ClosedCircuit

A closed circuit is an electrical circuit in which a complete conductive path exists, allowing current to flow from a power source through conductors and components back to the source. The essential elements are a power source, conductive wiring, and a load that uses electrical energy. A switch or other device may be used to open or close the circuit.

If any break occurs in the path—such as an open switch, a damaged wire, or a blown fuse—the circuit becomes open and current cannot flow. In contrast, a closed circuit permits continuous current flow, though real circuits always encounter some resistance, inductance, and capacitance that shape the behavior of the current.

In analysis, closed circuits can be described using Ohm’s law and impedance concepts. Direct current (DC) circuits have a constant flow, while alternating current (AC) circuits involve changing directions. Components in a closed circuit may be arranged in series, where the same current passes through all components, or in parallel, where components share the same voltage but may carry different currents.

A closed circuit can still experience faults, such as a short circuit, where an unintended low-resistance path causes unusually high current. This can heat conductors and trip protective devices. Practical circuits are designed with safety margins, insulation, proper gauge wires, and protective devices such as fuses or circuit breakers to prevent damage.

Closed circuits are foundational to most electrical systems, from simple devices to complex power networks, and are distinguished from open circuits, where the path is incomplete and current cannot flow.