![]() The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor, which was named the Leyden jar, after the University of Leiden where he worked. Von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine. Von Kleist's hand and the water acted as conductors and the jar as a dielectric (although details of the mechanism were incorrectly identified at the time). In October 1745, Ewald Georg von Kleist of Pomerania, Germany, found that charge could be stored by connecting a high-voltage electrostatic generator by a wire to a volume of water in a hand-held glass jar. See also: Leyden jar Battery of four Leyden jars in Museum Boerhaave, Leiden, the Netherlands The property of energy storage in capacitors was exploited as dynamic memory in early digital computers, and still is in modern DRAM. In electric power transmission systems, they stabilize voltage and power flow. In resonant circuits they tune radios to particular frequencies. In analog filter networks, they smooth the output of power supplies. Today, capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. The earliest forms of capacitors were created in the 1740s, when European experimenters discovered that electric charge could be stored in water-filled glass jars that came to be known as Leyden jars. If a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor. If the condition is maintained sufficiently long, the current through the source circuit ceases. However, there is a flow of charge through the source circuit. No current actually flows through the dielectric. When an electric potential difference (a voltage) is applied across the terminals of a capacitor, for example when a capacitor is connected across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate. ![]() Unlike a resistor, an ideal capacitor does not dissipate energy, although real-life capacitors do dissipate a small amount (see Non-ideal behavior). Capacitors are widely used as parts of electrical circuits in many common electrical devices. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, air, and oxide layers. The nonconducting dielectric acts to increase the capacitor's charge capacity. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. Most capacitors contain at least two electrical conductors, often in the form of metallic plates or surfaces separated by a dielectric medium. The physical form and construction of practical capacitors vary widely and many types of capacitor are in common use. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the condenser microphone. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The effect of a capacitor is known as capacitance. It is a passive electronic component with two terminals. For the term used when referring to touchscreens, see Capacitive sensing.Įwald Georg von Kleist, Pieter van Musschenbroek 1745 278 years ago ( 1745) (independently)Ī capacitor is an electronic device that stores electrical energy in an electric field by accumulating electric charges on two closely spaced surfaces that are insulated from each other.
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