Hayden McKenzie, of Ardgowan School, asks :-
Where does electricity go when you have finished with it?
John Bahr, a physicist at Otago University, responded.
Imagine a rotating garden sprinkler attached to a hose which is in turn screwed onto a tap. When you turn on the tap, water flows from the tap, through the hose, and causes the sprinkler head to rotate. It is the energy carried by the water that causes the sprinkler to rotate, and the pressure of the water from the tap which drives the water through the hose.
Electricity is a form of energy which uses electric charge flowing through conductors like copper wire. Imagine an electric fan which is connected by a mains cable (the copper wires) to a wall socket which has a switch. When you turn on the switch, the `electrical pressure' drives the charges along the cable and the charges carry their energy to the fan causing it to rotate.
Now in the case of the hose and sprinkler, when you turn off the tap the sprinkler stops rotating even though the hose is still full of water, because there is no longer any driving pressure. In a similar way, when you turn off the electrical switch the fan stops rotating even though the wires still have all the electrical charge inside them, because there is no longer any `electrical pressure'. So the electricity doesn't go anywhere - it has just stopped working for a while.