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Topic: System of units


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SI

  
  Units: The International System
For example, the SI unit of force, the newton, is defined to be the force that accelerates a mass of one kilogram at the rate of one meter per second per second.
units for measurement of magnetism: the weber (flux), tesla (flux density), and henry (inductance);
These units are supposed to be "defined in relation to the SI in every document in which they are used," and "their use is not encouraged." These barely-tolerated units might well be prohibited by future meetings of the CGPM.
www.unc.edu /~rowlett/units/sipm.html   (1012 words)

  
 Unit Systems
Unit systems are built upon the necessity to describe seven fundamental quantities.
The cgs system is a small–unit metric system.
The SI system of units is largely based on mks definitions for base units, which is probably why it is still referred to as the 'Metric System'.
people.sinclair.edu /russellmarcks/unitsystems.html   (1722 words)

  
 Metric System - MSN Encarta
The measurements of modern science required still greater precision, however, and in 1983 the meter was defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
All units of measurement in the metric system are based on decimals—that is, units that increase or decrease by multiples of ten.
To change units in the metric system, simply move the decimal point to the right or the left, depending on whether the unit of measurement is increasing or decreasing by ten or one hundred and so on.
encarta.msn.com /encyclopedia_761561345/Metric_System.html   (776 words)

  
 International System of Units - Conservapedia
International System of Units (French Système International d'Unités, Système International or SI for short) is the agreed-upon system for measurement as adopted by periodic meetings of the forty-six-member Conférence Générale des Poids et Mesures (General Conference on Weights and Measures, abbreviated CGPM).
The United States of America also uses the US customary system, which is defined in terms of metric units since the Convention on the Meter.
It is the measure of a central angle (one having its origin as the center of a circle) that subtends an arc of the circle having a length equal to that of the radius.
www.conservapedia.com /International_System_of_Units   (3237 words)

  
 Metric System
The International System of Units, abbreviated SI (for the French name Système International d'Unités), is the most widely used system of units.
The metric system can legally be used in every country in the world (including the United States), and in many countries its use is obligatory.
The International System of Units was adopted by the 11th General Conference on Weights and Measures (CGPM) in 1960 and is built on the seven SI base units, which are used to define various SI derived units.
www.metric-conversion-tables.com /metricsystem.htm   (189 words)

  
 INTERNATIONAL SYSTEM OF UNITS
The Metric Conversion Act of 1975 commits the U.S. to the increasing use of, and voluntary conversion to, the metric system of measurement, further defining metric system as the International System of Units as interpreted or modified for the U.S. by the secretary of commerce.
The international unit of light intensity, the candela, was defined as 1/60 of the light radiated from a square centimeter of a flbody, a perfect radiator that absorbs no light, held at the temperature of freezing platinum.
The steradian is defined as the solid angle that, having its vertex in the center of a sphere, cuts off an area of the surface of the sphere equal to that of a square with sides of length equal to the radius of the sphere.
www.history.com /encyclopedia.do?vendorId=FWNE.fw..in032600.a#FWNE.fw..in032600.a   (1589 words)

  
 Units in MathML
Unit symbols are written in roman (upright) type, are not altered in the plural, are not followed by a period except at the end of a sentence, and no space is left between a prefix and a unit symbol.
A system of units is a collection of units which assign specific standards of measure (units) to a set of base and derived dimensions.
If the dimension of a unit and the conversion of that unit to SI (see SI conversion factor) are known, then converting the given information to any other system of units is straight forward so long as the conversion from SI to the target unit is known.
www.w3.org /TR/2003/NOTE-mathml-units-20031110   (3544 words)

  
  International System of Units - Encyclopedia, History, Geography and Biography   (Site not responding. Last check: )
The metric system was conceived by a group of scientists (among them, Lavoisier) which had been commissioned by king Louis XVI of France to create a unified and rational system of measures.
The worldwide adoption of the metric system as a tool of economy and everyday commerce was based to some extent on the lack of customary systems in many countries to adequately describe some concepts, or as a result of an attempt to standardize the many regional variations in the customary system.
Since most non-SI units in common use, 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.
www.arikah.com /encyclopedia/SI   (2020 words)

  
 Metric system, SI - The metric system units and history
The metric system is a system of units for measurement developed in late 18th century France by the chemist Lavoisier to replace the disparate systems of measures then in use with a unified, natural and universal system.
The whole system was derived from the properties of natural objects, namely the size of the Earth and the weight of water, and simple relations in between one unit and the other.
The original base units of the metric system could be derived from the length of a meridian of the Earth and the weight of a certain volume of pure water.
www.sciencemadesimple.com /metric_system.html   (2566 words)

  
 UNITS AND MEASUREMENT
A unit is a particular physical quantity, defined and adopted by convention, with which other particular quantities of the same kind are compared to express their value.
The SI derived units for these derived quantities are obtained from these equations and the seven SI base units.
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.
www.edinformatics.com /math_science/units.htm   (208 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)

  
 What is International System of Units? - a definition from Whatis.com - see also: SI
The meter (abbreviation, m) is the SI unit of displacement or length.
The kilogram (abbreviation, kg) is the SI unit of mass.
SI derived units include the hertz, the newton, the pascal (unit of pressure or stress), the ohm, the farad, the joule, the coulomb, the tesla, the lumen, the becquerel, the
whatis.techtarget.com /definition/0,,sid9_gci523539,00.html   (580 words)

