The net force on a compass needle is zero because its north and south poles are pulled in opposite directions with equal forces in the earth's magnetic field. Second, a pair of equal torques act on the filing whenever it is not parallel to the magnetic field lines. These torques rotate the filings into alignment with the field lines like little compass needles. If we had to paint either an N or an S on the wooden pole near the north geographical pole, we should paint an S, which is the magnetic pole that attracts the N pole of a compass. Similarly, we should paint an N on the wooden pole erected in the southern hemisphere, for that is the pole that attracts the S pole of a magnetic compass.
Cans contain iron.
Domains in the can tend to line up with the earth's magnetic field. When the cans are left stationary for several days, the cans become magnetized by induction, aligning with the earth's magnetic field. A compass does no turnaround when crossing the equator. 2O. Magnetic fields deflect moving electrons in their paths. A magnet held in front of a TV picture deflects the electron beam from its intended path and distorts the picture.