General Conference on Weights and Measures

The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM). It is one of the three organizations established to maintain the International System of Units (SI) under the terms of the Convention du Mètre (Metre Convention) of 1875. It meets in Paris every four to six years. In 2002 the CGPM represented 51 member states and ten further associ ...

Including:

• General Conference on Weights and Measures - CGPM Meetings

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The degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. The Celsius scale sets 0.01 °C to be at the triple point of water and a degree Celsius to be 1/273.16 of the difference in temperature between the triple point of water and absolute zero. Until 1954 the scale was defined with the freezing point of water at 0 °C and the boiling point at 100 °C at standard atmospheric pressure, this definition is still a close approximation to ...

Including:

• Celsius - History
• Celsius - Naming
• Celsius - Application
• Celsius - Comparison of temperature scales

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The volt (symbol: V) is the SI derived unit of electric potential difference. The number of volts is a measure of the strength of an electrical source in the sense of how much power is produced for a given current level. It is named in honor of Alessandro Volta (1745–1827), who invented the voltaic pile, the first chemical battery. Volt - Definition. The volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. Hence, it is the base SI repres ...

Including:

• Volt - Definition
• Volt - Explanation
• Volt - Electrical potential difference voltage
• Volt - Hydraulic analogy
• Volt - Technical definition
• Volt - Useful formulae
• Volt - DC circuits
• Volt - AC circuits
• Volt - AC conversions
• Volt - Total voltage
• Volt - Voltage drops
• Volt - Examples
• Volt - Voltage sources
• Volt - Common voltages
• Volt - Measuring instruments
• Volt - History of the volt

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The second (symbol: s) is the SI base unit of time. It is often abbreviated sec. in non-SI usage. Second - Definition. 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 caesium-133 atom. Leap second, Orders of magnitude (time), UTC, Atomic clock Second - Origin. Originally, the second was known as a "second minute", ...

Including:

• Second - Definition
• Second - Origin
• Second - Conversions
• Second - Explanation

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The International Bureau of Weights and Measures is the English name of the Bureau international des poids et mesures (BIPM, often written in English Bureau International des Poids et Mesures), a standards organization, one of the three organizations established to maintain the International System of Units (SI) under the terms of the Convention du Mètre (Metre Convention). Note that the abbreviation IBWM does not exist. It is based at th ...

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The metric system was officially adopted in France after the French Revolution. During the history of the metric system a number of variations have evolved and their use spread around the world replacing many traditional measurement systems. By the end of World War II a number of different systems of measurement were still in use throughout the world. Some of these systems were metric system variations whilst others were based on the Imperial and American systems. It was recognised that additional steps were needed to promote a worldw ...

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SI, SI - History, SI - Units, SI - SI writing style, SI - Spelling variations, SI - Cultural issues

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The factor of 60 comes from the Babylonians who used factors of 60 in their counting system. The hour had previously been defined by the ancient Egyptians in terms of the rotation of the Earth as 1/24 of a solar day. This made the second 1/86,400 of a solar day. With the development of clocks keeping mean time (as opposed to the apparent time displayed by sundials), the second became 1/86,400 of a mean solar day. In 1956 the second was defined in terms of the period of revolution of the Earth around the Sun for a particu ...

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Second, Second - Definition, Second - Origin, Second - Conversions, Second - Explanation

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The Celsius temperature scale was originally designed so that the freezing point of water is 100 degrees, and its boiling point is 0 degrees at standard atmospheric pressure. This was reversed to its modern order some time after his death, in part at the instigation of Daniel Ekström, the manufacturer of most of the thermometers used by Celsius. Several other people, including Per Elvius the Elder from Sweden (1710) and Christian of Lyons (1743), independently invented the same temperature scale. The oft-quoted claim that the botanist Carolus Linnaeus (1740) is amongst those is unsubstantiated. The Delisle scale was another tem ...

