Why are electric wires covered up?

   Electricity is very useful as long as we don't get in its way. But it can make trouble for us if we do. Luckily we have a way of avoiding it. We can wrap electrical wires in coats of rubber or plastic. These coats are called insulation. Electricity can't travel through a coat of insulation, and so it runs along safely inside the wire.
If a current of electricity runs through you, it gives you a shock and strong shocks are dangerous. They can kill you. So it is safest not to meddle with electric wires or machines.