13. MAGNETISM
Key notes:
1. The poles of a magnet are the parts of a magnet where the magnetic force is
strongest.
2. The pole of the magnet that points north is known as the N-pole, while the
other pole of the magnet is the S-pole.
3. Like poles repels, unlike poles attract.
4. The repulsion between like poles is used to determine the polarity of a magnet.
5. Induced magnetism is the magnetism acquired by an unmagnetised magnetic
material when it is close to or in contact with a permanent magnet.
6. A steel bar is magnetized by placing it inside a solenoid carrying a direct
current.
7. The poles of the magnet produced can be determined using the right-hand grip
rule.
8. A magnet becomes weaker if:
a) It is stored without its soft-iron keepers.
b) It is dropped or heated.
9. A magnet is demagnetized by placing it inside a solenoid carrying an
alternating current and then withdrawing it far away from the solenoid.
10. A magnetic field is the region in space where a magnetic force is exerted.
11. The magnetic field pattern around a magnet can be plotted using a plotting
compass or iron fillings.
12. The magnetic lines of force point away from a N-pole and towards a S-pole.
13. At a neutral point, the resultant magnetic force is zero.
14. Soft iron is easily magnetized strongly but the induced magnetism is only
temporary.
15. Steel is more difficult to demagnetize but the induced magnetism is
permanent.
16. Electromagnets are made by winding a coil of insulated copper wire around a
soft iron core.
17. An electromagnet loses its magnetism when the current is switched off.
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