6.1.3Magnetism and Electromagnetism

Permanent and Induced Magnets — Edexcel International GCSE Science Double Award 4SD0 - Physics Revision Notes & Topical Questions

5 min read 9 parts Lesson 4 of 10

📚 Edexcel International GCSE Science Double Award 4SD0 - Physics Hub / Topical Revision

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Part 1 of 7Permanent magnets

A permanent magnet keeps its magnetism and has its own magnetic field at all times.

Permanent magnets

It is made from a magnetically hard material such as steel or an alloy of iron, nickel and cobalt.

Permanent magnets can both attract and repel,

and they are used wherever a magnetic field is needed without a power supply, for example in compasses and fridge doors.

Part 2 of 7Induced magnets

An induced magnet is a piece of magnetic material that becomes a magnet only while it is in a magnetic field.

A piece of soft iron brought close to a permanent magnet's north pole has a south pole induced at the near end and a north pole at the far end.

Attractive

Because the end nearest the magnet is the opposite pole, the force is always attractive.

This is why a magnet can pick up paper clips and nails and why an unmagnetised piece of iron is always attracted, never repelled.

When the permanent magnet is removed, soft iron loses nearly all of its magnetism straight away; a steel object keeps much of it.

Part 3 of 7Making a magnet

Stroking

Stroking stroke a steel bar many times, in the same direction only, with one pole of a permanent magnet. The domains line up.

Using a solenoid

Using a solenoid place a steel bar in a coil carrying direct current.

The field of the coil lines up the domains.
The poles can be predicted from the current direction (see 6.1.8).

In the Earth's field

In the Earth's field a steel bar tapped while aligned north-south gains a weak magnetism.

Part 4 of 7Demagnetising

Heating

Heating to a high temperature, or hammering, shakes the domains into random directions.

Alternating current

Placing the magnet in a solenoid carrying alternating current and slowly withdrawing it,

so the field decays gradually, leaves the domains in random directions.

Storing bar magnets in pairs with unlike poles together, joined by iron 'keepers', helps keep the domains aligned.

Part 5 of 7Comparing the two

Permanent	Induced
Has its own field at all times	Magnetic only while in another field
Can attract or repel	Only attracts
Hard magnetic material	Usually soft magnetic material
Example: bar magnet	Example: iron nail near a magnet

Part 6 of 7Why induced magnets are always attracted

The ends of an iron bar placed in a field become poles opposite to the nearest pole of the magnet.

Both ends feel a force, the near end is attracted and the far end is repelled,

but since the near end is closer to the magnet it feels a bigger force than the far end does.

The net force is therefore attraction, whichever pole is used.

If you reverse the magnet, the polarity of the induced poles also reverses, and the attraction remains.

This is why a nail jumps up to either pole.

A chain of paper clips hanging from a magnet shows the same idea: each clip induces a pole in the next. When the magnet is pulled away, the soft iron clips lose their magnetism and fall apart.

Uses of permanent and induced magnets

Hard magnetic alloys are used in loudspeakers, electric motors and magnetic catches because they do not demagnetise.

Why induced magnets are always attracted

Soft iron is used in transformer cores and electromagnets, where rapid magnetising and demagnetising is needed.

A magnetic strip on a card uses tiny regions of hard magnetic material magnetised in patterns to store data; keeping the card near a strong magnet can scramble this information.

Checking your understanding

Suppose a bar is brought up to a compass needle.

Why induced magnets are always attracted

If one end of the needle is repelled, the bar must be a magnet; if both ends of the needle are attracted equally, the bar is probably unmagnetised iron.

A further test is to bring the bar close to a pile of iron filings: a magnet picks up filings mostly at its poles,

while an unmagnetised bar picks up none.

These tests show the difference between a magnet and a magnetic material, and apply the rule that only repulsion is a conclusive test.

Part 7 of 7Worked examples

A paper clip is held near the north pole of a magnet. State the pole induced at the end of the clip nearest the magnet and explain why the clip is attracted.
A steel needle is to be magnetised. Describe a method and say how the pole produced at the end depends on the method.

Key terms

Term	Meaning
Permanent magnet	A magnet that keeps its magnetism.
Induced magnet	Material that is magnetic only while it is in another magnetic field.
Demagnetise	Remove the magnetism by disordering the domains.
Keeper	Piece of iron placed across the poles of stored magnets.

Avoid these mistakes

Saying induced magnets are repelled. They are always attracted.

Stroking back and forth, which cancels the alignment.

Thinking that heating a magnet strengthens it.

Mixing up iron and steeliron is soft, steel is hard.

Last updated: 20 October 2026