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Subelement ZLF
Power Supplies
Section ZLF21
Power Supplies
ZLF2101
A mains operated DC power supply
A.
converts DC from the mains into AC of the same voltage
Correct Answer
B.
converts
energy
from the mains into DC for
operating
electronic
equipment
C.
is a diode-capacitor device for measuring mains power
D.
is a diode-choked device for measuring inductance power
ZLF2101
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ZLF2102
The following unit in a DC power supply performs a rectifying operation
A.
an electrolytic capacitor
B.
a fuse
C.
a crowbar
Correct Answer
D.
a full-
wave
diode
bridge
ZLF2102
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ZLF2103
The following unit in a DC power supply performs a smoothing operation
Correct Answer
A.
an
electrolytic
capacitor
B.
a fuse
C.
a crowbar
D.
a full-wave diode bridge
ZLF2103
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ZLF2104
The following could power a solid-state 10 watt VHF transceiver
Correct Answer
A.
a 12 volt
car
battery
B.
6 penlite cells in series
C.
a 12 volt, 500 mA plug-pack
D.
a 6 volt 10 Amp-hour Gel cell.
ZLF2104
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ZLF2105
A fullwave DC power supply operates from the New Zealand AC mains. The ripple frequency is
A.
25 Hz
B.
50 Hz
C.
70 Hz
Correct Answer
D.
100
Hz
ZLF2105
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ZLF2106
The capacitor value best suited for smoothing the output of a 12 volt 1 amp DC power supply is
A.
100 pF
B.
10 nF
C.
100 nF
Correct Answer
D.
10,
000
uF
ZLF2106
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ZLF2107
The following should always be included as a standard protection device in any power supply
A.
a saturating transformer
Correct Answer
B.
a fuse in the
mains
lead
C.
a zener diode bridge limiter
D.
a fuse in the filter capacitor negative lead
ZLF2107
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ZLF2108
A halfwave DC power supply operates from the New Zealand AC mains. The ripple frequency will be
A.
25 Hz
Correct Answer
B.
50
Hz
C.
70 Hz
D.
100 Hz
ZLF2108
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ZLF2109
The output voltage of a DC power supply decreases when current is drawn from it because
A.
drawing output current causes the input mains voltage to decrease
B.
drawing output current causes the input mains frequency to decrease
Correct Answer
C.
all power
supplies
have some
internal
resistance
D.
some power is reflected back into the mains.
ZLF2109
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ZLF2110
Electrolytic capacitors are used in power supplies because
A.
they are tuned to operate at 50 Hz
B.
they have very low losses compared to other types
C.
they radiate less RF noise than other types
Correct Answer
D.
they can be obtained in
larger
values than other types
ZLF2110
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