Final answer:
The compass must be swung around a planar magnet, resulting in four complete revolutions, indicating that the magnet has two poles: a north and a south pole.
Step-by-step explanation:
When a compass is moved in a circular plane around a planar magnet and makes four complete revolutions, it is interacting with the magnetic field lines created by the magnet. The needle of the compass aligns itself with these magnetic field lines at each point in its path. For the compass to complete four full rotations, the magnet must have two poles: a north and a south pole.
Magnetic fields extend from the north pole of a magnet to the south pole, creating a closed-loop pattern. As the compass is moved around the magnet, the needle rotates to continuously align with the nearest pole. Hence, with each pass around the two poles, the compass needle would make one full rotation. Therefore, completing four rotations indicates the presence of a single pair of north and south poles on the magnet.