Electric circuits:
An electric circuit is a path along which electricity can flow. To make up a circuit you need a battery, a bulb and two wires. The wires and used to join the battery to the bulb. The batteries job is to push an electric current trough the wires and the bulb. The bulb lights up as the current flows I through it.
Meters and switches:
If you want to measure the size of the current, you have to put a meter into the circuit. Current is measure in amperes (A) or amps for short.
The meter for measuring current is called an ammeter.
If you want to turn the bulb on and off easily you should use a switch. A switch works by opening and closing a gap in the circuit. When the switch is turned off, a gap opens up. This stops the flow of current all round the circuit.
When the switch is turned on, the gap is closed this makes a complete circuit and the current can flow.