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?
oa. its motion when it moves upward changes gravity into magnetism.
b. its motion through the magnetic field creates a current in the wire.
oc. its motion through the air transforms heat into magnetism.
od. its motion removes the magnetic field by using up the magnetic energy.

Explanation:

According to Faraday's law of electromagnetic induction, when a conductor (here, the loop of wire) moves through a magnetic field (by rotating), it cuts the magnetic field lines. This relative motion induces an electromotive force (emf) in the conductor, which in turn creates an electric current if the circuit is closed.

• Option A is incorrect because gravity and magnetism are two different fundamental forces and motion of the wire loop does not convert gravity into magnetism.
• Option C is wrong as motion through air does not transform heat into magnetism. Heat and magnetism are different forms of energy and there is no such transformation in this context.
• Option D is incorrect because the motion of the wire loop does not remove the magnetic field. The magnetic field is a property of the magnet (assuming a permanent magnet or a source of magnetic field) and is not "used up" by the motion of the wire.

Answer:

B. Its motion through the magnetic field creates a current in the wire.