Poles, Magnetic Fields and Magnetic Materials

Magnetism is one of the fundamental forces in nature. In this opening lesson of the AQA GCSE Combined Science Trilogy (8464) Magnetism and Electromagnetism topic, you will learn about magnetic poles, magnetic fields, field lines and magnetic materials. This content maps to specification section 6.7.1 — Permanent and induced magnetism, magnetic forces and fields.

What Is a Magnet?

A magnet is an object that produces a magnetic field around itself. The magnetic field is a region of space where a force acts on other magnets or on magnetic materials.

Magnetic Materials

Only certain materials are attracted to magnets. These are called magnetic materials (also known as ferromagnetic materials). At GCSE level you need to know four:

Magnetic Materials	Non-Magnetic Materials
Iron	Wood
Steel (contains iron)	Plastic
Cobalt	Copper
Nickel	Aluminium

Exam Tip: A very common mistake is to say "all metals are magnetic". This is wrong — copper, aluminium and gold are metals but they are NOT magnetic. Only iron, steel, cobalt and nickel are magnetic at GCSE level. AQA frequently tests this.

Magnetic Poles

Every magnet has two poles: a north-seeking pole (N) and a south-seeking pole (S). The magnetic field is strongest at the poles.

Rules of Magnetic Interaction

Like poles repel — N repels N, S repels S.
Unlike poles attract — N attracts S, S attracts N.

Pole Combination	Result
N — N	Repel
S — S	Repel
N — S	Attract
S — N	Attract

Exam Tip: "Like poles repel, unlike poles attract" is one of the most frequently examined facts in magnetism. If a question asks what happens when two magnets are brought together, identify the facing poles first.

Magnetic Fields

A magnetic field is the region around a magnet where a force acts on another magnet or on a magnetic material. We cannot see magnetic fields, but we represent them using magnetic field lines (also called lines of force).

Properties of Magnetic Field Lines

Field lines always point from north to south (outside the magnet).
Field lines never cross each other.
The closer together the field lines, the stronger the magnetic field.
The field is strongest at the poles, where lines are most concentrated.

graph LR
    subgraph "Bar Magnet — Field Line Pattern"
        N["N pole"] -->|"Field lines travel from N to S outside the magnet"| S["S pole"]
    end
    style N fill:#ff6666,stroke:#cc0000
    style S fill:#6666ff,stroke:#0000cc

Uniform and Non-Uniform Fields

Field Type	Description	Field Lines
Non-uniform	Field strength varies (e.g. around a bar magnet)	Curved, variable spacing
Uniform	Field strength is the same everywhere in the region	Parallel, equally spaced

A uniform field can be created between two flat, parallel magnets with opposite poles facing each other. The field lines are straight, parallel and evenly spaced in the gap between them.

The Magnetic Field of the Earth

The Earth has its own magnetic field, which behaves as if there were a giant bar magnet inside it.

Key facts:

The magnetic north pole of the Earth is actually near the geographic south pole, and vice versa.
A compass needle (a small bar magnet) aligns with the Earth's field — its north-seeking pole points towards geographic north.
The Earth's magnetic field protects the planet from charged particles in the solar wind.

graph TD
    subgraph "Earth's Magnetic Field"
        GN["Geographic North"] --- MS["Magnetic South Pole (near geographic north)"]
        GS["Geographic South"] --- MN["Magnetic North Pole (near geographic south)"]
        MN -->|"Field lines curve from magnetic N to magnetic S"| MS
    end

Exam Tip: This is confusing but important: a compass needle's north pole points towards geographic north. Since unlike poles attract, the magnetic south pole of the Earth must be near the geographic north pole. AQA has tested this before — make sure you can explain it clearly.

Common Mistakes

Mistake	Correction
"All metals are magnetic"	Only iron, steel, cobalt and nickel are magnetic
"Magnets attract everything"	Magnets only attract magnetic materials and other magnets
"Field lines start and stop"	Field lines form continuous loops (they continue inside the magnet from S to N)
"The Earth's magnetic north pole is at geographic north"	The magnetic south pole is near geographic north

Worked Example

Q: A bar magnet is placed on a table. A small iron nail is placed 5 cm from the north pole. Explain why the nail moves towards the magnet.

A: The iron nail is a magnetic material. When placed in the magnetic field of the bar magnet, the nail becomes an induced magnet. The end of the nail nearest the north pole of the bar magnet becomes an induced south pole (unlike poles attract), so the nail is attracted towards the north pole of the magnet. The force of attraction causes the nail to accelerate towards the magnet.

Summary

Magnets have a north pole and a south pole; the field is strongest at the poles.
Like poles repel; unlike poles attract.
A magnetic field is the region around a magnet where a force acts on magnetic materials or other magnets.
Field lines go from N to S outside the magnet, never cross, and are closer together where the field is stronger.
Only iron, steel, cobalt and nickel are magnetic at GCSE level.
The Earth has a magnetic field; the magnetic south pole is near geographic north.

Exam Tip (AQA 8464): You should be able to draw the field pattern around a bar magnet from memory. Practise sketching it — smooth curves from N to S, with arrows, and closer together at the poles.