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Home Electrical Engineering Magnetism and Electromagnetism Comments

  • Question
  • An electromagnetic field exists only when there is


  • Options
  • A. an increasing current
  • B. decreasing current
  • C. voltage
  • D. current

  • Correct Answer
  • current 


  • Magnetism and Electromagnetism problems


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    • 1. The voltage induced across a certain coil is 200 mV. A 120 Ω resistor is connected to the coil terminals. The induced current is

    • Options
    • A. 1.7 mA
    • B. 16 mA
    • C. 12 mA
    • D. 120 mA
    • Discuss
    • 2. There is 900 mA of current through a wire with 40 turns. What is the reluctance of the circuit if the flux is 400 µWb?

    • Options
    • A. 14,400 At/Wb
    • B. 1,440 At/Wb
    • C. 9,000 At/Wb
    • D. 90,000 At/Wb
    • Discuss
    • 3. When a solenoid is activated, the force that moves the plunger is

    • Options
    • A. an electromagnetic field
    • B. a permanent magnetic field
    • C. varying voltage
    • D. a steady current
    • Discuss
    • 4. What is the reluctance of a material that has a length of 0.07 m, a cross-sectional area of 0.014 m2, and a permeability of 4,500 µWb/At × m?

    • Options
    • A. 1111 At/Wb
    • B. 111 At/Wb
    • C. 11 At/Wb
    • D. 1 At/Wb
    • Discuss
    • 5. When the current through the coil of an electromagnet reverses, the

    • Options
    • A. direction of the magnetic field reverses
    • B. direction of the magnetic field remains unchanged
    • C. magnetic field expands
    • D. magnetic field collapses
    • Discuss
    • 6. A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will

    • Options
    • A. increase
    • B. decrease
    • C. remain constant
    • D. be excessive
    • Discuss
    • 7. A basic one-loop dc generator is rotated at 90 rev/s. How many times each second does the dc output voltage peak (reach maximum)?

    • Options
    • A. 90
    • B. 180
    • C. 270
    • D. 360
    • Discuss
    • 8. What is the flux density when the flux is 5.5 µWb and the cross-sectional area is 6 × 10?3 m2?

    • Options
    • A. 91.7 µT
    • B. 917 µT
    • C. 91 T
    • D. 9.7 T
    • Discuss
    • 9. If the steel disk in a crankshaft position sensor has stopped with the tab in the magnet's air gap, the induced voltage

    • Options
    • A. increases
    • B. decreases
    • C. is zero
    • D. will remain constant
    • Discuss
    • 10. A 2 µF, a 4 µF, and a 10 µF capacitor are connected in series. The total capacitance is less than

    • Options
    • A. 2 µF
    • B. 4 µF
    • C. 10 µF
    • D. 1.5 µF
    • Discuss


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