A circuit must be complete — Physical education, 11–13 years
Electric current can flow around a complete conducting path. A battery provides a push, and components such as lamps transfer electrical energy into light and heat.
One unbroken path
In a simple circuit, charge can move around a complete loop from one battery terminal, through components and back to the other terminal. A lamp lights because current passes through its filament or electronics. A gap anywhere in the loop stops the current.
Why draw circuits?
Wires and components can become a confusing tangle, especially when a circuit has several lamps or switches. Circuit diagrams replace each part with a symbol and show the connections clearly. This makes it possible to predict whether current has a complete route before building it.
Finding the break
A battery, two wires, a switch and a lamp are connected, but the lamp stays dark. Check the path from one battery terminal: wire, switch, wire, lamp, then wire back to the other terminal. The switch is open, leaving a gap. Close it and the loop is complete, so the lamp lights.
A battery is not enough
It is reasonable to think a battery makes a lamp light simply because it stores electrical energy. But the energy can reach the lamp only through a complete conducting path. One loose wire, an open switch or a plastic gap prevents the loop from working.
Circuits around us
Torches, doorbells, toys and phone chargers all use circuits. A switch opens or closes a path, while sensors can change a circuit when light, heat or movement changes. Bigger systems contain many linked circuits, but each still needs controlled paths for current.
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