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JAMB Physics 1981 Question 48

Question 48

Electromagnetic Induction

A closed coil of wire is placed near a magnet. The magnet lies along the axis of the coil. Under which of the following conditions would there be no current in the coil?

  1. A.When the coil is moved towards the stationary magnet
  2. B.When the coil is moved away from the stationary magnet
  3. C.When the coil is held stationary but the magnet is moved towards the coil
  4. D.When both the coil and the magnet are held stationary
  5. E.When the coil is held stationary but the magnet is moved away from the coil.
Show the answer and explanation

Answer: D (When both the coil and the magnet are held stationary)

Explanation

A current is induced only when the magnetic flux through the coil changes, which needs relative motion. With both still, nothing changes.