What effect does moving a magnet relative to a coil have on the coil?

What effect does moving a magnet relative to a coil have on the coil?

• A. It increases the coil's resistance
• B. It decreases energy in the source
• C. It can induce an emf in the coil
• D. It has no effect on the coil

Answer: (C)

Moving a magnet relative to a coil changes the magnetic flux through the coil. This changing flux induces an electromotive force (emf) in the coil, per Faraday’s law. If the coil is part of a closed circuit, that emf drives a current; if the circuit is open, you still get a voltage but no sustained current. The coil’s resistance stays the same (unless heating or material changes occur), so the primary effect is the induction of emf due to changing magnetic flux.

Moving a magnet relative to a coil changes the magnetic flux through the coil. This changing flux induces an electromotive force (emf) in the coil, per Faraday’s law. If the coil is part of a closed circuit, that emf drives a current; if the circuit is open, you still get a voltage but no sustained current. The coil’s resistance stays the same (unless heating or material changes occur), so the primary effect is the induction of emf due to changing magnetic flux.