Look at a lamp cord: a soft plastic coat outside, shiny copper wire inside. Why both?
Key idea
Conductors let electricity flow through them easily: metals like copper, aluminum, iron and silver. Insulators stop it: plastic, rubber, wood, glass, cloth and paper.
The copper inside a wire carries the current. The plastic outside keeps the current in the wire and keeps people safe.
Worked example: Test the coin
A steel coin is put across the gap in a circuit. Does the bulb light?
- Steel is a metal.
- Metals are conductors.
Answer: Yes, it lights.
Common mistake
Thinking anything shiny conducts. Shiny plastic or a shiny painted pencil does not. Metal does, even when it is dull or rusty-looking.
Water from a tap carries electricity well enough to be dangerous, which is why we keep electrical things away from sinks and baths.
Try it at home
- Collect a spoon, a key, a pencil, a plastic cup, a rubber band, a piece of foil and a paper clip.
- Guess which are conductors. Then build each one into the gap in the Circuit Builder, or check against the table above.