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  • Question

  • 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

  • Correct Answer
  • 78 mA 

    • Inductors problems

    Search Results

    • 1. 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
    • 2. 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
    • 3. 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
    • 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 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
    • 6. 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
    • 7. 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
    • 8. When the current through an inductor decreases, the amount of energy stored in the electromagnetic field

    • Options
    • A. increases
    • B. decreases
    • C. remains the same
    • D. doubles
      • Discuss
    • 9. An inductor, a 1 kΩ resistor, and a switch are connected in series across a 6 V battery. At the instant the switch is closed, the inductor voltage is

    • Options
    • A. 0 V
    • B. 6 V
    • C. 12 V
    • D. 4 V
      • Discuss
    • 10. An inductor and a resistor are in series with a sine wave voltage source. The frequency is set so that the inductive reactance is equal to the resistance. If the frequency is increased, then

    • Options
    • A. VR ? VL
    • B. VL < VR
    • C. VL = VR
    • D. VL > VR
      • Discuss

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