explanation
A rectifier circuit converts alternating current (ac) into direct current (dc). However, without a filter included, the output of the rectifier circuit will still contain ripples or variations in voltage. This type of output is known as pulsating dc, where the voltage rises and falls but does not reverse direction like in ac. Therefore, the correct answer is pulsating dc.

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• 2.

### Which of the following components is not necessarily required in a power supply designed to produce 12-V dc output with 117-V rms ac input?

• A.

The transformer

• B.

The filter

• C.

The rectifier

• D.

All of the above components are required.

D. All of the above components are required.
Explanation
In order to produce a 12-V dc output with a 117-V rms ac input, all of the listed components are necessary. The transformer is needed to step down the voltage from the ac input to a suitable level for rectification. The rectifier is required to convert the ac input to dc output. Lastly, the filter is necessary to smooth out any remaining ripples or fluctuations in the dc output. Therefore, all of these components are essential for the power supply to function properly.

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• 3.

### Of the following appliances, which would need the biggest transformer?

• A.

• B.

• C.

• D.

A home television set

Explanation
A television broadcast transmitter would need the biggest transformer because it requires a large amount of power to transmit television signals over long distances. Transmitters typically operate at high power levels, often in the kilowatt range, compared to the other appliances listed. Therefore, it would require a larger transformer to handle the higher power demands of the television broadcast transmitter compared to the other appliances.

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• 4.

### An advantage of full-wave bridge rectification is the fact that

• 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 filter.

A. It uses the whole transformer secondary for the entire ac input cycle.
Explanation
Full-wave bridge rectification is advantageous because it utilizes the entire transformer secondary for the entire AC input cycle. This means that both the positive and negative halves of the AC waveform are utilized, resulting in a more efficient conversion of AC to DC. This allows for a higher average output voltage and a smoother DC output compared to other rectifier types that only utilize half of the AC wave cycle.

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• 5.

### In a power supply designed to provide high power at low voltage, the best rectifier circuit would probably be the

• A.

Half-wave arrangement.

• B.

Full-wave, center-tap arrangement.

• C.

Quarter-wave arrangement.

• D.

Voltage doubler arrangement.

B. Full-wave, center-tap arrangement.
Explanation
The full-wave, center-tap arrangement is the best rectifier circuit for a power supply designed to provide high power at low voltage. This circuit utilizes both halves of the input AC waveform, resulting in a higher average output voltage compared to the half-wave arrangement. The center-tap provides a reference point for the circuit, allowing for more efficient voltage conversion. Additionally, the full-wave arrangement reduces ripple and provides a smoother DC output, making it suitable for high-power applications. The quarter-wave arrangement and voltage doubler arrangement are not as efficient or effective in providing high power at low voltage.

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• 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.

C. The filter.
Explanation
The part of a power supply immediately preceding the regulator is the filter. The filter is responsible for removing any unwanted noise or fluctuations in the input voltage. It smooths out the rectified AC voltage from the transformer and ensures a stable and clean DC voltage is supplied to the regulator. This helps in providing a steady power output and protects the electronic components from any voltage spikes or disturbances.

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• 7.

### If a half-wave rectifier is used with 165-V pk ac input, the effective dc output voltage is

• A.

Considerably less than 165 V.

• B.

Slightly less than 165 V.

• C.

Exactly 165 V.

• D.

Slightly more than 165 V.

A. Considerably less than 165 V.
Explanation
A half-wave rectifier only allows the positive half of the input AC waveform to pass through, while blocking the negative half. This means that the output waveform will have a lower peak voltage than the input. Additionally, there will be some voltage drop across the rectifier diode. As a result, the effective DC output voltage will be considerably less than the peak voltage of the AC input.

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• 8.

### If a full-wave bridge circuit is used with a transformer whose secondary provides 50 V rms, the peak voltage that occurs across the diodes in the reverse direction is approximately

• A.

50 V pk.

• B.

70 V pk.

• C.

100 V pk.

• D.

