Gibilisco - Power Supplies
- 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.
- 2.Which of the following components is not necessarily required in a power supply designed toproduce 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.
- 3.Of the following appliances, which would need the biggest transformer?
- A.
A clock radio
- B.
A television broadcast transmitter
- C.
A shortwave radio receiver
- D.
A home television set
- 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.
- 5.In a power supply designed to provide high power at low voltage, the best rectifier circuitwould probably be the
- A.
Half-wave arrangement.
- B.
Full-wave, center-tap arrangement.
- C.
Quarter-wave arrangement.
- D.
Voltage doubler arrangement.
- 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 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.
- 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.
- 9.What is the principal disadvantage of a voltage-doubler power supply circuit?
- A.
Excessive current
- B.
Excessive voltage
- C.
Insufficient rectification
- D.
Poor regulation under heavy loads
- 10.Suppose a transformer secondary provides 10-V rms ac to a voltage-doubler circuit. What isthe approximate dc output voltage with no load?
- 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.
1⁄4 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.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.
- 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.
- 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.
- 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.
- 17.In order to minimize the risk of diode destruction as a result of surge currents that can occurwhen a power supply is first switched on, which of the following techniques can be useful?
- A.
Connecting multiple diodes in parallel, with low-value resistors in series with each diode
- B.
Connecting multiple diodes in parallel, with low-value capacitors in series with each diode
- C.
Connecting multiple diodes in series, with low-value chokes across each diode
- D.
Connecting multiple diodes in series, with low-value resistors across each diode
- 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.
- 19.If a fuse blows, and it is replaced with one having a lower current rating, there is a goodchance 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.
- 20.If you need exceptionally good ripple filtering for a power supply, which of the followingalternatives 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.
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