8.1Chapter 8: Magnetism and Electromagnets

The properties of magnets — Alhussan Physics - Stage 8 Revision Notes & Topical Questions

5 min read 8 parts Lesson 1 of 6 2 quizzes

📚 Alhussan Physics - Stage 8 Hub / Topical Revision

0%read

Lesson summary

Physics 8.1 The properties of magnets — Magnetic Poles, Attraction, Repulsion and Magnetic Materials — Alhussan International Academy — Physics (Stages 7–9) notes: Describe the properties of magnets, know which materials are magnetic and use domains to explain magnetic behaviour.…

Non-contact force
North-seeking pole
Magnetic elements
Compounds and alloys
Steel and lodestone
Non-magnetic

Section 1 of 8Magnets and magnetic forces

Lodestone

The Ancient Greeks found that this naturally magnetic, iron-containing rock attracted small pieces of iron.
It was first found in Magnesia in Greece.

Non-contact force

A magnetic force acts even when objects are not touching.

Poles

Every magnet has a north pole and a south pole, and the forces are strongest at the poles.

Section 2 of 8Attraction and repulsion

Poles brought together	Force
North and south (unlike)	Attract
North and north (like)	Repel
South and south (like)	Repel

Compass

A freely suspended magnet turns to point north-south because the Earth behaves like a giant bar magnet.

North-seeking pole

The end that points north.

Section 3 of 8Magnetic materials

Magnetic materials

Magnetic materials materials that are attracted to magnets.

Magnetic elements

Iron, cobalt and nickel are magnetic elements.

Compounds and alloys

Some of their alloys and oxides are also magnetic.

Steel and lodestone

Steel is magnetic because it is mainly iron, and lodestone (magnetite) contains iron oxide.

Non-magnetic

Copper, aluminium, brass, plastic, wood, glass and cotton are not magnetic.

Attraction only

A magnetic material is attracted to a magnet but is never repelled by it.
Magnetic materials do not attract or repel each other.
Only two magnets can repel each other, so repulsion is the test for a magnet.

Section 4 of 8Domains

Domains

Domains very small regions in a magnetic material, each behaving like a tiny bar magnet.

Unmagnetised

The domains point in many different directions and their effects cancel.

Magnetised

The domains line up when the material is put near a magnet or stroked with it.

Breaking a magnet

Each piece is a magnet with its own north and south pole because the domains remain.

Section 5 of 8Magnetising and demagnetising

Iron

It is easy to magnetise but loses its magnetism when the magnet is removed.

Steel

It is harder to magnetise than iron but stays magnetised, making a permanent magnet.

Stroking

Stroking a steel needle repeatedly in the same direction with a magnet makes a stronger magnet.

Demagnetising

A permanent magnet cannot be turned off but can be demagnetised.
Heating it to a high temperature jolts the domains into random directions.
Hitting it with a hammer or dropping it does the same.

Section 6 of 8Everyday uses

Credit card strip

A plastic containing tiny iron pieces that behave like magnets stores information.

Other uses

Fridge door seals, compasses, loudspeakers, motors and magnetic catches.

Magnetic levitation

This happens when like poles repel.

Test	Result for a magnet	Result for unmagnetised iron
Near one pole of a known magnet	Attracts or repels	Attracts only

Section 7 of 8Key terms

Term	Meaning
Magnetic field	The region around a magnet where magnetic materials experience a force.
Pole	The end of a magnet where the magnetic force is strongest.
Domain	A tiny region in a magnetic material that acts like a small magnet.
Magnetic material	A material attracted by a magnet, such as iron, cobalt or nickel.
Permanent magnet	A magnet that stays magnetised.
Demagnetise	To remove the magnetism of a magnet.