Components of an Electric Circuit

Core concept

For current to flow and a bulb to light up, the circuit must be complete (closed) — if there is any break, such as an open switch or a disconnected wire, the circuit becomes open and no current flows, so the bulb stays off. Conductors, like copper wires, allow current to pass through easily, while insulators, like rubber or plastic, block current flow and are used to safely coat wires and prevent electric shocks.