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Loose electrons, and a price that works

Why Are Wires Made of Copper?

Silver conducts electricity slightly better than copper. Almost every wire is copper anyway.

An ordinary lengthof wire Electrons driftingloose between theatoms
A metal is atoms sitting in a sea of loose electrons.

  1. Step 1 of 5

    A metal's outer electrons are not held tight.

    A fixed grid ofcopper atomsEach lets its outerelectron goA sea of them, freeto moveMoving electrons areelectricity
    The atoms stay put. The electrons do not.

    In copper, each atom lets its outermost electron wander. The result is a fixed grid of atoms sitting in a sea of electrons that are free to move — and moving electrons are electricity.

  2. Step 2 of 5

    A current is a slow drift.

    The push Travels almostinstantlyThe electrons Drift slower than asnail

    Switch a light on and it comes on immediately, but the electrons themselves crawl along slower than a snail, less than a metre an hour. The push travels almost instantly; the electrons barely move at all.

  3. Step 3 of 5

    Silver is better, and nobody uses it.

    Silververy slightlybetterCopperalmost as good,and cheapAluminiumworse, butlighter andcheaper still

    Silver conducts slightly better than copper. It is also far too expensive to run through the walls of every house, so copper wins on price by an enormous margin.

  4. Step 4 of 5

    It bends without snapping.

    What a wire has tosurviveCopper: drawn thin, bent, squashedMost good conductors snap
    Conducting well is only half the job. The other half is surviving the walls.

    A wire has to be pulled through walls, bent round corners and squashed into plugs. Copper can be drawn into thin wire and bent repeatedly without breaking, which most good conductors cannot.

  5. Step 5 of 5

    Resistance turns electricity into heat.

    Electrons bumpinto atoms Every bump makesa little heat

    The drifting electrons keep bumping into the atoms, and every bump makes heat. In a wire that is waste; in a kettle element or a toaster it is precisely the point.

    Overhead power lines are aluminium, not copper. Over hundreds of kilometres, being light matters more than conducting slightly better.

The short version

Copper carries electricity because its outer electrons drift free — and it wins over silver on price and bendiness.

Try it yourself

Feel a phone charger cable after a long charge. It is slightly warm, and that warmth is electrons bumping into atoms.

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