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Topic: SI base unit


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SI

In the News (Wed 17 Apr 19)

  
  SI base unit - Wikipedia, the free encyclopedia
The unit of mass is equal to the mass of the international prototype kilogram (a platinum-iridium cylinder) kept at the Bureau International des Poids et Mesures (BIPM), Sèvres, Paris (1st CGPM (1889), CR 34-38).
The unit of time is the duration of exactly 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium-133 atom at a temperature of 0 K (13th CGPM (1967-1968) Resolution 1, CR 103).
The unit of length is equal to the length of the path travelled by light in a vacuum during the time interval of 1/299 792 458 of a second (17th CGPM (1983) Resolution 1, CR 97).
en.wikipedia.org /wiki/SI_base_unit   (465 words)

  
 SI - Wikipedia, the free encyclopedia
Based on the findings of this study, the 10th CGPM in 1954 decided that an international system should be derived from six base units to provide for the measurement of temperature and optical radiation in addition to mechanical and electromagnetic quantities.
The six base units recommended were the metre, kilogram, second, ampere, Kelvin degree (later renamed the kelvin), and the candela.
Since most non-SI units, such as the U.S. customary units, are nowadays defined in terms of SI units, any change in the definition of the SI units results in a change of the definition of the older units as well.
en.wikipedia.org /wiki/SI   (1682 words)

  
 SI - Simple English Wikipedia
Unit: ampere (A) The ampere is that constant electrical current (or flow) which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10
Unit: kelvin (K) The kelvin, unit of temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
The candela is one of two base units (the other being the ampere) that is not defined purely in terms of base units.
simple.wikipedia.org /wiki/SI_base_unit   (616 words)

  
 Encyclopedia: SI
SI is built on seven SI base units, such as the kilogram and metre.
SI is built on seven SI base units, the kilogram, metre, second, ampere, kelvin, mole, and candela.
The unit of angle is the angle subtended at the centre of a circle by an arc of the circumference equal in length to the radius of the circle.
www.nationmaster.com /encyclopedia/SI   (608 words)

  
 Encyclopedia: SI base unit
SI derived units are part of the SI system of measurement units and are derived from the seven SI base units.
The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units.
The hertz (symbol Hz) is the SI unit of frequency.
www.nationmaster.com /encyclopedia/SI-base-unit   (1576 words)

  
 Station Information - SI base unit
One second is defined as the time required for 9192631770 cycles of the transition between the two hyperfine levels of the ground state of caesium 133.
Unit: ampere (A) The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10
Unit: Kelvin (K) The Kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
www.stationinformation.com /encyclopedia/s/si/si_base_unit.html   (306 words)

  
 Definitions of the SI Units and other Units of Measurement
The SI derived unit for the mass of a mole of substance and is measured in kilogram per mole.
The SI unit of radiation dose is the gray (Gy); one rad equals 0.01 gray or 10 milligrays.
The SI definition of the second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
www.gordonengland.co.uk /conversion/sidef.htm   (7411 words)

  
 Milligram
The kilogram or kilogramme, (symbol: kg) is the SI base unit of mass.
Since 1889, the SI system defines the unit to be equal to the mass of the international prototype of the kilogram, which is made from an alloy of platinum and iridium of 39 mm height and diameter, and is kept at the Bureau International des Poids et Mesures (International Bureau of Weights and Measures).
The gram was the base unit of the older CGS system of measurement, a system which is no longer widely used.
www.cooldictionary.com /words/Milligram.wikipedia   (1234 words)

  
 Essentials of the SI: Base & derived units
The SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1.
Examples of such SI derived units are given in Table 2, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted.
For a graphical illustration of how the 22 derived units with special names and symbols given in Table 3 are related to the seven SI base units, see relationships among SI units.
physics.nist.gov /cuu/Units/units.html   (468 words)

  
 Public Domain Content: SI base unit   (Site not responding. Last check: 2007-10-06)
Electric current (I) Unit: ampere (A) The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per metre of length.
Thermodynamic temperature (T) Unit: Kelvin (K) The Kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
Luminous Intensity (I) Unit: candela (cd) The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
www.publicdock.com /Physics/SI_base_unit.shtml   (338 words)

  
 Talk:SI base unit - Wikipedia, the free encyclopedia
I don't really understand why it needs to be a base unit at all; it seems lie a better base unit would be 1.
Ampere, a base unit, is defined in terms of a Newton, which is not a base unit?
I am not a physicist, but I don't really see any problem with defining base units in terms of non-base units — as long as there are no circular references — since those non-base units are in turn defined in terms of base units.
wikipedia.com /wiki/Talk:SI_base_unit   (586 words)

  
 base SI unit concept from the Astronomy knowledge base   (Site not responding. Last check: 2007-10-06)
Kelvin (12 facts) (K, absolute) - The fraction 1/273.16 of the thermodynamic temperature of the triple point of water (the point at which the solid, liquid and gaseous phase of pure water are in equilibrium).
Kilogram is equal to the mass of 1.000028 cubic decimeters of water at the temperature of its maximum density., Unit of mass equal to the international prototype of the kilogram
mole (8 facts) (mol) - The SI unit of the amount of substance, defined as the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon 12.
www.csi.uottawa.ca:4321 /astronomy/baseSIunit.html   (480 words)

