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  • Question
  • The unit for reluctance is


  • Options
  • A. tesla
  • B. At/Wb
  • C. At/m
  • D. Wb

  • Correct Answer
  • At/Wb 


  • Magnetism and Electromagnetism problems


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    • 1. The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is

    • Options
    • A. 1,000 V
    • B. 2,000 V
    • C. 31.25 V
    • D. 3,125 V
    • Discuss
    • 2. What is the flux density in a magnetic field in which the flux in 0.1 m2 is 600 µWb?

    • Options
    • A. 6,000 µT
    • B. 600 µT
    • C. 600 T
    • D. 6 T
    • Discuss
    • 3. What is the magnetomotive force (mmf) of a wire with 8 turns carrying three amperes of current?

    • Options
    • A. 2,400 At
    • B. 240 At
    • C. 24 At
    • D. 2.4 At
    • Discuss
    • 4. When the north poles of two bar magnets are brought close together, there will be

    • Options
    • A. no force
    • B. a downward force
    • C. a force of attraction
    • D. a force of repulsion
    • Discuss
    • 5. What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it?

    • Options
    • A. 18.75 At
    • B. 30 At
    • C. 300 At
    • D. 187 At
    • Discuss
    • 6. If a loop in a basic dc generator suddenly begins rotating at a faster speed, the induced voltage

    • Options
    • A. remains unchanged
    • B. reverses polarity
    • C. increases
    • D. decreases
    • Discuss
    • 7. 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
    • 8. 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
    • 9. 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
    • 10. 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


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