Joan makes the device shown in her science class. what would happen to the magnetic field if she connects the battery in the opposite direction? a) the field would stop. b) the field would get stronger. c) the field would reverse its poles. d) the field would get weaker.

the answer is C) The field would reverse its poles.

C) The field would reverse its poles.

Explanation:

The given diagram shows an electromagnet. A iron nail is placed between coil through which current is passes as it is connected to the battery.

When the terminals are reversed, the current still flows but in the opposite direction. Magnetic field is still generated but with the reversed poles.  

Magnetic field produced:

B = μ n I

The direction of the magnetic field reverses with the direction of the current.

c.the charges if the proton and electron and gravity

thermal energy is the answer