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Current Balance
The ampere balance (also current balance or Kelvin balance) is an electromechanical apparatus used for the accuracy and precision, precise measurement of the SI unit of electric current, the ampere. It was invented by William Thomson, 1st Baron Kelvin. The current to be measured is passed in series through two coils of wire, one of which is attached to one arm of a sensitive Weighing scale, balance. The magnetic force between the two coils is measured by the amount of weight needed on the other arm of the balance to keep it in equilibrium. This is used to calculate the numerical value of the current. The main weakness of the ampere balance is that the calculation of the current involves the dimensions of the coils. So the accuracy of the current measurement is limited by the accuracy with which the coils can be measured, and their mechanical rigidity. A more complicated version of an ampere balance, that removes this source of inaccuracy by a calibration step, is the Kib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Bureau Of Standards
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical science laboratory programs that include nanoscale science and technology, engineering, information technology, neutron research, material measurement, and physical measurement. From 1901 to 1988, the agency was named the National Bureau of Standards. History Background The Articles of Confederation, ratified by the colonies in 1781, provided: The United States in Congress assembled shall also have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States. Article 1, section 8, of the Constitution of the United States, ratified in 1789, granted these powers to the new Con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kibble Balance
A Kibble balance (also formerly known as a watt balance) is an electromechanical measuring instrument that measures the weight of a test object very precisely by the electric current and voltage needed to produce a compensating force. It is a Metrology, metrological instrument that can realize the definition of the kilogram unit of mass based on Physical constant, fundamental constants. It was originally known as a watt balance because the weight of the test mass is proportional to the product of current and voltage, which is measured in watts. In June 2016, two months after the death of its inventor, Bryan Kibble, metrologists of the Consultative Committee for Units of the International Committee for Weights and Measures agreed to rename the device in his honor. Prior to 2019, the definition of the kilogram was based on a physical object known as the International Prototype of the Kilogram (IPK). Alternative approaches to redefining the kilogram, After considering alternative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Couple (mechanics)
In physics, a couple or torque is a pair of forces that are equal in magnitude but opposite in their direction of action. A couple produce a pure Rotation, rotational motion without any Translation, translational form. Simple couple The simplest kind of couple consists of two equal and opposite forces whose line of action, lines of action do not coincide. This is called a "simple couple".''Dynamics, Theory and Applications'' by T.R. Kane and D.A. Levinson, 1985, pp. 90–99Free download/ref> The forces have a turning effect or moment called a torque about an axis which is normal (geometry), normal (perpendicular) to the plane of the forces. The SI unit for the torque of the couple is newton metre. If the two forces are and , then the Euclidean vector, magnitude of the torque is given by the following formula: \tau = F d where *\tau is the moment of couple * is the magnitude of the force * is the perpendicular distance (moment) between the two parallel forces The magnitude of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Square Root
In mathematics, a square root of a number is a number such that y^2 = x; in other words, a number whose ''square'' (the result of multiplying the number by itself, or y \cdot y) is . For example, 4 and −4 are square roots of 16 because 4^2 = (-4)^2 = 16. Every nonnegative real number has a unique nonnegative square root, called the ''principal square root'' or simply ''the square root'' (with a definite article, see below), which is denoted by \sqrt, where the symbol "\sqrt" is called the '' radical sign'' or ''radix''. For example, to express the fact that the principal square root of 9 is 3, we write \sqrt = 3. The term (or number) whose square root is being considered is known as the ''radicand''. The radicand is the number or expression underneath the radical sign, in this case, 9. For non-negative , the principal square root can also be written in exponent notation, as x^. Every positive number has two square roots: \sqrt (which is positive) and -\sqrt (which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equilibrium
Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibrium'', short film by Steven Soderbergh, a segment of ''Eros'' * "Equilibrium" (''Star Trek: Deep Space Nine''), Star Trek DS9 Episode 4, Season 3 Music * Equilibrium (band), a folk metal band from Germany * ''Equilibrium'' (Crowbar album), 2000 * ''Equilibrium'' (Erik Mongrain album), 2008 * ''Equilibrium'' (God Forbid album), 2012 * ''Equilibrium'' (Whitecross album), 1995 * ''Equilibrium'' (Matthew Shipp album), 2003 * '' IX Equilibrium'', a 1999 album by Emperor * ''Equilibrium'', an album by Fergie Frederiksen Natural sciences * Chemical equilibrium * Equilibrium chemistry * Equilibrium point of differential equations * Mechanical equilibrium * Thermodynamic equilibrium Social sciences * Cognitive equilibration in psych ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slider Of Kelvin Ampere Balance
