Which phenomenon is described by generating a current by moving magnets and changing the magnetic field around a coil?

• A. Magnetic resonance
• B. Inductive heating
• C. Electrolysis
• D. Electromagnetic induction

Answer: (D)

When the magnetic flux through a coil changes in time, an electromotive force is induced in the coil, which drives a current. This is electromagnetic induction. The induced emf is proportional to the rate of change of magnetic flux, and its direction follows Lenz’s law, meaning the induced current creates a magnetic field that opposes the change that produced it. In the described scenario, moving magnets and changing the magnetic field around the coil changes the flux, so a current is generated.

Magnetic resonance is about transitions of spin states under magnetic fields and typically involves RF radiation, not generating current in a coil. Inductive heating involves currents (often in a surrounding object) caused by changing magnetic fields but not the basic generation of current in a coil from moving magnets. Electrolysis is a chemical process driven by an external electric current, not a changing magnetic flux through a coil.