Plot and draw magnetic fields using a compass, showing changes in strength and direction, and relate compass behaviour to evidence that Earth’s core is magnetic.
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GCSE Physics Revision
Learn it. Recall it. Revise it.
GCSE Physics revision
Magnetic fields
Permanent and induced magnetism, magnetic forces and fields
Your specification
AQA student objectives
Learning pathway
All · Most · Some
Apply the scientific explanation of magnetic fields to a relevant example.
Analyse a new situation involving magnetic fields and explain the scientific reasoning.
Revision summary
Key knowledge
Read on screen, then print for Cornell-style active revision.
What Is a Magnet?
- A magnet is any material or object that produces a magnetic field, ranging from simple bar magnets and horseshoe magnets to the Earth itself.
- All magnets share two key features: a north pole and a south pole, and they are surrounded by a magnetic field.
Representing Magnetic Fields with Field Lines
- Magnetic field lines are arrows drawn around a magnet to represent the direction and shape of the magnetic field.
- Field lines always travel from the north pole to the south pole on the outside of the magnet.
- To draw field lines correctly, start with straight lines directly into and out of the poles, then add curved lines, and finally lines that loop all the way around from north to south.
- Always check that every arrow points outward from the north pole and inward towards the south pole.
Field Line Density and Magnetic Field Strength
- The density of field lines — how closely packed together they are — indicates the relative strength of the magnetic field in that region.
- Where field lines are closer together, such as near the poles, the magnetic field is stronger than in regions where the lines are more spread out.
Using a Compass to Map Field Lines
- A compass needle is itself a tiny bar magnet, so it aligns with the magnetic field lines of any nearby magnet.
- The compass needle always points towards the south pole of a magnet, allowing you to identify which pole is which.
- By placing a compass in many different positions around a magnet and recording the needle's direction each time, you can map out the full pattern of field lines.
- Joining up the recorded arrows produces the same field line diagram as drawn theoretically.
Identifying Poles Using a Compass
- If a compass needle points towards a magnet, that end of the magnet is the south pole.
- If a compass needle points away from a magnet, that end of the magnet is the north pole.
Repulsion Between Like Poles
- When two north poles (or two south poles) are brought close together, the magnets repel each other.
- The field lines between two like poles curve away from each other, and it is this interaction of the magnetic fields that creates the repulsive force.
Attraction Between Opposite Poles
- When a north pole and a south pole are brought close together, the magnets attract each other.
- The field lines travel continuously from the north pole of one magnet to the south pole of the other, producing an attractive force between them.