Magnetism · revision map · IGCSE 0625, Topic 4.1
TOPIC 4.1 · MAGNETISM
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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MAGNETISM4.1
Magnetic Poles & Forces
Every magnet has a north pole and a south pole.
- Like poles repel; unlike poles attract.
- The magnetic force acts at a distance, without touching.
- Magnetic materials: iron, steel, cobalt, nickel.
Induced Magnetism & Materials
A magnetic material placed near a magnet becomes a magnet itself: this is induced magnetism.
Soft (iron)
magnetises and loses it easily; ideal for electromagnet cores.
magnetises and loses it easily; ideal for electromagnet cores.
Hard (steel)
hard to magnetise but keeps it; ideal for permanent magnets.
hard to magnetise but keeps it; ideal for permanent magnets.
Magnetic Fields
A magnetic field is the region where a magnet exerts a force on magnetic materials and other magnets.
- Field lines run from north to south outside the magnet, and never cross.
- The closer the lines, the stronger the field.
- A plotting compass shows the field direction.
Using Magnets
Magnets and their fields are used widely in everyday life.
- A compass needle lines up with Earth's field and points north.
- Magnetic catches hold doors and fridges shut.
- Magnets separate steel from other scrap.
- A current can make a magnet too: the electromagnet leads into Topic 4.5.
Plotting a Field with a Compass
A small plotting compass maps the shape of a magnetic field.
- The needle points along the field line at each spot.
- Mark the ends, move the compass, and join the dots.
- Arrows on the lines run from N to S outside.
The Earth as a Magnet
The Earth behaves like a giant bar magnet, which is why a compass works.
- A freely suspended magnet settles roughly north–south.
- The end that points north is the magnet's north-seeking pole.
- This is how a compass is used for navigation.