Questions - Power Supplies

Question file 21


                                                                                        QUESTIONS WITH ANSWERS
  1. A mains operated DC power supply:                                                 STUDY NOTES 
    1. converts DC from the mains into AC of the same voltage    
    2. converts energy from the mains into DC for operating electronic equipment
    3. is a diode-capacitor device for measuring mains power
    4. is a diode-choked device for measuring inductance power
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  2. The following unit in a DC power supply performs a rectifying operation:
    1. an electrolytic capacitor
    2. a fuse
    3. a crowbar
    4. a full-wave diode bridge
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  3. The following unit in a DC power supply performs a smoothing operation:
    1. an electrolytic capacitor
    2. a fuse
    3. a crowbar
    4. a full-wave diode bridge
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  4. The following could power a solid-state 10 watt VHF transceiver:
    1. a 12 volt car battery
    2. 6 penlite cells in series
    3. a 12 volt, 500 mA plug-pack
    4. a 6 volt 10 Amp-hour Gel cell.
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  5. A fullwave DC power supply operates from the New Zealand AC mains. The ripple frequency is:
    1. 25 Hz
    2. 50 Hz
    3. 70 Hz
    4. 100 Hz
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  6. The capacitor value best suited for filtering the output of a 12 volt 1 amp DC power supply is:
    1. 100 pF
    2. 10 nF
    3. 100 nF
    4. 10,000 uF
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  7. The following should always be included as a standard protection device in any power supply:
    1. a saturating transformer
    2. a fuse in the mains lead
    3. a zener diode bridge limiter
    4. a fuse in the filter capacitor negative lead
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  8. A halfwave DC power supply operates from the New Zealand AC mains. The ripple frequency will be:
    1. 25 Hz
    2. 50 Hz
    3. 70 Hz
    4. 100 Hz
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  9. The output voltage of a DC power supply decreases when current is drawn from it because:
    1. drawing output current causes the input mains voltage to decrease
    2. drawing output current causes the input mains frequency to decrease
    3. all power supplies have some internal resistance
    4. some power is reflected back into the mains.
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  10. Electrolytic capacitors are used in power supplies because:
    1. they are tuned to operate at 50 Hz
    2. they have very low losses compared to other types
    3. they radiate less RF noise than other types
    4. they can be obtained in larger values than other types
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