Capacitor Wikipedia. This article is about the electrical component. For the physical phenomenon, see capacitance. For an overview of various kinds of capacitors, see types of capacitor. Capacitive redirects here. For the term used when referring to touchscreens, see capacitive sensing. A capacitor is a passivetwo terminalelectrical component that stores electrical energy in an electric field. 1 The effect of a capacitor is known as capacitance. While capacitance exists between any two electrical conductors of a circuit in sufficiently close proximity, a capacitor is specifically designed to provide and enhance this effect for a variety of practical applications by consideration of size, shape, and positioning of closely spaced conductors, and the intervening dielectric material. A capacitor was therefore historically first known as an electric condenser. 2The physical form and construction of practical capacitors vary widely and many capacitor types are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitors charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy. When two conductors experience a potential difference, for example, when a capacitor is attached 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. No current actually flows through the dielectric, however, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. However, 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. Capacitance is defined as the ratio of the electric charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units SI is the farad F, defined as one coulomb per volt 1 CV. Capacitance values of typical capacitors for use in general electronics range from about 1 p. F 1. 01. 2 F to about 1 m. F 1. 03 F. The capacitance of a capacitor is proportional to the surface area of the plates conductors and inversely related to the gap between them. In practice, the dielectric between the plates passes a small amount of leakage current. It has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance. Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage and power flow. 3 The property of energy storage in capacitors was exploited as dynamic memory in early digital computers. 4HistoryeditIn October 1. 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. 5 Von Kleists hand and the water acted as conductors, and the jar as a dielectric although details of the mechanism were incorrectly identified at the time. Von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine. 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. 6 He also was impressed by the power of the shock he received, writing, I would not take a second shock for the kingdom of France. 7Benjamin Franklin investigated the Leyden jar and came to the conclusion that the charge was stored on the glass, not in the water as others had assumed. He also adopted the term battery,89 denoting the increasing of power with a row of similar units as in a battery of cannon, subsequently applied to clusters of electrochemical cells. 1. Leyden jars were later made by coating the inside and outside of jars with metal foil, leaving a space at the mouth to prevent arcing between the foils. citation needed The earliest unit of capacitance was the jar, equivalent to about 1. Leyden jars or more powerful devices employing flat glass plates alternating with foil conductors were used exclusively up until about 1. More compact construction methods began to be used, such as a flexible dielectric sheet like oiled paper sandwiched between sheets of metal foil, rolled or folded into a small package. Early capacitors were known as condensers, a term that is still occasionally used today, particularly in high power applications, such as automotive systems. The term was first used for this purpose by Alessandro Volta in 1. The term became deprecated because of the ambiguous meaning of steam condenser, with capacitor becoming the recommended term from 1. Since the beginning of the study of electricity non conductive materials like glass, porcelain, paper and mica have been used as insulators. These materials some decades later were also well suited for further use as the dielectric for the first capacitors. Paper capacitors made by sandwiching a strip of impregnated paper between strips of metal, and rolling the result into a cylinder were commonly used in the late 1. Porcelain was used in the first ceramic capacitors. In the early years of Marconis wireless transmitting apparatus porcelain capacitors were used for high voltage and high frequency application in the transmitters. On the receiver side smaller mica capacitors were used for resonant circuits. Mica dielectric capacitors were invented in 1. William Dubilier. Prior to World War II, mica was the most common dielectric for capacitors in the United States. 