Magnetism and Electromagnetism problems
- 1. The component that produces power in an electromagnetic generator is called the
Options- A. armature
- B. field winding
- C. commutator
- D. brush Discuss
Correct Answer: armature
- 2. A Hall effect sensor
Options- A. exists only in theory
- B. is a noncontacting magnetic sensor
- C. can operate only a few times before failure
- D. produces very large voltages Discuss
Correct Answer: is a noncontacting magnetic sensor
- 3. What is the reluctance of a material that has a length of 0.045 m, a cross-sectional area of 0.015 m2, and a permeability of 2500 µWb/At·m?
Options- A. 833.33 µAt/Wb
- B. 0.27 At/Wb
- C. 1200 At/Wb
- D. More information is needed in order to find the reluctance. Discuss
Correct Answer: 1200 At/Wb
- 4. 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
Correct Answer: 12,000 µT
- 5. Which electromagnetic device uses brushes and a commutator?
Options- A. A speaker
- B. A dc generator
- C. A relay
- D. A solenoid Discuss
Correct Answer: A dc generator
- 6. 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
Correct Answer: is used in various sensor applications
- 7. 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
Correct Answer: All of the above
- 8. 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
Correct Answer: A solenoid
- 9. Which electromagnetic device has a flexible cone?
Options- A. A speaker
- B. A dc generator
- C. A relay
- D. A solenoid Discuss
Correct Answer: A speaker
- 10. 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
Correct Answer: 300 At
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