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Magnetism and Electromagnetism (Electronics) Question and Answers-Page first

# Magnetism and Electromagnetism problems

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• 1. The component that produces power in an electromagnetic generator is called the

• Options
• A. armature
• B. field winding
• C. commutator
• D. brush

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• 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

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• 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.

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• 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.

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• 5. Which electromagnetic device uses brushes and a commutator?

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

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• 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

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• 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

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• 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

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• 9. Which electromagnetic device has a flexible cone?

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

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• 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

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