Magnets & magnetic force
The idea
A magnet pulls on certain metals without touching them — hold one near a steel paper clip and the clip jumps across the gap. That invisible pull is called magnetic force. Magnets have two ends, called poles. Two magnets can pull toward each other or push apart, depending on which ends face each other. The push and pull work right through air, and even through thin things like paper or a tabletop.
The most useful fact to remember: magnets do not attract everything, and they do not even attract all metals. They grab things made of iron or steel, while plastic, wood, paper, and most other metals ignore them completely. That is the big mix-up to avoid — shiny does not mean magnetic. A ball of aluminum foil and many coins are metal, yet a magnet will not pick them up. The honest way to find out is always the same: test it.
Worked example
You test a magnet on 6 things: a steel paper clip, a crayon, a ball of aluminum foil, a steel spoon, a wooden block, and a rubber band. Then you put a sheet of paper between the magnet and the paper clip. What sticks?
- Predict first: many people guess that all the metal things — the foil ball, the clip, and the spoon — will stick, since they are all shiny metal.
- Test each one: the paper clip and the steel spoon snap onto the magnet, while the crayon, the wooden block, and the rubber band do nothing at all.
- Now the surprise: the aluminum foil ball does not stick either, even though it is metal. So the rule is not that metal sticks — the rule is that iron and steel stick.
- Sort the results: 2 out of the 6 things stuck, and both of them are made of steel, which contains iron.
- Run the last test: hold the magnet on one side of the paper sheet and the clip on the other — the clip still clings through the paper. Magnetic force reaches through thin materials.
Answer. Only the 2 steel things — the paper clip and the spoon — stick to the magnet, and the pull even works through a sheet of paper.
Check your understanding
- What test would settle an argument about whether a shiny toy is steel or aluminum, and what result would you expect for each?
- Why is it a mistake to say that magnets attract metal, and what is the more careful rule?
- What do you feel when you bring two magnets close together in different ways, and what does that tell you about their two ends?
- Where do magnets help out around your home, and what is each one pulling on or holding shut?