Slider or Sliders may refer to: Arts * K.K. Slider, a fictional character within the ''Animal Crossing'' franchise * '' The Slider'', a 1972 album by T. Rex * ''Sliders'' (TV series), an American science fiction and fantasy television series * Slider, a recurring character in the animated television series ''Cyberchase'' Sports * Slider (cricket), a type of delivery bowled by a wrist spin bowler * Slider (pitch), a breaking ball pitch in baseball * Slider, mascot for the Major League Baseball team Cleveland Indians/Guardians Technology * Slider (BEAM), a robot that has a mode of locomotion by moving body parts smoothly along a surface * Slider (computing), a graphical control element with which a user may set a value by moving an indicator * Slider (mobile phones), a form factor of mobile phones * Slider, a type of potentiometer Other uses * '' Lerista'' (also sliders), a diverse genus of skinks endemic to Australia * Slide (footwear) (also sliders), a type of light fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2019 Revision Of The SI
In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants, rather than human artefacts such as the standard kilogram. Effective 20 May 2019, the 144th anniversary of the Metre Convention, the kilogram, ampere, kelvin, and mole are defined by setting exact numerical values, when expressed in SI units, for the Planck constant ('), the elementary electric charge ('), the Boltzmann constant (), and the Avogadro constant (), respectively. The second, metre, and candela had previously been redefined using physical constants. The four new definitions aimed to improve the SI without changing the value of any units, ensuring continuity with existing measurements. In November 2018, the 26th General Conference on Weights and Measures (CGPM) unanimously approved these changes, The conference ran from 13–16 November and the vote on the redefinition was scheduled for the last day. Kazakhstan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Prototype Of The Kilogram
The International Prototype of the Kilogram (referred to by metrology, metrologists as the IPK or Le Grand K; sometimes called the ''wiktionary:ur-#Prefix, ur-kilogram'', or ''urkilogram'', particularly by German-language authors writing in English) is an object whose mass was used to define the kilogram from 1889, when it replaced the ''Kilogramme des Archives'', until 2019, when it was replaced by a 2019 revision of the SI, new definition of the kilogram based entirely on physical constants. During that time, the IPK and its duplicates were used to calibrate all other kilogram mass standards on Earth. The IPK is a roughly golfball-sized object made of a platinum–iridium alloy known as "Pt10Ir", which is 90% platinum and 10% iridium (by mass) and is machined into a right-circular cylinder with perpendicular height equal to its diameter of about 39millimetres to reduce its surface area. The addition of 10% iridium improved upon the all-platinum ''Kilogramme des Archives'' by g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physics. It was found that different atoms and different elementary particle, elementary particles, theoretically with the same amount of matter, have nonetheless different masses. Mass in modern physics has multiple Mass in special relativity, definitions which are conceptually distinct, but physically equivalent. Mass can be experimentally defined as a measure (mathematics), measure of the body's inertia, meaning the resistance to acceleration (change of velocity) when a net force is applied. The object's mass also determines the Force, strength of its gravitational attraction to other bodies. The SI base unit of mass is the kilogram (kg). In physics, mass is Mass versus weight, not the same as weight, even though mass is often determined by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilogram
The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (meaning one thousand) and gram; it is colloquially shortened to "kilo" (plural "kilos"). The kilogram is an SI base unit, defined ultimately in terms of three defining constants of the SI, namely a specific transition frequency of the caesium-133 atom, the speed of light, and the Planck constant. A properly equipped metrology laboratory can calibrate a mass measurement instrument such as a Kibble balance as a primary standard for the kilogram mass. The kilogram was originally defined in 1795 during the French Revolution as the mass of one litre of water (originally at 0 °C, later changed to the temperature of its maximum density, approximately 4 °C). The current definition of a kilogram agrees with this original defini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metrology
Metrology is the scientific study of measurement. It establishes a common understanding of Unit of measurement, units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France when a length standard taken from a natural source was proposed. This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements. Several other countries adopted the metric system between 1795 and 1875; to ensure conformity between the countries, the ''International Bureau of Weights and Measures, Bureau International des Poids et Mesures'' (BIPM) was established by the Metre Convention. This has evolved into the International System of Units (SI) as a result of a resolution at the 11th General Conference on Weights and Measures (CGPM) in 1960. Metrology is divided into three basic overlapping activities: * The definition of units of measurement * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bryan Kibble
Bryan Peter Kibble (20 October 1938 – 28 April 2016) was a British physicist and a pioneering metrologist. He was the inventor of the Kibble balance, an improved version of the current balance, developed for the realisation of the S.I. unit of mass, the kilogram. Early years and family Kibble was born in Letcombe Regis (formerly in Berkshire, now part of Oxfordshire) to Ellen and Herbert Kibble. His father was a police sergeant. He was the youngest of four children. From an early age he enjoyed repairing electrical and mechanical devices. He attended Abingdon School from 1950 to 1957, where he was a house prefect and gained significant academic success. He won numerous prizes for physics, mathematics and science and was awarded a Bennett Scholarship. He was a member of the Debating and Roysse Society in addition to playing for the hockey and rugby teams. He was awarded an open scholarship to study Natural Science at Jesus College, Oxford. He met his future wife, Anne Green ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