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Celsius, Celsius - History, Celsius - Naming, Celsius - Application, Celsius - Comparison of temperature scales

Read more here: » Celsius: Encyclopedia II - Celsius - History

The metric system was created during the French Revolution. On August 1, 1793 the National Convention adopted the new decimal "metre" with a provisional length as well as the other decimal units with preliminary definitions and terms. On April 7, 1795 (Loi du 18 germinal, an III) the terms gramme and kilogramme repaced the former terms "gravet" and "grave". After the 18 Brumaire Year VIII, the metric system was definitively adopted in France by the First Consul Bonaparte, (the later Napoleon I) on Decembre 10, 1799 (Loi ...

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SI, SI - History, SI - Units, SI - SI writing style, SI - Spelling variations, SI - Cultural issues, SI - Trade

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By definition from Ohm's Law, a device has a resistance of one ohm if a voltage of one volt causes a current of one ampere to flow (R = V/I). Alternatively and equivalently, a device that dissipates one watt of power with one ampere of current flowing through it has a resistance of one ohm (R = P / I 2). Since 1990, the ohm has been maintained internationally using the quantum Hall effect, where a conventional value is used for the 'von-Klitzing constant', fixed by the 18th General Conference on Weights and Measures as < ...

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Ohm unit, Ohm unit - Definition, Ohm unit - Origin, Ohm unit - Explanation, Ohm unit - Conversions

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There are three main exceptions to the metrication trend: the UK, the USA, and global air and sea transport industry. Contrary to popular belief, the USA and the UK do not use a common system (see English unit, Imperial unit and U.S. customary units for details). With the exception of the length, with the yard standardised at exactly 0.9144 m by an international conference in 1958, most other units differ in value in the USA and UK. A gallon of liquid, for example, is 3.8 l in the USA but 4.5 l in the UK. The USA also have ...

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Metrication, Metrication - Before the metric system, Metrication - Système International SI, Metrication - Conversion process, Metrication - Adoption, Metrication - Exceptions, Metrication - United Kingdom, Metrication - United States, Metrication - Liberia and Myanmar, Metrication - Air and sea transport, Metrication - Accidents and incidents, Metrication - Opposition

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When the metric system was introduced in France in 1795, it included units for length, area, dry volume, liquid capacity, weight or mass, and even currency, but not for time. Decimal time of day had been introduced in France two years earlier, but was set aside at the same time the metric system was inaugurated, and did not follow the metric pattern of a base unit and prefixed units. James Clerk Maxwell and Elihu Thomson (through the British Association for the Advancement of Science - BAAS) introduced the Centimetre gram second system of units (cgs) in 1874, in order to derive electric and magnetic metric units, following the recommen ...

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Metric time, Metric time - History, Metric time - Alternative Units, Metric time - Alternative Meaning

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There are three main exceptions to the metrication trend: the UK, the U.S., and global air and sea transport industry. Contrary to popular belief, the U.S. and the UK do not use a common system (see English unit, Imperial unit and U.S. customary units for details). With the exception of the length, with the yard standardised at exactly 0.9144 m by an international conference in 1958, most other units differ in value in the U.S. and UK. A gallon of liquid, for example, is 3.8 l in the U.S. but 4.5 l in the UK. The U.S. also has ...

See also:

Metrication, Metrication - Before the metric system, Metrication - Système International SI, Metrication - Conversion process, Metrication - Adoption, Metrication - Exceptions, Metrication - United Kingdom, Metrication - United States, Metrication - Liberia and Myanmar, Metrication - Air and sea transport, Metrication - Accidents and incidents, Metrication - Opposition

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The Centigrade scale is the original scale devised by Anders Celsius (1701-1744) in which the boiling point of water at 1,000 millibars was defined as 0 degrees and the freezing point of water was defined as 100 degrees. This is exactly the reverse of the modern Celsius scale, named after Anders Celsius. It was then reversed to its modern order some time after his death, in part at the instigation of Daniel Ekström, the manufacturer of most of the thermometers used by Celsius. Several other people, including Per Elvius the Elder from Sweden ...

