You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
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.
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.
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.
Every magnet has two poles: a north-seeking pole (N) and a south-seeking pole (S). The magnetic field is strongest at the poles.
| 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.
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).
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
| 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 Earth has its own magnetic field, which behaves as if there were a giant bar magnet inside it.
Key facts:
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.
| 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 |
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.
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.
Magnetic field lines are an imaginary model used to represent the direction and strength of a magnetic field. They are not real physical objects — they are a visualisation tool. Understanding the rules governing field lines is essential for drawing accurate patterns in the exam.
A compass placed at any point on a field line will align its north-seeking pole with the direction of the field. This is why arrows on field lines point from N to S outside the magnet: a small compass placed in that region would rotate so that its N pole points that way.
Although we draw arrows pointing from N to S outside the magnet, the loops actually continue inside the magnet from S back to N. This means every field line forms a complete closed loop — it never begins or ends in empty space. At GCSE you usually only draw the external portion of the loop.
The closer together the field lines, the stronger the magnetic field at that point. Where lines are widely spaced, the field is weak. This is why the region near the poles shows lines packed tightly together, while lines drawn further away are more spread out.
If two field lines crossed, it would mean a compass at that point would have to align in two different directions simultaneously — which is impossible. This is a quick sanity check when sketching field patterns in the exam: if any lines cross, the diagram is wrong.
Q: A diagram shows a bar magnet with field lines. At point X the field lines are tightly packed; at point Y the lines are widely spaced. Compare the magnetic field strength at X and Y, and state what would happen if a small piece of iron were placed at each point.
A: At point X, the field is stronger because the field lines are more densely packed. At point Y, the field is weaker because the lines are further apart. If an iron nail were placed at point X, it would become an induced magnet with a stronger attraction towards the bar magnet than if the same nail were placed at point Y. The force on the iron at Y would still exist, but be smaller in magnitude.
Q: A student places a plotting compass at four positions around a bar magnet: directly to the east of the N pole, directly to the east of the S pole, halfway between N and S on the outside, and at a point far from the magnet. Describe how the compass needle points in each case.
A:
| Position around a bar magnet | Field strength | Line spacing |
|---|---|---|
| At the pole (very close) | Very strong | Lines very close together |
| 1 cm from the pole | Strong | Lines close together |
| 5 cm from the pole (side) | Weak | Lines widely spaced |
| Far from the magnet | Negligible | Effectively no lines drawn |
A useful comparison to deepen understanding:
| Force Type | Acts on | Range | Direction |
|---|---|---|---|
| Magnetic | Magnets and magnetic materials only | Short range (decreases rapidly with distance) | Along field lines |
| Gravitational | All masses | Long range | Always attractive towards centre of mass |
| Electrostatic | Charged objects | Varies with distance | Attractive or repulsive depending on charge |
Magnetism is therefore selective (only acts on certain materials) and short-range, unlike gravity which acts on everything.
A frequent confusion: if a compass N-seeking pole points towards geographic north, and unlike poles attract, then the Earth's magnetic pole near geographic north must be a magnetic south pole. Many students find this counter-intuitive and instinctively say the Earth has a magnetic N pole near geographic N. In an exam answer, always work from the rule of attraction to deduce the pole type.
graph TD
Start["Two magnets approached"] --> Check{"Which poles face?"}
Check -->|"N facing N"| Rep["REPEL — field lines curve away, neutral point between"]
Check -->|"S facing S"| Rep
Check -->|"N facing S"| Att["ATTRACT — uniform field in gap"]
Check -->|"S facing N"| Att
Grades 3–4 answer: A magnet has two ends called a north pole and a south pole. Like poles push apart (repel) and unlike poles pull together (attract). Iron, steel, cobalt and nickel are attracted to magnets. The magnetic field lines show where the force acts and they go from N to S.
Grades 6–7 answer: A permanent magnet has a north-seeking pole and south-seeking pole. The region around the magnet is called a magnetic field, represented by magnetic field lines that point from N to S outside the magnet and never cross. Where lines are closer, the field is stronger. Like poles repel and unlike poles attract. Only certain ferromagnetic materials (iron, steel, cobalt, nickel) respond to magnetic fields.
Grades 8–9 answer: A permanent magnet produces its own magnetic field even with no external influence. Magnetic field lines form continuous closed loops from N to S outside and S to N inside the magnet, and their density represents the magnitude of the magnetic flux density B. The Earth's magnetic field resembles that of a giant bar magnet with its magnetic south pole near geographic north; a compass needle, itself a small permanent magnet, aligns with whichever local field dominates. At GCSE, ferromagnetism is restricted to iron, steel, cobalt and nickel; all other common metals (copper, aluminium, gold) are non-magnetic because their atomic magnetic moments do not align coherently.
AQA alignment: This content is aligned with AQA GCSE Combined Science: Trilogy (8464) specification section 6.7 Magnetism and electromagnetism — specifically 6.7.1 Permanent and induced magnetism, magnetic forces and magnetic fields. Assessed on Physics Paper 2.