Question

Joan makes the device shown in her science class.

An illustration with a battery and ends labeled positive and negative. A wire is connected to the positive end of the battery and curls around an iron nail and connects back with the negative side of the battery.

What would happen to the magnetic field if she connects the battery in the opposite direction?

The field would stop.
The field would get stronger.
The field would reverse its poles.
The field would get weaker.

Answer 1

The field would reverse its poles.

Reversing the battery reverses the current direction through the coil, which reverses the electromagnet's polarity (north and south poles swap).