Skip to content

A compass

Electricity and magnetism · level 1, lesson 3 of 6

A question to start

A compass needle swings round and stops, pointing the same way every time. Turn the compass, and the needle swings back. What is pulling it?

The idea

A compass needle is a tiny magnet that can spin freely. It lines up with the Earth, because the whole Earth acts like a giant magnet.

  • The needle's north end points north.
  • Once you know where north is, you can find south, east and west.

About a thousand years ago, sailors in China were already using compasses to find their way at sea, in fog and at night. Sailors everywhere soon did the same.

Bring a magnet close to a compass and the needle turns to point at the magnet instead. So keep magnets away when you use one.

NSEW

Worked examples

1. Finding north. Hold a compass flat and still. Turn your body until the needle's north end points straight ahead. You are facing north.

2. Behind you. If you face north, south is behind you, east is on your right and west on your left.

3. A fooled compass. Move a fridge magnet round a compass. The needle follows the magnet, not the Earth.

Try it

  1. What is a compass needle?
  2. Why does a compass needle point north?
  3. You face north. Which way is on your left?
  4. Why should you keep magnets away from a compass?
Answers
  1. A tiny magnet that can spin.
  2. The Earth acts like a giant magnet, and the needle lines up with it.
  3. West.
  4. The needle would point at the magnet instead of north.

Common mistake

"A compass points to the North Pole because it is cold there." It points along the Earth's magnetism, nothing to do with ice or cold.

Where it leads