Electromagnetic induction Quiz
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5 questions, one answer each
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1. The flux linkage of a coil changes from 0.30 Wb (turns) to 0.10 Wb (turns) in 0.050 s. What is the average induced e.m.f.?
- A. 1.0 V
- B. 0.40 V
- C. 10 V
- D. 4.0 V
2. Which of these will NOT induce an e.m.f. in a coil?
- A. Moving a magnet towards the coil
- B. Switching off the current in a nearby coil
- C. A stationary magnet held inside the coil
- D. Rotating the coil in a magnetic field
3. A south pole is pushed towards a coil. What does Lenz's law say about the nearest end of the coil?
- A. It becomes a north pole
- B. It becomes a south pole
- C. It has no pole
- D. It alternates
4. The number of turns on a secondary coil is doubled, with everything else unchanged. What happens to the induced e.m.f.?
- A. It halves
- B. It stays the same
- C. It doubles
- D. It quadruples
5. Why does the minus sign appear in E = −d(NΦ)/dt?
- A. The e.m.f. opposes the change in flux linkage
- B. The e.m.f. is always negative
- C. Energy is lost
- D. The coil is rotating