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Inductors problems

  • 1. A sine wave voltage is applied across an inductor. When the frequency of the voltage is decreased, the current

  • Options
  • A. is increased
  • B. is decreased
  • C. does not change
  • D. momentarily goes to zero
    • Discuss
  • 2. A 320 µH coil is in series with a 3.3 kΩ resistor. How long does it take for current to build up to its full value?

  • Options
  • A. 0.48 s
  • B. 0.48 ms
  • C. 0.48 µs
  • D. 48 s
    • Discuss
  • 3. Two 10 H inductors are in parallel and the parallel combination is in series with a third 10 H inductor. What is the approximate total reactance when a voltage with a frequency of 7 kHz is applied across the circuit terminals?

  • Options
  • A. 219 kΩ
  • B. 66 kΩ
  • C. 660 kΩ
  • D. 1.3 MΩ
    • Discuss
  • 4. The inductance of an iron-core coil decreases if

  • Options
  • A. the number of turns is decreased
  • B. the iron core is removed
  • C. the length of the coil decreases
  • D. none of the above
    • Discuss
  • 5. Two inductors, L1 and L2, are in parallel. L1 has a value of 25 µH and L2 a value of 50 µH. The parallel combination is in series with L3, a 20 µH coil. The entire combination is across an ac source of 60 Vrms at 300 kHz. The total rms current is

  • Options
  • A. 87 mA
  • B. 870 mA
  • C. 87 A
  • D. 337 mA
    • Discuss
  • 6. Three 15 mH inductors are in series. The total inductance is

  • Options
  • A. 15 mH
  • B. 30 mH
  • C. 45 mH
  • D. 5 mH
    • Discuss
  • 7. The following coils are in parallel: 75 µH, 40 µH, 25 µH, and 15 µH. The total inductance is approximately

  • Options
  • A. 6.9 µH
  • B. 14 µH
  • C. 2.2 µH
  • D. 155 µH
    • Discuss
  • 8. A switch, a 220 Ω resistor, and a 60 mH inductor are in series across a 20 V battery. What is the current through the inductor two time constants after the switch is closed?

  • Options
  • A. 91 mA
  • B. 78 mA
  • C. 57 mA
  • D. 400 mA
    • Discuss
  • 9. An 18 V power supply is connected across a coil with a winding resistance of 180 Ω. Current flow in the coil is

  • Options
  • A. 1 mA
  • B. 10 mA
  • C. 100 mA
  • D. 1 A
    • Discuss
  • 10. A 5 mH, a 4.3 mH, and a 0.6 mH inductor are connected in parallel. The total inductance is

  • Options
  • A. 9.9 mH
  • B. greater than 5 mH
  • C. 9.9 mH or greater than 5 mH
  • D. less than 0.6 mH
    • Discuss

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