Page 103 - Physics_Form_2
P. 103
Magnetism
2. Permanent magnets. These retain
some magnetism even after the Activity 3.2
external magnetic field is removed. Aim: To investigate the properties
Such materials include an alloy of magnets
composed of aluminium, nickel Materials: bar magnets, block of
and cobalt (Alnico), or ceramic-like wood, iron filings, water,
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material made from a mixture of iron string, compass needle,
oxides with nickel, strontium, or cobalt retort stand
(ferrites) that become magnetised in Procedure
a magnetic field. These magnets may 1. Perform the following steps:
be naturally occurring “rare earth” (a) Position the north pole of one
elements or chemical compounds. An bar magnet close to the south
example of a permanent magnet is the pole of another bar magnet.
bar magnet shown in Figure 3.5. (b) Bring the two north poles close,
then do the same with the two
south poles.
(c) Make a note of what you
observe.
(d) Spread some iron filings onto
Figure 3.5: Bar magnet a piece of paper, then hold the
north pole of a magnet near the
Properties of magnets filings without touching them.
When you closely examine a bar magnet, (e) Repeat this by bringing the
south pole close to the filings,
you see one end marked N and the other again without contact.
end marked S. Every magnet, regardless (f) Lastly, bring the centre part of
of its shape and size, has two poles. N the magnet near the filings, but
represents a North pole and S represents do not let them touch.
a South pole as shown in Figure 3.6. (g) Record your observations.
2. Tie a string around the middle of a
bar magnet and suspend it in the air
as shown in Figure 3.7.
Figure 3.6: Bar magnet showing the String
N and S poles
Bar magnet
These poles are always marked during
the process of manufacturing for easy
identification. Colouring is also used to
mark the poles as shown in Figure 3.6.
Figure 3.7
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Physics Form 2 Final.indd 97 25/10/2025 10:26
