Question

In a simple electric generator, a conducting loop of wire is placed in a magnetic field. The loop of wire is then rotated. Why is it necessary for the wire to be rotated?
A.
Its motion removes the magnetic field by using up the magnetic energy.
B.
Its motion when it moves upward changes gravity into magnetism.
C.
Its motion through the air transforms heat into magnetism.
D.
Its motion through the magnetic field creates a current in the wir

Answer 1

D.

Rotating the loop moves the conductor through the magnetic field so the charges in the wire experience a magnetic force (q v × B). That produces an emf (motional emf) and—if the circuit is closed—a current. Equivalently, rotation changes the magnetic flux through the loop and Faraday’s law says a changing flux induces an emf.