1. Charles Pollak born Karol Pollak, the inventor of the first electrolytic capacitors, found out that the oxide layer on an aluminum anode remained stable in a neutral or alkaline electrolyte, even when the power was switched off. In 1. 89. 6 he was granted U. S. Patent No. 6. 72,9. Electric liquid capacitor with aluminum electrodes. Solid electrolyte tantalum capacitors were invented by Bell Laboratories in the early 1. With the development of plastic materials by organic chemists during the Second World War, the capacitor industry began to replace paper with thinner polymer films. One very early development in film capacitors was described in British Patent 5. Last but not least the electric double layer capacitor now Supercapacitors were invented. In 1. 95. 7 H. Becker developed a Low voltage electrolytic capacitor with porous carbon electrodes. 1. He believed that the energy was stored as a charge in the carbon pores used in his capacitor as in the pores of the etched foils of electrolytic capacitors. Because the double layer mechanism was not known by him at the time, he wrote in the patent It is not known exactly what is taking place in the component if it is used for energy storage, but it leads to an extremely high capacity. Theory of operationeditOverviewedit. Charge separation in a parallel plate capacitor causes an internal electric field. A dielectric orange reduces the field and increases the capacitance. A simple demonstration capacitor made of two parallel metal plates, using an air gap as the dielectric. A capacitor consists of two conductors separated by a non conductive region. 1. The non conductive region can either be a vacuum or an electrical insulator material known as a dielectric. Examples of dielectric media are glass, air, paper, and even a semiconductordepletion region chemically identical to the conductors. A capacitor is assumed to be self contained and isolated, with no net electric charge and no influence from any external electric field. The conductors thus hold equal and opposite charges on their facing surfaces,1. Peer Reviewed Journal. Abstract Nanoparticles synthesis by biological. In this research, Silver. Ag NPs were synthesized from. Ag. NO3 solution by green synthesis process with. The. detailed characterization of the Ag NPs were. UV visible spectroscopy. Scanning electron microscopy SEM, Energy. X ray Spectroscopy EDS, Dynamic. DLS analysis, and their. Escherichia coli. The UV visible spectroscopy. The DLS analysis. SEM. analysis showed the morphology of. The elemental composition of. EDS. analysis. Antibacterial assay of synthesized Ag. NP was carried out in solid Nutrient Agar. E. coli. The presence of. Key words MAntibacterial assay, eco friendly. Reference1 Kim, S. W., Nam, S. H. and An, Y. J. Interaction of silver nanoparticles with. Caenorhabditis. elegans. Ecotoxicol Environ Saf, 7. Hussain, S. M., Hess, K. L., Gearhart, J. M. Geiss, K. T. and Schlager, J. J., In vitro. toxicity of nanoparticles in BRL 3. A rat. liver cells. Toxicol In Vitro, 1. Premanathan, M., Karthikeyan, K. Jeyasubramanian, K. Manivannan, G. Selective toxicity of Zn. O nanoparticles. toward Gram positive bacteria and cancer. Nanomedicine, 7 2, 2. Srivastava, M., Singh, S. Self, W. T. Exposure to silver nanoparticles inhibits. Environ Health. Perspect, 1. Nagy, A., Harrison, A., Sabbani, S. Munson, R. S., Jr., Dutta, P. K. and. Waldman, W. J., Silver nanoparticles. Int J Nanomedicine, 6, 2. Bhumkar, D. R., Joshi, H. M., Sastry, M. and Pokharkar, V. B., Chitosan reduced. Pharm. Res, 2. 4 8, 2. Arunachalam, R., Dhanasingh, S. Kalimuthu, B., Uthirappan, M., Rose, C. Mandal, A. B., Phytosynthesis of silver. Coccinia grandis leaf. Colloids Surf B. Biointerfaces, 9. Patil, R. S., Kokate, M. R. and Kolekar, S. S. Bioinspired synthesis of highly stabilized. Ocimum. tenuiflorum leaf extract and their. Spectrochim Acta A. Mol Biomol Spectrosc, 9. C, 2. 01. 1, 2. 34. Kumar, R., Roopan, S. M., Prabhakarn, A. Khanna, V. G. and Chakroborty, S. Agricultural waste Annona squamosa peel. Biosynthesis of silver. Spectrochim Acta A Mol. Biomol Spectrosc, 9. Natrajan, Kannan, Subbalaxmi Selvaraj. V. R. Ramamurthy. Microbial. production of silver nanoparticles. Digest. Journal of Nanomaterials and. Biostructures 51, 2.
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