Why do magnets attract or repel each other?
Short answer: every magnet has a north and a south pole. Opposite poles (north facing south) attract each other, like poles (north-north or south-south) repel. When attracting, the field lines of one magnet continue into the other; when repelling, the fields push against each other. Both forces get stronger quickly as the magnets come closer together.
Attract or repel: overview
| Combination | Result |
|---|---|
| North – south | attract |
| North – north | repel |
| South – south | repel |
| Magnet – steel (any pole) | always attract |
Steel is attracted by either pole, because it temporarily forms an opposite pole itself. See how does a magnet work? Repulsion is therefore the only real proof that something is a magnet.
Why does the force get stronger so quickly?
The field of a magnet drops off quickly with distance. As a result, the force between two magnets at short distance is many times greater than at a few centimetres. That is why magnets feel almost nothing until a few centimetres apart and then snap together with force over the last bit. With large neodymium magnets, this can pinch fingers and make the magnets shatter.
How do you find the north and south pole?
- With a compass: the north tip of the compass needle points to the south pole of the magnet.
- With a marked magnet: a known north pole repels the north pole of another magnet.
- With a smartphone: a magnetometer app shows the field as positive or negative.
- Marked by us: we supply some countersunk magnets as a north pole or south pole version, so that two magnets are sure to attract each other.
Tip: mark the poles with a marker before gluing magnets in. A magnet glued in the wrong way round repels instead of attracts.
Repulsion in practice
- Magnetic levitation experiments: a magnet will not float stably above another magnet on its own (Earnshaw's theorem). There is always a guide, rotation or control system needed.
- Maglev trains and magnetic bearings: use controlled electromagnets or superconductors.
- Electric motors: turn through alternating attraction and repulsion between permanent magnets and coils.
- Damping and springs: repelling magnets act as a contactless spring.
Frequently asked questions
Is repulsion as strong as attraction?
At the same distance, roughly yes. When repelling at very short distance, strong magnets can partially demagnetise each other, especially when warm.
Can you make a separate north or south pole?
No. If you break a magnet in half, you get two magnets, each again with a north and a south pole. A separate magnetic pole (monopole) has never been found.
Why does a magnet flip over when I move it towards another magnet?
Like poles push each other away. If the magnet can rotate, it turns until the opposite poles face each other and it clicks into place.
Read also
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