Question

The north pole of a bar magnet is moved close to the north pole of another bar magnet that is suspended by a thread. How does the energy stored in the magnetic field change?
(Picture source: Next Generation Science)
(1 point)
The energy stored in the field decreases because there is no friction.
The energy stored in the field increases because the magnet moves in the direction of the field.
The energy stored in the field decreases because the magnet moves in the direction of the field.
The energy stored in the field increases because there is no friction.

Answer 1

The energy stored in the magnetic field decreases because the suspended magnet rotates so its dipole moment aligns with the external field (it moves in the direction of the field), lowering the magnetic potential energy.