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electric circuit

electric circuit, unbroken path along which an electric current exists or is intended or able to flow. A simple circuit might consist of an electric cell (the power source), two conducting wires (one end of each being attached to each terminal of the cell), and a small lamp (the load) to which the free ends of the wires leading from the cell are attached. When the connections are made properly, current flows, the circuit is said to be "closed," and the lamp will light. The current flows from the cell along one wire to the lamp, through the lamp, and along the other wire back to the cell. When the wires are disconnected, the circuit is said to be "open" or "broken." In practice, circuits are opened by such devices as switches, fuses, and circuit breakers (see fuse, electric; circuit breaker; short circuit). Two general circuit classifications are series and parallel. The elements of a series circuit are connected end to end; the same current flows through its parts one after another. The elements of a parallel circuit are connected so that each component has the same voltage across its terminals; the current flow is divided among its parts. When two circuit elements are connected in series, their effective resistance (impedance if the circuit is being fed alternating current) is equal to the sum of the separate resistances; the current is the same in each component throughout the circuit. When circuit elements are connected in parallel, the total resistance is less than that of the element having the least resistance, and the total current is equal to the sum of the currents in the individual branches. A battery-powered circuit is an example of a direct-current circuit; the voltages and currents are constant in magnitude and do not vary with time. In alternating-current circuits, the voltage and current periodically reverse direction with time. A standard electrical outlet supplies alternating current. Lighting circuits and electrical machinery use alternating current circuits. Many other devices, including computers, stereo systems, and television sets, must first convert the alternating current to direct current. That is done by a special internal circuit usually called a power supply. A digital circuit is a special kind of electronic circuit used in computers and many other devices. Magnetic circuits are analogous to electric circuits, where magnetic materials are regarded as conductors of magnetic flux. Magnetic circuits can be part of an electric circuit; a transformer is an example. Equivalent circuits are used in circuit analysis as a modeling tool; a simple circuit made up of a resistor, and an inductor might be used to electrically represent a loudspeaker. Electrical circuits can also be used in other fields of studies. In the study of heat flow, for example, a resistor is used to represent thermal insulation. Operating electric circuits can be used for general problem solving (as in an analog computer).

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circuit, electric

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series circuit

series circuit: see electric circuit.

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Electric Circuit

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 (17451847) 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 (17871854) 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.

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Electric Circuit

Electric circuit

An electric circuit is a system of conducting elements designed to control the path of electric current for a particular purpose. Circuits consist of sources of electric energy , like 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 prevent a power overload.

Devices that are connected to a circuit are connected to it in one of two ways: in series or in parallel . A series circuit forms a single pathway for the flow of current, while a parallel circuit forms separate paths or branches for the flow of current. Parallel circuits have an important advantage over series circuits. If a device connected to a series circuit malfunctions or is switched off, the circuit is broken, and other devices on the circuit cannot draw power. The separate pathways of a parallel circuit allows devices to operate independently of each other, maintaining the circuit even if one or more devices are switched off.

The first electric circuit was invented by Alessandro Volta 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 in an electrical circuit, which is often not wanted.

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

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