Electric Circuit

An electric circuit is a system of conducting elements designed through which electric current flows. (The word “circuit,” although now restricted mostly to electrical use, once signified any path that closed on itself, such as a racetrack.) Circuits may be artificial or natural. Artificial circuits consist of sources of electric energy such as generators and batteries; elements that transform, dissipate, or store this energy, such as resistors, capacitors, and inductors; and connecting wires. Circuits often include a fuse or circuit breaker to stop the flow of current from becoming excessive (a fire or device-damage hazard).

Devices may be connected in a circuit in one of two ways, series or parallel. A series circuit forms a single pathway for the flow of current, while a parallel circuit offers separate paths or branches for the flow of current.

The first electric circuit was invented by Alessandro Volta (1745–1847) in 1800. He discovered he could produce a steady flow of electricity using bowls of salt solution connected by metal strips. Later, he used alternating discs of copper, zinc, and cardboard that had been soaked in a salt solution to create his voltaic pile (an early battery). By attaching a wire running from the top to the bottom, he caused an electric current to flow through his circuit. The first practical use of the circuit was in electrolysis, which led to the discovery of several new chemical elements. Georg Ohm (1787–1854) discovered some conductors had more resistance than others, which affects their efficiency in a circuit. His famous law states that the voltage across a conductor divided by the current equals the resistance, measured in ohms. Resistance causes heat to be dissipated in an electrical circuit, which is sometimes wanted and sometimes not.

See also Electrical conductivity; Electrical power supply; Electrical resistance; Electronics; Integrated circuit.