Answer:

a) When the north magnetic pole moves, the magnetic field lines move. Magnetic field lines are also called magnetic force lines.

Activity:

Compass and bar magnet, please.

Attach the bar magnet to the drawing board with glue.

The magnet’s edge should be noted.

The compass should be near the magnet’s north pole. The needle’s south pole points to the magnet’s north pole.

Mark the needle ends.

Moving the needle reveals that the south pole occupies the north pole.

A smooth curve is formed by combining the points.

b) A free-floating magnet points north-south because the earth is a magnet with its south pole in the north and its north pole in the south.