Permanent and Induced Magnetism and Magnetic Fields — AQA GCSE Physics
Magnets produce magnetic fields, and magnetic materials can be magnetised by being placed in a field.
Permanent and induced magnets
- A permanent magnet produces its own magnetic field all the time, with a north and a south pole.
- An induced magnet becomes magnetic when placed in a magnetic field, and loses most of its magnetism when removed.
Magnetic materials are iron, steel, cobalt and nickel.
Forces between poles
- Like poles repel; unlike poles attract.
- Induced magnetism always causes a force of attraction. These are non-contact forces.
Magnetic fields
A magnetic field is the region around a magnet where a force acts on another magnet or magnetic material.
- Field lines run from the north pole to the south pole outside the magnet.
- The field is strongest where the field lines are closest together — at the poles.
- The direction of the field at a point is the direction a compass (north pole) would point.
The Earth's magnetic field
A compass needle (a small magnet) points roughly north because the Earth has its own magnetic field. This is evidence that the Earth's core is magnetic.
Exam tips
- Distinguish permanent (always magnetic) and induced (temporary, always attractive) magnets.
- Like poles repel, unlike attract.
- Field lines go N → S; strongest at the poles.
- A compass shows the Earth has its own magnetic field.