Describe magnetic poles (north and south), explain attraction and repulsion between poles, describe magnetic field lines plotted using a compass, and explain the Earth's magnetic field and its practical uses
You already know that magnets have a north pole and a south pole, and that like poles push apart while unlike poles pull together. That pushing and pulling happens because every magnet is surrounded by an invisible area called a magnetic field.
Field lines show the shape of this invisible area. Each line leaves the north pole, loops around the magnet, and goes back in at the south pole. You can see this pattern for real by moving a small compass around a bar magnet and marking which way the needle points at each spot.
Mia moves a compass step by step around a bar magnet. Close to the poles, the needle swings quickly and the lines she draws are packed tightly together. Further away, the needle turns more slowly and her lines spread out. This tells her the field is strongest near the poles.
The Earth behaves like a giant bar magnet buried inside it. That is why a compass needle always swings around and settles pointing roughly north: it is lining up with the Earth's own magnetic field, just like it lines up near a bar magnet.
A compass works because its needle is a tiny magnet that can swing freely. It lines up with any magnetic field it sits in, whether that field comes from a bar magnet or from the Earth itself. One more rule helps you read a field map: field lines never cross each other. At every spot the field points in just one direction, so two lines can never meet.
A magnet's field lines run from its north pole to its south pole, and Earth's own magnetic field is what makes every compass point north.
Mia has played with bar magnets before. She knows the letters N and S, and that same poles push apart while different poles pull together. Today she wants to see the push itself, the invisible part around one bar magnet.
What is the invisible area around a magnet called?
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