Electric current flows in a loop, so a broken wire stops the whole circuit.

The longer version

An electric current is a drift of charge that needs an unbroken path. Electrons move through the wire, through the device doing the work, and back to the source, so the flow forms a closed ring. Cutting the ring anywhere leaves charge with nowhere to go, and everything on that path stops.

A switch works by deliberately opening and closing such a gap. Homes are wired so that each fitting sits on its own branch, which is why one broken lamp does not darken the whole building. Conductors inside the cable provide the path, while insulation keeps charge from escaping sideways.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.