Question

joan makes the device shown in her science class. diagram: iron nail, coiled wire, wire, battery (labeled with - and +). 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.

Explanation:

The device is an electromagnet (formed by a coiled wire around an iron nail connected to a battery). The direction of the magnetic field in an electromagnet depends on the direction of the electric current. Reversing the battery connection reverses the current direction. By the right - hand rule (or principles of electromagnetism), reversing the current reverses the polarity of the magnetic field. The strength of the magnetic field depends on factors like current magnitude, number of coils, etc., not just the direction of the current. So reversing the battery direction (and thus current direction) will reverse the poles of the magnetic field, not stop it, make it stronger or weaker.

Answer:

The field would reverse its poles.