Magnets and magnetic fields
What you need for the magnetic properties in Chapter 1
1. Magnets and magnetic fields: from zero
2. Metal, but not pulled
A fridge magnet sticks to a steel fridge door. Hold it near an aluminum soda can, and nothing happens.
Pick the right answer
Why doesn't the magnet pull the can?
- A. The can is too light for the magnet to notice
- B. A magnet strongly attracts only some materials, like iron, and aluminum is not one of them
- C. Magnets attract all metals, so the can must have a plastic coating
Explanation
A magnet strongly attracts only some materials, such as iron, cobalt and nickel. Aluminum is a metal, but a magnet doesn't noticeably pull it, so the can is not pulled.
3. The magnetic field
magnetic field
The region around a magnet where its magnetic force acts.
The field is invisible. Put iron filings near the magnet and they line up along these lines.
True or false?
A magnet attracts all metals.
Explanation
A magnet strongly attracts iron, cobalt and nickel (and steel, which is mostly iron). Copper, aluminum, gold and silver are metals too, but a magnet doesn't noticeably pull them, so not all metals are attracted.
4. Poles: pull or push
Every magnet has two poles: north (N) and south (S).
So a magnetic field can pull something in, or push it away. You'll need both ideas in Chapter 1.
5. Pulled or not?
Sort into groups
Bring an ordinary magnet near each object. Sort them.
iron nailsteel paper clipa piece of cobaltcopper wirealuminum foilgold ring
Pick the right answer
Two bar magnets lie end to end. The S pole of one faces the S pole of the other. What happens?
- A. They attract
- B. They repel
- C. Nothing, unless they touch
Explanation
S facing S means like poles, and like poles repel, so the two magnets push each other apart. Magnets act on each other across the gap without touching.
6. Summary
| Pulled strongly by a magnet | Metals not noticeably pulled |
|---|---|
| iron (and steel) | copper |
| cobalt | aluminum |
| nickel | gold, silver |
- A magnet has a magnetic field around it: the region where its magnetic force acts.
- Like poles repel; unlike poles attract.
- A magnet strongly attracts iron, cobalt and nickel, not all metals.
Can you explain why a magnet pulls a steel door but not an aluminum can?