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Electret Microphone
An electret microphone is a microphone whose diaphragm forms a capacitor (historically-termed a ''condenser'') that incorporates an electret. The electret's permanent electric dipole provides a constant charge on the capacitor. Sound waves move the diaphragm, changing the capacitance , which produces a corresponding voltage change across the capacitor of . The electret's constant charge eliminates the need for the polarizing power supply required for non-electret condenser microphones, though a preamplifier is typically incorporated to boost the audio voltage signal. Electret material An ''electret'' is a stable dielectric material with a permanently-embedded electric dipole that persists for hundreds of years due to its high resistance and chemical stability. The name comes from ''electr''ostatic and magn''et''; drawing analogy to the formation of a magnet by alignment of magnetic domains in a piece of iron. Electrets are commonly made by first melting a suitable die ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electret Condenser Microphone Capsules
An electret (formed as a portmanteau of ''electr-'' from "electricity" and ''-et'' from "magnet") is a dielectric material that has a quasi-permanent electrical polarisation. An electret has internal and external electric fields, and is the electrostatic equivalent of a permanent magnet. The term electret was coined by Oliver Heaviside for a (typically dielectric) material which has electrical charges of opposite sign at its extremities. Some materials with electret properties were already known to science and had been studied since the early 1700s. One example is the electrophorus, a device consisting of a slab with electret properties and a separate metal plate. The electrophorus was originally invented by Johan Carl Wilcke in Sweden in 1762 and improved by Alessandro Volta in Italy in 1775. The first documented case of production was by Mototarô Eguchi in 1925 who melting a suitable dielectric material such as a polymer or wax that contains polar molecules, and then allowin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (), while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ). The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductance, while objects made of electrical conductors like metals tend to have very low resistance and high conductance. This relationship is quantified by resistivity or conductivity. The nature of a material is not the only factor in resistance and conductance, however; it also depends on the size and shape of an object because these properties are extensive rather tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Society Of Chemistry
The Royal Society of Chemistry (RSC) is a learned society and professional association in the United Kingdom with the goal of "advancing the chemistry, chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society, and the Society for Analytical Chemistry with a new Royal Charter and the dual role of learned society and professional body. At its inception, the Society had a combined membership of 49,000 in the world. The headquarters of the Society are at Burlington House, Piccadilly, London. It also has offices in Thomas Graham House in Cambridge (named after Thomas Graham (chemist), Thomas Graham, the first president of the Chemical Society) where ''RSC Publishing'' is based. The Society has offices in the United States, on the campuses of The University of Pennsylvania and Drexel University, at the University City Science Center in Philadelphia, Pennsylvania, in both Beijing and Shanghai, People' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry World
''Chemistry World'' is a monthly chemistry news magazine published by the Royal Society of Chemistry. The magazine addresses current events in the world of chemistry including research, international business news and government policy as it affects the chemical science community, plus the best product applications. It features regular columns by Philip Ball, Derek Lowe (chemist), Derek Lowe, Andrea Sella, Raychelle Burks, Alice Motion and Vanessa Seifert. The magazine is sent to all members of the Royal Society of Chemistry and is included in the cost of membership. In August 2016, the magazine began offering a "soft" paywall option, where a limited amount of content is made available free to all unregistered readers. History In 1965 two British chemistry institutions, the Chemical Society and the Royal Institute of Chemistry agreed to merge their primary publications ''Proceedings of the Chemical Society'' and the ''Journal of the Royal Institute of Chemistry''. This was a fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teflon
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally invented the compound in 1938. Polytetrafluoroethylene is a fluorocarbon solid, as it is a high- molecular-weight polymer consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid. Polytetrafluoroethylene is used as a non-stick coating for pans and other cookware. It is non-reactive, partly because of the strength of carbon–fluorine bonds, so it is often used in containers and pipework for reactive and corrosive chemicals. When used as a lubricant, PTFE reduces fric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James West (inventor)
