A simple compass

• After a while, the bar magnet orients itself in a very specific direction.
• If you push the magnet, it turns back to its original position.
• If you come close to it with another magnet, the floating magnet can be directed as if by magic.

Place the bar magnet on the polystyrene disk and place both on the surface of the water.

• Bowl with water,
• Styrofoam disk (e.g. from cheese packages in supermarkets),
• bar magnet,
• another magnet, e.g. a strong adhesive magnet from a magnetic board or a magnetic door lock (not shown),

There should be no other magnets or iron objects in the vicinity during the first part of the experiment. The bowl must be large enough so that the bar magnet can align itself without hitting the edge of the bowl. The polystyrene disk must be large or thick enough so that the bar magnet does not sink. The experiment should ideally be carried out on the floor to provide more space and observation possibilities.

What is technically behind the experiment

The floating magnet adjusts itself in a north-south direction just like a compass needle. The red end of the magnet points north. (There is a magnetic south pole at the geographic north pole.) Sailors of the 12th/13th century were already familiar with a similar type of "compass", which consisted of a magnetic stone on a wooden float and a bowl of water. As in this student's experiment, this magnetic stone was set on its float in a north-south direction. Directing the floating magnet with another magnet illustrates the long-distance effect of magnetic fields.

What the experiment has to do with everyday life

Almost all magnetic compasses that are still used on sailing and motor boats today are based on the same construction principle.

Carolin Sippel