A circuit carries electrical energy from its source to a device.
Over-head cables carried by pylons are components in large circuits from the powerstation to our homes, schools and factories.
Our homes have mains circuits, which carry electricity to every room.
Electrical appliances have circuits inside them.
To allow the electricity to flow, the circuit must be a complete loop, with no gaps. Circuits are made using conducting materials (metal wires) which allow the electricity to flow, and insulating materials (plastics) which stop the flow of electricity.