Step 1 of 6 Magnets and magnetic fields
Two ends that matter
Every magnet has two ends, called poles: a north pole and a south pole. Bring two magnets together and their poles decide what happens: unlike poles attract, like poles repel. Here the north ends are painted red and the south ends blue, as in a classroom; real magnets aren't coloured.
Make the two magnets push each other away.
If you cut a bar magnet in half, what do you get?
Step 2 of 6 Magnets and magnetic fields
The invisible field
A magnet's push and pull reaches out into the space around it. That space is its magnetic field. You can't see it, but tiny iron filings can: each one turns to line up with the field, and together they draw its shape.
Sprinkle the filings and look where they crowd together. Where is the field strongest?
Put two magnets end to end. Try north facing south, then north facing north, and watch the filings.
Step 3 of 6 Magnets and magnetic fields
Follow the compass
A compass needle is a tiny magnet on a pivot. It turns until it lines up with the field it sits in. So a compass shows the field's direction: its north end points along the field, which runs out of a magnet's north pole and round into its south pole.
Move the compass to just beyond the magnet's red north pole. Which way does the compass's north end point?
Move the compass far away from the magnet. Where does it point now?
Step 4 of 6 Magnets and magnetic fields
What sticks?
Iron and steel (which is mostly iron), and also nickel and cobalt, are strongly attracted to magnets. Most other materials, including many metals, are not noticeably attracted. A magnet can even turn a piece of iron into a temporary magnet.
Strong magnets can pinch fingers and can harm phones, bank cards and pacemakers. Keep them away from these, and from small children.
Try the magnet on each object. Find every object it picks up.
With a paperclip hanging from the magnet, touch a second paperclip to the first. Does it hold on?
Step 5 of 6 Magnets and magnetic fields
Earth is a magnet
Earth behaves like a giant bar magnet, made by molten iron flowing deep inside it. Its field reaches all over the planet, so a compass anywhere lines up with it and points roughly north. That's how people have found their way for a thousand years.
A compass's north end is attracted towards the Arctic. So is Earth's magnetic pole in the Arctic a north pole or a south pole?
Does a compass point exactly at the North Pole?
Step 6 of 6 Magnets and magnetic fields
Electricity makes magnetism
In 1820 Hans Christian Ørsted noticed a compass needle swing whenever current flowed in a nearby wire: an electric current makes a magnetic field. Wind the wire into a coil round an iron core and the field becomes strong. That's an electromagnet, a magnet you can switch on and off.
Use the electromagnet to lift the paperclips, then drop them.
Scrapyards lift cars with huge electromagnets rather than ordinary magnets. Why?
Quiz Magnets and magnetic fields
Check what you know
Six questions, 5 points each. One answer per question.
Done Magnets and magnetic fields
Lesson complete
Now you know why magnets snap together or push apart, what a field is, why a compass points north, and how a current makes a magnet you can switch on and off.
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