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Magnetism by Mind Map: Magnetism
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Law of Magnetism

Like Poles Repel, Unlike Poles Attract


Found in magnetic materials


Not found in non-magnetic materials




Induced magnetism

eg. a single bar magnet can attract a iron nail hence becoming a magnet. In turn attracting another nail. When the bar magnet is removed,Both the nails fall off due to the lost of their induced magnetism.

Magnetic Materials

May Undergo Magnetisaton

Stroking, Take one permenant magnet and stroke a magnetic material lenghtwise. Stroke from end to end over 20 continuous strokes, End of the magnetised bar where the strokes end has the opposite polarity of the end of which the stroking magnets is in contact with

Using Direct Current, A steel bar is inserted into a solenoid and a direct current is made to flow through the solenoid. A strong magnetic current is produced by the solenoid leading to the steel bar becoming magnetised., When the current is switched off, the steel bar remains magnetised

May Undergo Demagnetisation

Heating, magnet must lie in an east-west direction

Hammering, magnet must lie in an east-west direction and heated till red-hot then cooled


Permanent Magnet, Steel, Hard magnetic material., Hard to magnetise but also hard to lose its magnetism, Uses, Loudspeakers, Compasses, Magnetic door catches, Refrigerator door seals

Temporary Magnet, Iron, Soft magnetic material, Easy to magnetise but loses its magnetism easily, Electromagnets, How to increase the magnetic field strength, Increasing the current that flows through the coil, Increasing the number of coils around the soft iron, Addition of a core made out of soft magnetic materials, Made from coils of insulated copper wire coiled around a soft magnetic material (iron) with current flowing through, Magnetic only when a current is flowing through the wires., Uses, Sorting out scrap metals, Audio and Video tapes, Credit, debit and ATM cards, Televisions



Discovered by the ancient Chinese in 2000BC

A magnet

2 Poles, North pole, South pole

Similar to a bar magnet

Bar magnet(1)


Bar magnet (2), North pole of 1 attracts south pole of 2, North pole of 1 repels north pole of 2

soft iron rod (magnetic material) (2), North pole of 2 can be attracted by either poles of 1

a non-magnetic material (wood) (2), 1 and 2 remain stationary


Peak strength is not at the poles but is around 0.5cm away from the poles.

Field Lines

Drawing magnetic field lines

Things required, Pencil, Paper, Compass, Bar magnet

how to..., Put the bar magnet on the sheet of paper, and trace out its shape, Make a dot at the edge of a pole, Put the end of the compass on top of the dot and make a dot at where the needle points., Repeat Steps 1-3 till the dots reach either the end of the paper or the other pole, Draw a line to connect the dots. Yay you've got your first field line :), When finished, pick another spot near the magnet and repeat steps 1-5 for more field lines


Lines start from the north pole and end at either the south pole or simply away from the north pole

The lines cannot overlap or cross each other

The lines are closer to each other in a stronger magnetic field