Electric circuits — Science, 11–13 years
A circuit gives electric charge a complete route through components, so devices can work. You will see why a break, a switch or a different arrangement changes what happens.
The idea
Electricity in a simple circuit is not a one-way stream that disappears inside a bulb. Charge moves around a complete loop, while the battery pushes it and the components change what the circuit can do. Open the loop, and the movement stops.
Why circuits matter
People needed a reliable way to make a lamp, bell or motor work only when wanted. The circuit idea solves this by controlling one complete route with a switch. It also helps explain failures: a loose wire or flat battery can stop the whole loop.
A torch circuit
A battery has two terminals, a bulb has two contacts, and a switch is placed between them. Connect the positive terminal to one bulb contact, the other contact to the switch, and the switch back to the negative terminal. Close the switch: the loop is complete and the bulb lights.
The common mistake
A common mistake is connecting both wires to the glass of a bulb, or touching only one battery terminal, and expecting light. That seems reasonable because the bulb and battery are present. Electricity needs metal contacts and one unbroken route from one terminal around to the other.
Where it appears
Every torch, doorbell and bicycle light uses a circuit that can be opened and closed. In a home, switches and safety devices control routes carrying much more electrical energy than a small classroom circuit. Never test household sockets: use a low-voltage kit with an adult.
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