James Edward Maceo West (born February 10, 1931) is an American inventor and acoustician. He holds over 250 foreign and U.S. patents for the production and design of microphones and techniques for creating polymer foil electrets. Early life West was born on February 10, 1931, in Farmville, Prince Edward County, Virginia as the elder of two children to Samuel Edward and Matilda West. He was born in his maternal grandfather's house because the local hospital would not admit Black people. His father worked at various points as a funeral home owner, an insurance salesman, and as a Pullman porter on the Baltimore and Ohio Railroad. His mother was a schoolteacher who worked at Langley Air Force Base during World War II; she later lost her job due to her involvement in the NAACP and became one of the "Hidden Figures" (Black astrophysicists who worked for NASA at Langley Research Center and received little to no credit for their work). His maternal grandmother, who was formerly en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gerhard Sessler
Gerhard M. Sessler (born 15 February 1931 in Rosenfeld, Baden-Württemberg, Germany) is a German inventor and scientist. He is Professor emeritus at the Department of Electrical Engineering and Information Technology of the Technische Universität Darmstadt. Together with James E. West, he invented the foil electret microphone at Bell Laboratories in 1962. Together with Dietmar Hohm, he invented the MEMS microphone, also known as the silicon microphone in 1983. Life From 1950 to 1959, Sessler studied physics at Universities of Freiburg, Munich, and Göttingen. He received his diploma in 1957 and his Ph.D. from the University of Göttingen in 1959. After working in the United States at Bell Labs until 1975, he returned to the academia in Germany. From 1975 to 2000, he worked as a professor of electrical engineering at the Department of Electrical Engineering and Information Technology of the Technische Universität Darmstadt where he invented the silicon microphone. In 199 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Laboratories
Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several laboratories in the United States and around the world. As a former subsidiary of the American Telephone and Telegraph Company (AT&T), Bell Labs and its researchers have been credited with the development of radio astronomy, the transistor, the laser, the photovoltaic cell, the charge-coupled device (CCD), information theory, the Unix operating system, and the programming languages B, C, C++, S, SNOBOL, AWK, AMPL, and others, throughout the 20th century. Eleven Nobel Prizes and five Turing Awards have been awarded for work completed at Bell Laboratories. Bell Labs had its origin in the complex corporate organization of the Bell System telephone conglomerate. The laboratory began operating in the late 19th century as the Wester ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Condenser Microphone
A microphone, colloquially called a mic (), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors. Several types of microphone are used today, which employ different methods to convert the air pressure variations of a sound wave to an electrical signal. The most common are the dynamic microphone, which uses a coil of wire suspended in a magnetic field; the condenser microphone, which uses the vibrating diaphragm as a capacitor plate; and the contact microphone, which uses a crystal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Field
An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) describes their capacity to exert attractive or repulsive forces on another charged object. Charged particles exert attractive forces on each other when the sign of their charges are opposite, one being positive while the other is negative, and repel each other when the signs of the charges are the same. Because these forces are exerted mutually, two charges must be present for the forces to take place. These forces are described by Coulomb's law, which says that the greater the magnitude of the charges, the greater the force, and the greater the distance between them, the weaker the force. Informally, the greater the charge of an object, the stronger its electric field. Similarly, an electric field is stronger nearer charged objects and weaker f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrostatic
Electrostatics is a branch of physics that studies slow-moving or stationary electric charges. Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word (), meaning 'amber', was thus the root of the word ''electricity''. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb's law. There are many examples of electrostatic phenomena, from those as simple as the attraction of plastic wrap to one's hand after it is removed from a package, to the apparently spontaneous explosion of grain silos, the damage of electronic components during manufacturing, and photocopier and laser printer operation. The electrostatic model accurately predicts electrical phenomena in "classical" cases where the velocities are low and the system is macroscopic so no quantum effects are involved. It also plays a role in quantum mechanics, where addition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecules
A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and ''molecule'' is often used when referring to polyatomic ions. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O). In the kinetic theory of gases, the term ''molecule'' is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
