Heating appliances and safety

Now a whole shelf of appliances makes sense. Room heaters, electric stoves, kettles, irons, immersion rods for heating a bucket of water, and hair dryers all work on the heating effect of electric current.

Each has a rod or coil of wire inside called a heating element, usually made of a high-resistance wire such as nichrome. In some you can see it glowing red-hot. The wiring in your walls is copper, chosen for the opposite reason: it resists little, so it stays cool.

But the heating effect isn't always wanted:

• power lines lose energy, because the wires warm up as the current travels long distances;
• appliances that overheat can damage plugs and sockets: their plastic parts can melt, and that can even start a fire.

So household circuits have safety devices that cut the current before things get dangerous.

And to stop switchboards overheating, always use wires, plugs and sockets rated for the current they will carry. A small plug on a big heater is asking for trouble.

Industry uses the heating effect too. In steel-making, an electric furnace (an enclosed space built to make great heat) uses current to melt scrap steel and turn it into usable new steel.