Key points
Magnetism is an invisible forceA force is a push or a pull that acts on an object due to the interaction with another object. that affects materials such as iron, steel, nickel and cobalt.
A compassA device with a magnetised needle. The needle turns to line up with a magnetic field. can be used to detect both the Earth’s magnetic fieldThe region around a magnet where a force will be experienced. and the field around other magnets.
This guide will show you how to make your own magnetic detector, a compass.
Watch this video to learn how to make a magnetic compass
Give it a try yourself
Image caption, WHAT YOU NEED: A bowl of water, cork, sewing needle and a compass.
Image caption, Rub the needle 50 times along the magnetic strip on a fridge door. Make sure you do this in one direction only.
Image caption, Place the magnetised needle onto the piece of cork.
Image caption, Gently place the needle and cork into the bowl of water.
Image caption, The needle will turn and then come to a complete stop. It will be facing magnetic north. You can check this by placing the compass next to the bowl.
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Why does the needle move?
The needle is being affected by the Earth’s magnetic field. One end points towards magnetic north and the other end points south. You can use a compass to check which direction each end is facing.
The Sun is in the South at about midday, so you can also check your compass is working if one end points in that direction. The other end of the needle will be pointing north, away from the Sun.
Where are compasses used?
When it is dark or foggy, ships need to know they are sailing in the right direction. A ship’s navigator uses a compass to check that they are still on course. Explorers also use a compass to help them find their way and avoid getting lost.
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