140 V pk.

B. 70 V pk.
Explanation
In a full-wave bridge circuit, the peak voltage across the diodes in the reverse direction is approximately 1.4 times the rms voltage of the transformer's secondary. Since the rms voltage is 50 V, the peak voltage would be 1.4 times that, which is 70 V pk.

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• 9.

### What is the principal disadvantage of a voltage-doubler power supply circuit?

• A.

Excessive current

• B.

Excessive voltage

• C.

Insufficient rectification

• D.

D. Poor regulation under heavy loads
Explanation
The principal disadvantage of a voltage-doubler power supply circuit is poor regulation under heavy loads. This means that when the circuit is operating with a high power demand, it is unable to maintain a stable and consistent output voltage. This can lead to fluctuations in the power supply, causing potential damage to the connected devices or affecting their performance.

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• 10.

### Suppose a secondary transformer provides 10-V RMS AC to a voltage-doubler circuit. What is the approximate DC output voltage with no load?

• A.

14 V

• B.

20 V

• C.

28 V

• D.

36 V

B. 20 V
Explanation
In a voltage-doubler circuit, the peak output voltage (V_dc) can be approximated as twice the RMS (root mean square) voltage of the AC input when there is no load.

Given that the transformer secondary provides 10-V RMS AC, we can calculate the approximate DC output voltage as follows:

V_dc ≈ 2 x V_rms
V_dc ≈ 2 x 10 V
V_dc ≈ 20 V

So, the approximate DC output voltage with no load is 20 volts.

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• 11.

### The ripple frequency from a full-wave rectifier is

• A.

Twice that of a half-wave circuit.

• B.

The same as that of a half-wave circuit.

• C.

Half that of a half-wave circuit.

• D.

1⁄4 that of a half-wave circuit.

A. Twice that of a half-wave circuit.
Explanation
A full-wave rectifier converts both the positive and negative halves of an alternating current (AC) signal into a direct current (DC) signal. This is achieved by using two diodes and a center-tapped transformer. Since the full-wave rectifier uses both halves of the AC signal, it produces twice as many pulses per cycle compared to a half-wave circuit. Therefore, the ripple frequency from a full-wave rectifier is twice that from a half-wave circuit.

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• 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

D. A capacitor in parallel and a choke in series
Explanation
A capacitor in parallel and a choke in series would make the best filter for a power supply. The capacitor in parallel helps to smooth out the voltage by storing and releasing electrical energy, while the choke in series helps to block high-frequency noise and ripple currents. This combination of components effectively filters out both high-frequency noise and low-frequency ripple, resulting in a cleaner and more stable power supply output.

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• 13.

### 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.

B. Parallel with the filter output, reverse-biased.
Explanation
A Zener diode connected in parallel with the filter output, reverse-biased, can be used for voltage regulation. When the voltage across the diode exceeds the Zener voltage, it starts conducting in reverse bias and maintains a constant voltage across it. This helps in regulating the output voltage and preventing it from exceeding a certain value.

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• 14.

### 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.

C. The filter capacitor(s) must be initially charged.
Explanation
When a power supply is first turned on, a current surge takes place because the filter capacitor(s) must be initially charged. The filter capacitor acts as a reservoir for electrical energy and helps in smoothing out the voltage fluctuations. When the power supply is turned on, the capacitor is initially discharged and needs to be charged up to its operating voltage. This sudden charging of the capacitor requires a large amount of current, resulting in a surge. Once the capacitor is fully charged, the current flow stabilizes.

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• 15.

### Transient suppression is of importance mainly because it minimizes the risk of

• A.

Diode failure.

• B.

Transformer imbalance.

• C.

Filter capacitor overcharging.

• D.

Poor voltage regulation.

A. Diode failure.
Explanation
Transient suppression is important because it helps to minimize the risk of diode failure. Transients, or sudden voltage spikes, can cause excessive current to flow through a diode, leading to its failure. By implementing transient suppression techniques such as using diode clamps or voltage suppressors, the voltage spikes can be limited, protecting the diodes from damage. This ensures the proper functioning and longevity of the diodes in electronic circuits.

