Question

a handheld generator is held near a compass. when the nail is spun, the needle on the compass begins to move, providing evidence of a magnetic field changing in the device. which piece of evidence below would support the claim that whenever a magnetic field is changed, an electric field within the wire must also change?
the generator making a loud humming sound when the nail spins quickly would support this claim.
the temperature of the wire remaining the same before and after spinning would support this claim.
the nail becoming permanently magnetized after repeated spinning would support this claim.
a light bulb turning on that is connected to the end of the wire would support this claim.

Explanation:

When a magnetic field changes, an electric field is induced (Faraday's Law of Induction). A light - bulb turning on indicates a current (which is related to an electric field) in the wire. If the light - bulb turns on when the nail spins (changing the magnetic field near the compass), it shows that a changing magnetic field (due to the spinning nail) causes a change in the electric field (current in the wire to light the bulb).

• The nail becoming permanently magnetized after spinning is about magnetization, not about the relationship between changing magnetic and electric fields.
• The temperature of the wire remaining the same before and after spinning is about thermal aspects, not relevant to the magnetic - electric field relationship.
• The generator making a loud humming sound when the nail spins is about the generator's operation (maybe mechanical or other non - electric field - magnetic field induction aspects).

Answer:

A. A light bulb turning on that is connected to the end of the wire would support this claim.