Electromagnetic induction and generators Quiz
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5 questions, one answer each
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1. When is an e.m.f. induced in a coil near a magnet?
- A. When the magnet is still
- B. When the magnetic field through the coil is changing
- C. When the coil is not connected
- D. Only when the coil has an iron core
2. Which change would NOT increase the e.m.f. in a generator?
- A. Faster rotation
- B. A stronger magnet
- C. Fewer turns on the coil
- D. More turns on the coil
3. Lenz's law says the induced current:
- A. Always helps the movement
- B. Has the same direction as the change
- C. Is always zero
- D. Opposes the change that causes it
4. What does the frequency of an a.c. supply measure?
- A. The maximum voltage
- B. The number of cycles per second
- C. The direction of the current
- D. The number of turns on the coil
5. The coil of an a.c. generator is turned twice as fast. What happens?
- A. The frequency halves
- B. The frequency stays the same
- C. The frequency doubles and the amplitude increases
- D. The output becomes d.c.