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  • Question
  • Which electromagnetic device has a flexible cone?


  • Options
  • A. A speaker
  • B. A dc generator
  • C. A relay
  • D. A solenoid

  • Correct Answer
  • A speaker 


  • Magnetism and Electromagnetism problems


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    • 1. Which electromagnetic device has a movable iron core called a plunger?

    • Options
    • A. A speaker
    • B. A dc generator
    • C. A relay
    • D. A solenoid
    • Discuss
    • 2. What are the effects of moving a closed wire loop through a magnetic field?

    • Options
    • A. A voltage is induced in the wire.
    • B. A current is induced in the wire.
    • C. The polarity across the wire depends on the direction of motion.
    • D. All of the above
    • Discuss
    • 3. The Hall effect

    • Options
    • A. is a phenomenon with no practical applications
    • B. is used in various sensor applications
    • C. can develop potentials of thousands of volts
    • D. is the basis for solar cell operation
    • Discuss
    • 4. Which electromagnetic device uses brushes and a commutator?

    • Options
    • A. A speaker
    • B. A dc generator
    • C. A relay
    • D. A solenoid
    • Discuss
    • 5. What is the flux density of a magnetic field whose flux is 3000 µWb and cross-sectional area is 0.25 m2?

    • Options
    • A. 12,000 µT
    • B. 83,330 T
    • C. 0 T
    • D. More information is needed in order to find flux density.
    • Discuss
    • 6. What is the magnetomotive force in a 150-turn coil of wire with 2 A flowing through it?

    • Options
    • A. 13.33 mAt
    • B. 300 At
    • C. 75 At
    • D. 152 At
    • Discuss
    • 7. What do you call the characteristic of a magnetic material whereby a change in magnetization lags the application of a magnetizing force?

    • Options
    • A. Hysteresis
    • B. Induction
    • C. Retentivity
    • D. Reluctance
    • Discuss
    • 8. The unit of flux density is known as

    • Options
    • A. magnetomotive force
    • B. a weber
    • C. a maxwell
    • D. a tesla
    • Discuss
    • 9. Which two values are plotted on a B-H curve graph?

    • Options
    • A. Reluctance and flux density
    • B. Permeability and reluctance
    • C. Magnetizing force and permeability
    • D. Flux density and magnetizing force
    • Discuss
    • 10. "Series" and "parallel" as applied to dc motors refer to

    • Options
    • A. the connection of the motor and controller
    • B. the connection of the field coil and armature windings
    • C. the connection of the brush and commutator
    • D. the connection of the motor batteries
    • Discuss


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