This article is about the electronic component. For the physical phenomenon, see capacitance. For an overview of variouskinds of capacitors, see types of capacitor.
Modern capacitors, by a cm rule
Invented Ewald Georg von Kleist (October 1745)
A typicalelectrolytic capacitorA capacitor (formerly known as condenser) is a device for storing electric charge. The forms of practical capacitors vary widely, but all contain at least two conductors separated bya non-conductor. Capacitors used as parts of electrical systems, for example, consist of metal foils separated by a layer of insulating film.
A capacitor is a passive electronic componentconsisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric, causingpositive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value,capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.
Capacitors are widely used in electronic circuits for blocking directcurrent while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies and for many otherpurposes.
The capacitance is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called "plates", referring to an early means ofconstruction. In practice the dielectric between the plates passes a small amount of leakage current and also has an electric field strength limit, resulting in a breakdown voltage, while the conductors...