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  • Question
  • What is the approximate time for a complete decay of 400 mA of inductor current, when R = 10 ohms and L = 20 H?


  • Options
  • A. 10 seconds
  • B. 8 seconds
  • C. 4 seconds
  • D. 2 seconds

  • Correct Answer
  • 10 seconds 


  • Inductors problems


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    • 1. What is the permeability of machine steel?

    • Options
    • A. 1.1 x 10?4
    • B. 5.65 x 10?4
    • C. 6.9 x 10?3
    • D. 8.8 x 10?3
    • Discuss
    • 2. Electricity may be generated by a wire:

    • Options
    • A. carrying current
    • B. wrapped as a coil
    • C. that has neutral domains
    • D. passing through a flux field
    • Discuss
    • 3. Fixed transformers have:

    • Options
    • A. a center-tapped secondary
    • B. multiple windings
    • C. turns ratios that cannot be changed
    • D. a multiple-tapped secondary
    • Discuss
    • 4. If a Wheatstone bridge is balanced, a voltmeter in the center of the bridge will read:

    • Options
    • A. the same as the source voltage
    • B. half the source voltage
    • C. zero volts
    • D. twice the source voltage
    • Discuss
    • 5. What is the total resistance of a circuit when R1 (7 k Ω) is in series with a parallel combination of R2 (20 k Ω), R3 (36 k Ω), and R4 (45 k Ω)?

    • Options
    • A. 4 k Ω
    • B. 17 k Ω
    • C. 41 k Ω
    • D. 108 k Ω
    • Discuss
    • 6. Electromagnetic induction is the generation of:

    • Options
    • A. electricity from magnetism
    • B. electricity from electricity
    • C. magnetism from electricity
    • D. magnetism from magnetism
    • Discuss
    • 7. Current will cause a magnetic field in a conductor as follows:

    • Options
    • A. An ac current causes a fixed polarity magnetic field.
    • B. A dc current causes a fixed polarity magnetic field.
    • C. A dc current causes an alternating magnetic field.
    • D. An ac current causes a fixed polarity magnetic field and a dc current causes an alternating magnetic field.
    • Discuss
    • 8. 

      What is the total inductance in the given circuit?


    • Options
    • A. 160 mH
    • B. 300 mH
    • C. 900 mH
    • D. 1700 mH
    • Discuss
    • 9. With a square wave input, an RL differentiator circuit with an output across the inductor will produce what type of waveform?

    • Options
    • A. dc
    • B. short time-duration pulses
    • C. exponential-shaped pulses
    • D. only a phase shift
    • Discuss
    • 10. When a load is not connected to the secondary of a transformer:

    • Options
    • A. primary current is zero
    • B. primary current is inversely proportional to primary impedance
    • C. secondary voltage is zero
    • D. secondary voltage is proportional to primary impedance
    • Discuss


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