Ben Fenton, a pupil at Balclutha Primary School, asks :-
Why does electricity go through metals?
Simon Brown, a physicist at the University of Canterbury, responded.
The first thing we have to do is to understand what is meant when we say that electricity is going through a metal. We really mean that electric charge is flowing ie. that electrons are able to move around in the metal. We are used to thinking of electrons as orbiting the nucleus of an atom (a bit like the earth moving around the sun). This picture is more or less correct for single atoms - the electrons are 'stuck to the atom' and can't move away. However, any solid material is made up of a thousand billion billion atoms per cubic centimetre and the picture is then rather different. In some types of solid the electrons that are furthest from the nucleus find that they can easily jump to the next atom and then to the next and so on and so on. We call these solids metals. So many electrons are continuously jumping around that we can picture a 'sea of electrons' inside the metal. It is the movement of this sea of electrons that allows the metal to conduct electricity.
In some solids (like glass) the electrons remain stuck to the atoms and can't move easily. We call these materials insulators. In some ways insulators are just as important as metals, without the insulating plates that you can see between copper electricity cables and the pylons that carry them, the electricity from a power station would leak away before it could get to your house.