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  • Question

  • 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

  • Correct Answer
  • the number of turns is decreased 

    • Inductors problems

    Search Results

    • 1. 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
    • 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. 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
    • 4. A sine wave with a period of 4 ms is changing at a faster rate than a sine wave with a period of

    • Options
    • A. 0.0045 s
    • B. 2 ms
    • C. 1.5 ms
    • D. 3,000 µs
      • Discuss
    • 5. A sine wave of 15 kHz is changing at a faster rate than a sine wave with a frequency of

    • Options
    • A. 25 kHz
    • B. 12 kHz
    • C. 18 kHz
    • D. 1.3 MHz
      • Discuss
    • 6. 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
    • 7. 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
    • 8. 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
    • 9. 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
    • 10. 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

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