Which change would NOT increase the emf induced in a coil by a moving magnet?
Correct answer: D. Increasing the resistance of the coil
- A. Moving the magnet faster
- B. Using a stronger magnet
- C. Increasing the number of turns on the coil
- D. Increasing the resistance of the coil
Explanation
The induced emf depends on flux, turns and speed of change, none of which is altered by the coil's resistance; resistance affects the induced current instead. The other three all raise the rate of change of flux linkage and so raise the emf. Distinguishing what changes the emf from what changes the current is exactly what this question tests.
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About Faraday's Law
Faraday's law states that an induced electromotive force equals the rate of change of magnetic flux linkage through a circuit. Questions cover changing field, area, angle or motion, the negative sign associated with Lenz's law, and the distinction between induced emf and the current that may flow in a closed circuit.
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