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Magnetism is an invisible force

that attracts or repels some

materials, such as iron and steel,

but not others, like plastic and

silver. In a magnetic material, the

atoms line up in groups or regions

called. MAGNETIC DOMAINS.

HOW CAN A MAGNETIC FIELD BE SEEN?

If iron filings are sprinkled around a magnet, they will

line up along the lines of force of its magnetic field.

The pattern made by the filings always shows the

lines of force looping outwards between the magnet’s

north and south poles. The magnetic field gets weaker

as it gets farther away from the magnet.

Every atom in a piece of iron is a tiny, permanent magnet. These

tiny magnets group together in magnetic regions called domains.

If the north-south magnetic poles of these domains all point in

different directions, they cancel each other’s magnetism out.

WHAT ARE MAGNETIC MATERIALS?

The elements iron, nickel, and cobalt are magnetic

materials – they can be magnetized by another

magnet. But in their pure form, they easily lose their

magnetism by heat or hammering. Permanent magnets

are made from mixtures of these elements with others,

such as steel (iron and carbon), for example.

WHAT MAKES A PERMANENT MAGNET?

In a permanent magnet, the magnetic poles of the

domains point in the same direction, so their magnetic

fields reinforce one another. Magnetic material can be

magnetized by stroking it with a magnet to line up

the domains. Heat or hammering shakes the domains

out of position, and the material loses its magnetism.

HOW DOES A MAGNETIC COMPASS WORK?

The Earth's core acts as a gigantic magnet with a vast

. MAGNETIC FIELD. In a magnetic compass, the
northern end of the compass needle always points in
the direction of the Earth’s north magnetic pole.
Its other (southern) end always points south.

WHAT ARE MAGNETIC POLES?

Every magnet has a north magnetic pole and a

south magnetic pole. These are the places where the

magnetic force is strongest. The laws of magnetism

are that like (the same) poles repel each other, and

unlike (opposite) poles attract each other.

A magnet creates a force in the space

around it. The area in which the force

operates is the magnetic field. A magnetic

field can be imagined as lines of force that

spread out from the magnet’s poles.

1 MAGNETIC EARTH

The Earth’s magnetic poles attract particles from the Sun that glow

when they reach the atmosphere. The Earth’s magnetic north and south

poles are close to its geographical North and South Poles.

MAGNETIC DOMAINS

4 MAGNETIC POWER

To keep a magnet strong, place a

keeper between its poles when

it is not in use. A keeper is a

piece of soft iron. The poles

magnetize the keeper, which in

turn keeps the poles’ domains

pointing in the same direction.

MAGNETIC POLES 1

Iron filings can be used to show the repulsion

between two like poles, and the attraction between unlike poles.

Magnetism

MAGNETIC FIELD

Iron filings show how two like

poles repel each other’s fields

Magnetic

domains

are lined up in

the two poles

Filings show the attraction

between unlike poles

Horseshoe

magnet

North pole

North pole South pole

North pole

Keeper

Keeper

FIND OUT MORE. Atoms 157 • Electromagnetism 186 • Elements 160–161

183

hese

e.

magnetism