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Volt The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force.[1] It is named after the Italian physicist Alessandro Volta (1745–1827).Contents1 Definition1.1 Josephson junction definition2 Waterflow analogy 3 Common voltages 4 History 5 See also 6 References 7 External linksDefinition[edit] One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.[2] It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it [...More...]  "Volt" on: Wikipedia Yahoo 

Caesium Standard The caesium standard is a primary frequency standard in which electronic transitions between the two hyperfine ground states of caesium133 atoms are used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.[1] and promoted worldwide by Gernot M. R. Winkler of the USNO. Caesium atomic clocks are the most accurate time and frequency standards, and serve as the primary standard for the definition of the second in the International System of Units (SI) (the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth's magnetic field) has a frequency of exactly 9,192,631,770 Hz [...More...]  "Caesium Standard" on: Wikipedia Yahoo 

Electrochemical Cell An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5  volt[1] cell meant for consumer use. This type of device is known as a single galvanic cell. A battery consists of one or more cells, connected in either parallel or series pattern.[2]Contents1 Halfcells1.1 Equilibrium reaction 1.2 Cell potential2 See also 3 ReferencesHalfcells[edit]The Bunsen cell, invented by Robert Bunsen.An electrochemical cell consists of two halfcells. Each halfcell consists of an electrode and an electrolyte. The two halfcells may use the same electrolyte, or they may use different electrolytes. The chemical reactions in the cell may involve the electrolyte, the electrodes, or an external substance (as in fuel cells that may use hydrogen gas as a reactant) [...More...]  "Electrochemical Cell" on: Wikipedia Yahoo 

Junction (semiconductor) An electrical junction may be either a thermoelectricity junction, a metal–semiconductor junction or a p–n junction (ptype semiconductor–ntype semiconductor junction). Junctions are either rectifying or nonrectifying. Nonrectifying junctions are called ohmic contacts [...More...]  "Junction (semiconductor)" on: Wikipedia Yahoo 

Pressure Pressure Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the ambient pressure. Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit SI unit of pressure, the pascal (Pa), for example, is one newton per square metre; similarly, the poundforce per square inch (psi) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this [...More...]  "Pressure" on: Wikipedia Yahoo 

Energy In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.[note 1] Energy Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton. Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature. Mass Mass and energy are closely related [...More...]  "Energy" on: Wikipedia Yahoo 

Elementary Charge The elementary charge, usually denoted as e or sometimes q, is the electric charge carried by a single proton, or equivalently, the magnitude of the electric charge carried by a single electron, which has charge −e.[2] This elementary charge is a fundamental physical constant. To avoid confusion over its sign, e is sometimes called the elementary positive charge. This charge has a measured value of approximately 6981160217662079999♠1.6021766208(98)×10−19 coulombs,[1] and after the planned redefinition of SI base units in 20182019, its value will be exactly 1.602176634×10−19C by definition of the Coulomb [...More...]  "Elementary Charge" on: Wikipedia Yahoo 

Flux Flux Flux describes the quantity which passes through a surface or substance. A flux is either a concept based in physics or used with applied mathematics. Both concepts have mathematical rigor, enabling comparison of the underlying math when the terminology is unclear. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property [...More...]  "Flux" on: Wikipedia Yahoo 

NIST The National Institute of Standards and Technology Technology (NIST) is a measurement standards laboratory, and a nonregulatory agency of the United States Department of Commerce [...More...]  "NIST" on: Wikipedia Yahoo 

Metre The metre (British spelling and BIPM spelling[1]) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units International System of Units (SI). The SI unit symbol is m.[2] The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 second.[1] The metre was originally defined in 1793 as one tenmillionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton86. In 1983, the current definition was adopted. The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about 3 3⁄8 inches longer than a yard, i.e [...More...]  "Metre" on: Wikipedia Yahoo 

Second The second is the SI base unit SI base unit of time, commonly understood and historically defined as 1/86,400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Another intuitive understanding is that it is about the time between beats of a human heart.[nb 1] Mechanical and electric clocks and watches usually have a face with 60 tickmarks representing seconds and minutes, traversed by a second hand and minute hand. Digital clocks and watches often have a twodigit counter that cycles through seconds [...More...]  "Second" on: Wikipedia Yahoo 

System Of Measurement A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Systems of measurement in modern use include the metric system, the imperial system, and United States United States customary units.Contents1 History1.1 Current practice2 Metric system 3 Imperial and US customary units 4 Natural units 5 Nonstandard units5.1 Area 5.2 Energy6 Units of currency 7 Historical systems of measurement7.1 Africa 7.2 Asia 7.3 Europe 7.4 North America 7.5 Oceania 7.6 South America8 See also8.1 Conversion tables9 Notes and references 10 Bibliography 11 External linksHistory[edit] Main article: History of measurement The French Revolution French Revolution gave rise to the metric system, and this has spread around the world, replacing most customary units of measure [...More...]  "System Of Measurement" on: Wikipedia Yahoo 

Hagen–Poiseuille Equation In nonideal fluid dynamics, the Hagen–Poiseuille equation, also known as the Hagen–Poiseuille law, Poiseuille law or Poiseuille equation, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section. It can be successfully applied to air flow in lung alveoli, or the flow through a drinking straw or through a hypodermic needle. It was experimentally derived independently by Jean Léonard Marie Poiseuille Jean Léonard Marie Poiseuille in 1838[1] and Gotthilf Heinrich Ludwig Hagen,[2] and published by Poiseuille in 1840–41 and 1846.[1] The assumptions of the equation are that the fluid is incompressible and Newtonian; the flow is laminar through a pipe of constant circular crosssection that is substantially longer than its diameter; and there is no acceleration of fluid in the pipe [...More...]  "Hagen–Poiseuille Equation" on: Wikipedia Yahoo 

SI Base Unit The International System of Units International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the metre for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter [...More...]  "SI Base Unit" on: Wikipedia Yahoo 

Meter The metre (British spelling and BIPM spelling[1]) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units International System of Units (SI). The SI unit symbol is m.[2] The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 second.[1] The metre was originally defined in 1793 as one tenmillionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton86. In 1983, the current definition was adopted. The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about 3 3⁄8 inches longer than a yard, i.e [...More...]  "Meter" on: Wikipedia Yahoo 

General Conference On Weights And Measures The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM) is the senior of the three Intergovernmental organizations Intergovernmental organizations established in 1875 under the terms of the Metre Convention Metre Convention (French: Convention du Mètre) to represent the interests of member states. The treaty, which also set up two further bodies, the International Committee for Weights and Measures (French: Comité international des poids et mesures – CIPM) and the International Bureau of Weights and Measures International Bureau of Weights and Measures (French: Bureau international des poids et mesures – BIPM), was drawn up to coordinate international metrology and to coordinate the development of the metric system. The conference meets in Sèvres Sèvres (southwest of Paris) every four to six years [...More...]  "General Conference On Weights And Measures" on: Wikipedia Yahoo 