Conductors and insulators · Grade 3
A conductor lets electricity flow through it easily; an insulator does not. Metals are good conductors, which is why wires are made of copper. Plastic, rubber, wood and glass are insulators, which is why they are used to cover wires and make plugs and switches safe to touch.
Key facts
- Metals (copper, iron, steel, aluminium, gold, silver) are good electrical conductors.
- Graphite (pencil “lead”) is the only common non-metal that conducts well.
- Plastic, rubber, wood, glass, wool, paper and air are insulators.
- Test a material by putting it in the gap of a circuit: if the bulb lights, it conducts.
- Water with salts in it (tap water, sweat) conducts – never touch electrical things with wet hands.
- Long, thin wires resist current more than short, thick ones.