Simple circuits

The diagram shows the workings of a simple torch. When the button B is pressed, electricity flows around the circuit and the torch bulb glows. When the button is released, electricity stops flowing around the circuit and the bulb no longer glows.
Like water flowing through pipes, electricity needs something to travel through. The ‘pipes’ for electricity are metal wires. The wires, batteries and bulbs form circuits around which currents flow.
Cells and batteries:
A cell is a kind of pump which makes electricity move. This movement is called an electric current. If a larger current is need several cells can be connected together to form a battery.
Both circuits shown in figures 2 and 3 are complete circuits. Electricity can flow all the way around them. But if a gap is created in the circuit, electricity will not flow and the bulb will not glow. We describe a circuit like this as being incomplete. The position of the gap in the circuit is unimportant. Current will only flow if the circuit is complete.
Switches:
A switch turns a circuit on and off. It behaves like a draw bridge which can make the circuit complete when closed, or incomplete when open.
Circuit diagrams:
Drawing diagrams such as those shown opposite is not easy. To simplify things scientists and electricians use circuit diagrams. These simple diagrams use symbols to represent the various bits and pieces (more properly called components) of the circuit. A list of some of the most common components is shown above.