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139 lines
2.3 KiB
Plaintext
139 lines
2.3 KiB
Plaintext
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% FILENAME = N21.TXT
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% Power Supplies
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% Release version 2, January 2000
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% Q 6 corrected 6 Mar 2012
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%Question: 1
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#21.1 A mains operated DC power supply:
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converts DC from the mains into AC of the same voltage
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converts energy from the mains into DC for operating electronic equipment
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is a diode-capacitor device for measuring mains power
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is a diode-choked device for measuring inductance power
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% ans 2
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%Question: 2
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#21.2 The following unit in a DC power supply performs a rectifying operation:
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an electrolytic capacitor
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a fuse
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a crowbar
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a full-wave diode bridge
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% ans 4
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%Question: 3
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#21.3 The following unit in a DC power supply performs a smoothing operation:
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an electrolytic capacitor
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a fuse
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a crowbar
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a full-wave diode bridge
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% ans 1
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%Question: 4
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#21.4 The following could power a solid-state 10 watt VHF transceiver:
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a 12 volt car battery
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6 penlite cells in series
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a 12 volt, 500 mA plug-pack
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a 6 volt 10 Amp-hour Gel cell.
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% ans 1
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%Question: 5
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#21.5 A fullwave DC power supply operates from the New Zealand AC mains. The ripple
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frequency is:
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25 Hz
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50 Hz
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70 Hz
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100 Hz
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% ans 4
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%Question: 6
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#21.6 The capacitor value best suited for smoothing the output of a 12 volt 1 amp DC power supply is:
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100 pF
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10 nF
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100 nF
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10,000 uF
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% ans 4
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%Question: 7
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#21.7 The following should always be included as a standard protection device in any power
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supply:
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a saturating transformer
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a fuse in the mains lead
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a zener diode bridge limiter
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a fuse in the filter capacitor negative lead
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% ans 2
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%Question: 8
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#21.8 A halfwave DC power supply operates from the New Zealand AC mains. The ripple
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frequency will be:
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25 Hz
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50 Hz
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70 Hz
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100 Hz
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% ans 2
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%Question: 9
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#21.9 The output voltage of a DC power supply decreases when current is drawn from it because:
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drawing output current causes the input mains voltage to decrease
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drawing output current causes the input mains frequency to decrease
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all power supplies have some internal resistance
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some power is reflected back into the mains.
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% ans 3
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%Question: 10
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#21.10 Electrolytic capacitors are used in power supplies because:
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they are tuned to operate at 50 Hz
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they have very low losses compared to other types
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they radiate less RF noise than other types
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they can be obtained in larger values than other types
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% ans 4
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