Magnetic Filed Lines Around a Bar Magnet

To show the field lines place a bar magnet under a thin sheet of plastic, and sprinkle iron filings on to the top of the plastic. The iron filings will arrange themselves into strings of filings along the field lines. It is also possible to follow the path of the field lines by placing a small compass (known as a plotting compass) on the plastic in place of the iron filings. If you move the compass in the direction that its north pole is pointing, then it will follow a field line.

Bar Magnet-Force Lines

If a soft magnetic material is brought near to a magnet it will be attracted. It has had magnetism induced in it, it has become magnetised. When the magnet is taken away, the material loses its magnetism again. Note that the magnet will continue to attract the soft magnetic material even if the material is turned round. This is the opposite behaviour to two magnets, as two magnets will repel each other in certain orientations. This simple method enables you to work out whether you are holding two magnets or one magnet and one piece of soft magnetic material.