4.9 MAGNETS AND MAGNETIC MATERIALS
Magnets are usually made of iron or steel. They attract certain other objects towards themselves and try to cling onto them. The illustration shows a bar magnet and a horse-shoe magnet clinging onto some pins.
Magnetic materials. Magnetic materials are materials that a magnet attracts and tries to cling onto. You already know that magnets attract objects such as pins or nails, which are made of steel. So steel is a magnetic material. Try testing as many objects as you can with a strong magnet. Find out which objects are attracted. The table below shows the results obtained by the pupils in one class.
Object
/ Made from / Magnetic?knife/scissors / steel / magnetic
pencil / wood/graphite / not magnetic
pen or comb / plastic / not magnetic
needle/pin / steel / magnetic
window / glass / not magnetic
coin / metal mixture / not magnetic
iron from roof / iron / magnetic
book / paper / not magnetic
cooking pot / Iron / magnetic
saucepan / aluminium / not magnetic
copper wire / copper / not magnetic
case of cell / zinc / not magnetic
Study the table carefully. As you can see, only a few things are attracted by a magnet. Notice that metals like aluminium, zinc and copper are not magnetic. All the magnetic objects in the table are made of iron or steel. Two uncommon metals, called nickel and cobalt, are also magnetic. So the only magnetic materials are iron, nickel and cobalt. Steel is also magnetic, but steel is just a solid solution of other materials in iron.
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· 1. What are magnets usually made of?
· 2. Magnets attract magnetic materials. What does the word attract mean?
· 3. In an exam, a pupil said that conductors are magnetic and insulators are not. Explain what his mistake is.
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