  
 The international system of units (SI) 1.1.1
As a result, the units required by the rapidly emerging science of electricity were based on the centimetre, gram and second, with which they formed a coherent system known as the CGS electromagnetic system.
A system of units is said to be coherent when derived units are formed from the base units without the insertion of factors of proportionality other than unity.
The MKSA system thus broadened is called the International System of Units, often abbreviated to SI, and is the most satisfactory system of units we have had so far, in that it caters for the commercial and industrial activities of man as well as for the needs of science.
www.kayelaby.npl.co.uk /units_and_fundamental_constants/1_1/1_1_1.html   (1322 words)

  
 centimeter-gram-second systems of units
Many cgs units, however, are still in daily use; for example, in the controversy concerning the effect of electromagnetic fields on health, the field strengths have almost always been reported in milligauss.
The cgs electric units were much too small for practical use in engineering, which lead to the creation of the International System of units (not be confused with SI!), which is not a cgs system.
During the transition from cgs to MKSA it was often necessary to convert data expressed in units in a cgs system to units in MKSA.
www.sizes.com /units/sys_cgs.htm   (357 words)

  
 YOURUNITS.com - Metric System
The metric system is a system of units for measurement developed in late 18th century France to replace the disparate systems of measures then in use with a unified, natural and universal system.
The whole system was derived from the properties of natural objects, namely the size of the Earth and the weight of water, and simple relations in between one unit and the other.
The original base units of the metric system could be derived from the length of a meridian of the Earth and the weight of a certain volume of pure water.
www.yourunits.com /systems/metric.html   (2355 words)

  
 International System of Units
A class of units in SI that are completely defined in terms of the base units, but which have been given their own names.
Giorgi originally suggested that the electric unit be a unit of resistance, but later that was replaced by a unit of current, the ampere.
The great advantage of Giorgi's proposal was that it used familiar units of mass, length, and time and, with rationalized units (and the right choice of a value for the permeability of free space), it preserved the sizes of the practical electric units, even though they were defined in absolute rather than material terms.
www.sizes.com /units/SI.htm   (907 words)

  
 [No title]
Units for measuring all other quantities are derived in the SI by multiplying and dividing these base units.
This system of units for electromagnetic theory was derived from the base units centimetre, gram and second and found some use in experimental physics.
While the physical unit gray is used to describe just the energy absorbed, the medical unit sievert is used where the absorbed energy has been multiplied with a quality factor to quantify the health risk better.
www.cl.cam.ac.uk /~mgk25/metric-system-faq.txt   (8594 words)

  
 International System of Units Summary
Simple units, such as the cubit which is the distance between a man's elbow and the tip of his middle finger, or the span, the distance from the tip of the thumb to the tip of the little finger of an outstretched hand, were used for much of recorded history.
The swift worldwide adoption of the metric system as a tool of economy and everyday commerce was based mainly on the lack of customary systems in many countries to adequately describe some concepts, or as a result of an attempt to standardize the many regional variations in the customary system.
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.
www.bookrags.com /International_System_of_Units   (2968 words)

  
 Essentials of the SI: Base & derived units
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.
In photometry, the unit name steradian and the unit symbol sr are usually retained in expressions for derived units.
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)

  
 Beyond the Kilogram: Redefining the International System of Units
The paper suggests that all four units be redefined in terms of four different fundamental constants or atomic properties to which precise values would be assigned.
The proposed SI system would enable scientists to independently determine measurement standards without the need to refer to a particular object, the kilogram artifact, which is kept at BIPM and has been made available for comparisons on only two occasions since 1889.
For example, the new SI system would provide the basis for precise electrical measurements, without the use of approximate values assigned to two fundamental constants related to resistance and voltage, as is necessary today.
www.nist.gov /public_affairs/newsfromnist_beyond_the_kilogram.htm   (1848 words)

  
 Int'l System of Units
Examples of such SI derived units are given in Table 3, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted.
The radian and steradian may be used advantageously in expressions for derived units to distinguish between quantities of a different nature but of the same dimension; some examples are given in Table 5.
For a graphical illustration of how the 22 derived units with special names and symbols given in Table 4 are related to the seven SI base units, see relationships among SI units.
www.sas.org /SIUnits.html   (425 words)

  
 International System of Units (SI) - Encyclopedia of Earth
In 1874 the BAAS introduced the CGS system, a three-dimensional coherent unit system based on the three mechanical units centimeter, gram and second, using prefixes ranging from micro to mega to express decimal submultiples and multiples.
The sizes of the coherent CGS units in the fields of electricity and magnetism, proved to be inconvenient so, in the 1880s, the BAAS and the International Electrical Congress, predecessor of the International Electrotechnical Commission (IEC), approved a mutually coherent set of practical units.
The name International System of Units (SI) was given to the system by the 11th CGPM in 1960.
www.eoearth.org /article/International_System_of_Units_(SI)   (1494 words)

  
 SI units - International System of Units
The International System of Units (abbreviated SI) is the modern form of the metric system.
It is the world's most widely used system of units, both in everyday commerce and in science.
The SI was developed in 1960 from the metre-kilogram-second (mks) system, rather than the centimetre-gram-second (cgs) system which, in turn, had many variants.
www.convertunits.com /SI-units.php   (210 words)

  
 SI System of units
International System of Units also called SI System, French Système International D'unités, international decimal system of weights and measures derived from and extending the metric system of units.
Rapid advances in science and technology in the 19th and 20th centuries fostered the development of several overlapping systems of units of measurements as scientists improvised to meet the practical needs of their disciplines.
The early international system devised to rectify this situation was called the metre-kilogram-second (MKS) system.
www.ldeo.columbia.edu /~martins/eda/SI_System_of_units.html   (188 words)

  
 The International System of Units (SI)
This system was internationally ratified by the Metre Convention on 10 May 1875, which set up the Bureau International des Poids et Mesures (BIPM).
Lastly, during the eleventh Conférence Générale des Poids et Mesures in 1960, the International System of Units (SI) was developed.
The derived units are complementary to the base units.
www.lne.fr /metrologie_francaise/version_anglaise/pages/measurement/unites.htm   (498 words)

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