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• 16.

### Suppose you see a fuse with nothing but a straight wire inside. You can assume that this fuse

• A.

Is a slow-blow type.

• B.

Is a quick-break type.

• C.

Has a low current rating.

• D.

Has a high current rating.

B. Is a quick-break type.
Explanation
The given answer, "is a quick-break type," is the correct explanation. A quick-break fuse is designed to quickly interrupt the flow of current when it exceeds a certain threshold. This type of fuse is commonly used in situations where the circuit needs to be protected from high current surges or short circuits. Since the fuse contains nothing but a straight wire, it suggests that it is designed to break the circuit rapidly in the event of excessive current flow.

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• 17.

### In order to minimize the risk of diode destruction as a result of surge currents that can occur when a power supply is first switched on, which of the following techniques can be useful?

• A.

Connecting multiple diodes in series, with low-value resistors across each diode

• B.

Connecting multiple diodes in parallel, with low-value resistors in series with each diode

• C.

Connecting multiple diodes in parallel, with low-value capacitors in series with each diode

• D.

Connecting multiple diodes in series, with low-value chokes across each diode

B. Connecting multiple diodes in parallel, with low-value resistors in series with each diode
Explanation
Connecting multiple diodes in parallel helps distribute the surge current among the diodes, reducing the risk of destruction. By adding low-value resistors in series with each diode, it further limits the current flowing through each diode, providing additional protection. This technique ensures that the surge current is divided evenly and does not overload any individual diode, thus minimizing the risk of diode destruction.

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• 18.

### To repair a damaged power supply with which you are not completely familiar, you should

• A.

Install bleeder resistors before beginning your work.

• B.

Remove the fuse before beginning your work.

• C.

Leave it alone and have a professional work on it.

• D.

Short out all the diodes before beginning your work.

C. Leave it alone and have a professional work on it.
Explanation
If you are not completely familiar with a damaged power supply, the safest option is to leave it alone and have a professional work on it. Working with a power supply that you are not familiar with can be dangerous, as there may be potential hazards or risks that you are not aware of. It is always best to seek professional help in such situations to ensure your safety and the proper repair of the power supply.

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• 19.

### If a fuse blows, and it is replaced with one having a lower current rating, there is 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.

C. The fuse will blow out right away.
Explanation
If a fuse blows and it is replaced with one having a lower current rating, there is a good chance that the fuse will blow out right away. This is because a fuse is designed to protect the circuit by blowing and breaking the circuit when the current exceeds its rating. By replacing it with a fuse of lower current rating, it will not be able to handle the current flowing through the circuit, causing it to blow out immediately.

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• 20.

### If you need exceptionally good ripple filtering for a power supply, which of the following alternatives will yield the best results?

• A.

Connect several capacitors in parallel.

• B.

Use a choke-input filter.

• C.

Connect several chokes in series.

• D.

Use two capacitor/choke filtering sections in cascade.

D. Use two capacitor/choke filtering sections in cascade.
Explanation
Connecting two capacitor/choke filtering sections in cascade will yield the best results for ripple filtering in a power supply. This is because using two sections in cascade allows for a more effective reduction of ripple voltage. The first section, typically a capacitor, filters out high-frequency noise, while the second section, typically a choke, further filters out low-frequency noise. This combination of capacitors and chokes in cascade provides a more comprehensive filtering solution, resulting in exceptionally good ripple filtering.

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Matt Balanda |BS (Aerospace Engineering) |
Physics
Matt holds a Bachelor's of Science in Aerospace Engineering and Mathematics from the University of Arizona, along with a Master's in Educational Leadership for Faith-Based Schools from California Baptist University. A devoted leader, he transitioned from Aerospace Engineering to inspire students. As the High School Vice-Principal and a skilled Physics teacher at Calvary Chapel Christian School, his passion is nurturing a love for learning and deepening students' connection with God, fostering a transformative educational journey.

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• Mar 01, 2024
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• Dec 09, 2010
Quiz Created by
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