  
 SI base unit: Definition and Links by Encyclopedian.com - All about SI base unit   (Site not responding. Last check: 2007-10-06)
One metre is defined as the distance light travels in a vacuum in 1/299792458 second.
The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol." 2.
www.encyclopedian.com /si/SI-base-unit.html   (326 words)

  
 SI Units   (Site not responding. Last check: 2007-10-06)
In SI, a larger or smaller unit for a physical quantity is indicated by an SI prefix, which is a prefix used in the International System to indicate a power of ten.
The kilogram (kg) is the SI base unit of mass.
The SI base unit of temperature is the kelvin (K).
chemistry.twu.edu /tutorial/SIUnits.html   (453 words)

  
 The International System of Units, by Robert A. Nelson
The unit of volume, the pinte (later renamed the litre), was defined as the volume of a cube having a side equal to one-tenth of a meter.
The unit of mass, the grave (later renamed the kilogramme), was defined as the mass of one pinte of distilled water at the temperature of melting ice.
For example, the unit of force is the newton, which is equal to a kilogram meter per second squared, and the unit of energy is the joule, equal to a newton meter.
www.aticourses.com /international_system_units.htm   (6282 words)

  
 [No title]
Subject: Re: SI Units Project: Requirements Hi Mark (and all) I'm very glad to get his email as I was starting to worry that the project has gone by the wayside.
SI uses the > > following > > fundamental units, and a coulomb is derived as ampere seconds (amperes > > used > > to be derived as coulombs per second in the earlier cgs system).
SI uses the > following > fundamental units, and a coulomb is derived as ampere seconds (amperes > used > to be derived as coulombs per second in the earlier cgs system).
homepage.ntlworld.com /mark.easterbrook/mentored/digest005.txt   (2500 words)

  
 Units: SI Fundamental Units
The General Conference on Weights and Measures has replaced all but one of the definitions of its base (fundamental) units based on physical objects (such as standard meter sticks or standard kilogram bars) with physical descriptions of the units based on stable properties of the Universe.
For example, the second, the base unit of time, is now defined as that period of time in which the waves of radiation emitted by cesium atoms, under specified conditions, display exactly 9 192 631 770 cycles.
The meter, the base unit of distance, is defined by stating that the speed of light, a universal physical constant, is exactly 299 792 458 meters per second.
www.unc.edu /~rowlett/units/sifundam.html   (612 words)

  
 base SI unit Comparison Table   (Site not responding. Last check: 2007-10-06)
in 1933 it was based on the luminous emission of a flbody at the freezing temperature of platinum (2045 K) cd
Unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water
Unit of mass equal to the international prototype of the kilogram
www.csi.uottawa.ca:4321 /astronomy/baseSIunit_table.html   (323 words)

  
 SI (en)
SI base unit Symbol Name Base quantity m metre; US: meter length kg kilogram mass s second time A ampere electrical current K kelvin thermodynamic temperature mol mole amount of substance cd candela luminous intensity The mass is commonly called the weight in people's daily life and trade.
The International System of Units (SI) is the modern metric system and adopted by the International Organization for Standardization (ISO) as International Standard ISO 1000.
The United States signed the Convention of the Metre (Meter Convention in American English) in 1875, but limited use of the SI and overuse of the inch-pound units cause obstacles.
www.geocities.com /jusjih/si-en.html   (792 words)

  
 Metric System Units
SI was established in 1960, at the 11th General Conference on Weights and Measures.
There are three major parts to the metric system: the seven base units, the prefixes and units built up from the base units.
The amount of a substance of specified chemical formula, containing the same number of formula units (molecules, atoms, ions, electrons, etc.) as there are in 0.012 kilograms (exactly) of the pure nuclide carbon-12.
dbhs.wvusd.k12.ca.us /webdocs/Metric/Metric-Units.html   (1269 words)

  
 BIPM - SI
The base units are a choice of seven well-defined units which by convention are regarded as dimensionally independent: the metre, the kilogram, the second, the ampere, the kelvin, the mole, and the candela.
Derived units are those formed by combining base units according to the algebraic relations linking the corresponding quantities.
The names and symbols of some of the units thus formed can be replaced by special names and symbols which can themselves be used to form expressions and symbols of other derived units.
www.bipm.fr /en/si   (178 words)

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