See also:

Celsius, Celsius - History, Celsius - Naming, Celsius - Application, Celsius - Comparison of temperature scales

Read more here: » Celsius: Encyclopedia II - Celsius - History

The electrical potential difference can be thought of as the ability to move electrical charge through a resistance. In essence, the volt measures how much kinetic energy each electron carries. The number of electrons is measured by the charge, in coulombs. Thus the volt is multiplied by the current flow, in amperes which are one coulomb per second, to yield the total electrical power in the current, in Watts. At a time in physics when the word force was used loosely, the potential difference was named the electromotive force or emf - a term which is still used in certain contexts. Volt - Electrical ...

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Volt, Volt - Definition, Volt - Explanation, Volt - Electrical potential difference voltage, Volt - Hydraulic analogy, Volt - Technical definition, Volt - Useful formulae, Volt - DC circuits, Volt - AC circuits, Volt - AC conversions, Volt - Total voltage, Volt - Voltage drops, Volt - Examples, Volt - Voltage sources, Volt - Common voltages, Volt - Measuring instruments, Volt - History of the volt

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This refers to those territories where a country is sovereign, but which cannot be reached without entering another country. The best-known example was West Berlin, before the reunification of Germany, which was de facto a West German exclave within East Germany, and thus an East German enclave (many small West Berlin land areas, such as Steinstücken, were in turn separated from the main one, some by only a few meters). De jure all of Berlin was ruled by the four Allied powers; this meant that West Berlin could not send voting members to the German Parliament, and that it ...

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Enclave, Enclave - Enclaved countries, Enclave - Coastal countries, Enclave - Coastal fragments, Enclave - True enclaves, Enclave - Practical enclaves, Enclave - Subnational enclaves, Enclave - Ethnic enclaves, Enclave - Extraterritoriality, Enclave - Land ceded to a Foreign Country

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The international system of units consists of a set of units together with a set of prefixes. The units of SI can be divided into two subsets. There are the seven base units. Each of these base units are dimensionally independent. From these seven base units several other units are derived. In addition to the SI units there are also a set of non-SI units accepted for use with SI. A prefix may be added to units to produce a multiple of the original unit. All multiples are integer powers of ten. For example, kilo- denotes a multi ...

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SI, SI - History, SI - Units, SI - SI writing style, SI - Spelling variations, SI - Cultural issues, SI - Trade

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SI - Spelling variations. Several nations, notably the United States, typically use the spellings 'meter' and 'liter' instead of 'metre' and 'litre' in keeping with standard American English spelling. In addition, the official US spelling for the SI prefix 'deca' is 'deka'. The unit 'gram' is also sometimes spelled 'gramme' in English-speaking countries other than the United States, though that is an older spelling and its use is declining. ...

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SI, SI - History, SI - Units, SI - SI writing style, SI - Spelling variations, SI - Cultural issues, SI - Trade

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Medieval trade was organized on a city-by-city basis by guilds, which set local laws on weights and measures. For example, the ell or elle was a unit of length commonly used in Europe, but its value varied from 40.2 cm in one part of Germany to 70 cm in The Netherlands to 94.5 cm in Edinburgh. A survey of Switzerland in 1838 revealed that the foot had 37 different regional variations, the ell had 68, there were 83 different measures for dry grain and 70 for fluids, and 63 different measures for "dea ...

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Metrication, Metrication - Before the metric system, Metrication - Système International SI, Metrication - Conversion process, Metrication - Adoption, Metrication - Exceptions, Metrication - United Kingdom, Metrication - United States, Metrication - Liberia and Myanmar, Metrication - Air and sea transport, Metrication - Accidents and incidents, Metrication - Opposition

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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. International factors also affected the adoption of the metric system, as many countries increased their trade. Scientifically, it provides ease when dealing with very large and small quantities because it lines up so ...

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SI, SI - History, SI - Units, SI - SI writing style, SI - Spelling variations, SI - Cultural issues

Read more here: » SI: Encyclopedia II - SI - Cultural issues