Questions Without Answers For Power Supplies

Question File Number 21



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


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Compiled Sun Nov 28 2010 at 8:42:55pm


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