A simple circuit — Physical education, 7–10 years
Electric current needs a complete path. A battery, wires and a lamp can work together when the path is closed.
Electricity needs a complete loop
In a simple circuit, electricity travels around a complete loop from one battery terminal, through the wires and device, to the other terminal. If there is a gap, the path is broken and the lamp stays off. A switch works by opening or closing that gap.
Why does the loop matter?
Early experimenters found that a battery did not light a lamp just because wires touched it. They needed a continuous path through the lamp and back to the battery. This idea solves the problem of predicting why a device works, fails or can be turned off safely.
Lighting one small lamp
Use one battery, two wires and a small lamp. Connect one wire from the battery’s positive terminal to the lamp, then connect the second wire from the lamp to the battery’s negative terminal. The loop is complete, so current flows and the lamp lights.
Two wires touching is not enough
It is reasonable to think electricity jumps from a battery into a lamp whenever a wire touches each one. But the current needs a complete route back to the battery. One wire may touch both parts and still leave no loop, so the lamp stays off.
Torches and household devices
A torch has a battery, wires, a lamp or LED and a switch arranged as a circuit. Pressing its button closes the path; releasing it opens the path. Homes use much larger circuits to power lights and appliances, with safety parts that stop dangerous currents.
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