CoachA magnet is a special piece of stone or metal that pulls certain things toward itself without touching them. We say the magnet attracts them. The things it attracts stick to it; the rest do not care about it at all.
Examples
Example 6.2 (Try it: the grabbing test)
Walk around your home with a magnet and try it on: a paperclip, a nail, the refrigerator door, a wooden spoon, a plastic brick, a sheet of paper, a glass, a cork. The magnet grabs the paperclip, the nail and the refrigerator door — and ignores every one of the others. Only some things obey magnets.
Example 6.3 (The magnet’s favorite metal)
Look at what got grabbed: paperclip, nail, refrigerator door. They are all made of iron (or of steel, which is mostly iron). Wood, plastic, paper, glass, stone: never. And here is the fine surprise: even some metals are ignored — try a coin or a sheet of kitchen foil. A magnet is not a metal-lover; it is an iron-lover.
Example 6.4 (Try it: grabbing through things)
Put a paperclip on the table and hold your magnet under the tabletop, just below the clip. Move the magnet: the clip slides around the table as if by magic — the pull goes right through the wood. It also works through paper, through cardboard, through a glass of water: drop a clip in the glass and walk it up the side with the magnet, keeping your fingers dry.