A magnet attracts some materials like iron filings, and do no attract others like plastic materials.

Magnets are named according to their shapes; for example, the bar magnet, the horse-shoe magnet and the loudspeaker magnet.

MAGNETIC POLES

           These are the two points on a magnet where the magnetic force seems to concentrate. When a magnet is dipped into iron filings, the filings cling more around the poles.

The two magnetic poles are the North Pole and the South Pole and can be defined by suspending a bar magnet at its centre using a thread.

• The North Pole or the north-seeking pole is the pole which is always pointing towards the north of the earth when a bar magnet is suspended freely at its centre.
• On the other hand, the South pole or the south-seeking pole is the pole which is always pointing towards the south of the earth when a bar magnet is suspended freely at its centre.

Two similar magnetic poles always repel each other, while two opposite magnetic poles always attract each other. This is illustrated in figure below;

An experiment to determine the polarity of a magnet

• A magnet of known polarity is suspended and the unknown pole is brought closed to the North Pole, then to the South Pole of the suspended magnet.
• If repulsion occurs with the North Pole, then the unknown pole is a North Pole. (Like poles repel)

Likewise if repulsion occurs with the South Pole, then the unknown pole is a south pole.

• Attraction is inconclusive because with · attraction, the material with unknown pole can either be a magnet or a magnetic material. So repulsion is the only true test for polarity.