What a magnet attracts

Figure 13.2 shows some objects that are not attracted to a magnet, and some that are.

Figure to be added

Figure 13.2 — (a) a magnet held over a plastic pen cap, an eraser, rubber bands, a match stick, pieces of paper and a plastic button: none move; (b) the same magnet over drawing pins, sewing needles, paper clips, an iron nut and a safety pin: all are pulled up.

Attracted

Objects made of metals such as iron, steel and nickel.

Drawing pins, needles, paper clips, nails, safety pins

Not attracted

Objects made of materials such as plastic, wood, paper and rubber.

Pen caps, erasers, rubber bands, matches, paper, plastic buttons

Why only some metals

It is tempting to say that magnets attract metals, but that is not quite right. Iron, steel, nickel and cobalt are attracted strongly; these are called magnetic materials. Most other metals — copper, aluminium, brass, gold, silver — are not noticeably attracted at all. A coin made of copper-nickel alloy may or may not stick, depending on how much nickel it has. This matters in the rest of the chapter: the core of an electromagnet or transformer is made of iron because iron is a magnetic material, while the wires wound on it are copper, which is not, and conducts electricity well.

Not every metal is magnetic

An aluminium can or a brass key is a metal but is not attracted to a magnet. Only iron, steel, nickel and cobalt, and some of their alloys, are.

Magnetic materials

Iron, steel and nickel are attracted to magnets; plastic, wood, paper and rubber are not.