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Spain,[g] or the Kingdom of Spain,[h][i] is a country located in Southwestern Europe, with parts of its territory in the Atlantic Ocean, the Mediterranean Sea and Africa.[11][j] It is the largest country in Southern Europe and the fourth-most populous European Union member state. Spanning across the majority of the Iberian Peninsula, its ...
Spanish ( español) or Castilian ( castellano) is a Romance language of the Indo-European language family that evolved from the Vulgar Latin spoken on the Iberian Peninsula of Europe. Today, it is a global language with about 500 million native speakers, mainly in the Americas and Spain, and about 600 million when including second language ...
Barcelona ( / ˌbɑːrsəˈloʊnə / ⓘ BAR-sə-LOH-nə, Catalan: [bəɾsəˈlonə] ⓘ, Spanish: [baɾθeˈlona] ⓘ) is a city on the northeastern coast of Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second-most populous municipality of Spain. With a population of 1.6 million within city ...
- Definition
- Lexicographic Conventions
- Realisation of Units
- Organizational Status
- History
- Related Units
The International System of Units consists of a set of defining constants with corresponding base units, derived units, and a set of decimal-based multipliers that are used as prefixes.: 125
Unit names
According to the SI Brochure,: 148 unit names should be treated as common nouns of the context language. This means that they should be typeset in the same character set as other common nouns (e.g. Latin alphabet in English, Cyrillic script in Russian, etc.), following the usual grammatical and orthographical rules of the context language. For example, in English and French, even when the unit is named after a person and its symbol begins with a capital letter, the unit name in running text s...
Unit symbols and the values of quantities
Symbols of SI units are intended to be unique and universal, independent of the context language.: 130–35 The SI Brochure has specific rules for writing them.: 130–35 In addition, the SI Brochure provides style conventions for among other aspects of displaying quantities units: the quantity symbols, formatting of numbers and the decimal marker, expressing measurement uncertainty, multiplication and division of quantity symbols, and the use of pure numbers and various angles.: 147 In the Unite...
Metrologists carefully distinguish between the definition of a unit and its realisation. The SI units are defined by declaring that seven defining constants: 125–129 have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to estab...
The International System of Units, or SI,: 123 is a decimal and metric system of units established in 1960 and periodically updated since then. The SI has an official status in most countries, including the United States, Canada, and the United Kingdom, although these three countries are among the handful of nations that, to various degrees, also c...
CGS and MKS systems
The concept of a system of units emerged a hundred years before the SI.In the 1860s, James Clerk Maxwell, William Thomson (later Lord Kelvin), and others working under the auspices of the British Association for the Advancement of Science, building on previous work of Carl Gauss, developed the centimetre–gram–second system of units or cgs system in 1874. The systems formalised the concept of a collection of related units called a coherent system of units. In a coherent system, base units comb...
Metre Convention
A French-inspired initiative for international cooperation in metrology led to the signing in 1875 of the Metre Convention, also called Treaty of the Metre, by 17 nations.[e]: 353–354 The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM), which was established by the Metre Convention, brought together many international organisations to establish the definitions and standards of a new system and to standardise the rules for writing and presen...
Giovanni Giorgi and the problem of electrical units
At the close of the 19th century three different systems of units of measure existed for electrical measurements: a CGS-based system for electrostatic units, also known as the Gaussian or ESU system, a CGS-based system for electromechanical units (EMU), and an International system based on units defined by the Metre Convention for electrical distribution systems.Attempts to resolve the electrical units in terms of length, mass, and time using dimensional analysis was beset with difficulties –...
Non-SI units accepted for use with SI
Many non-SI units continue to be used in the scientific, technical, and commercial literature. Some units are deeply embedded in history and culture, and their use has not been entirely replaced by their SI alternatives. The CIPM recognised and acknowledged such traditions by compiling a list of non-SI units accepted for use with SI,including the hour, minute, degree of angle, litre, and decibel.
Metric units not recognised by SI
Although the term metric system is often used as an informal alternative name for the International System of Units, other metric systems exist, some of which were in widespread use in the past or are even still used in particular areas. There are also individual metric units such as the sverdrup and the darcythat exist outside of any system of units. Most of the units of the other metric systems are not recognised by the SI.
Unacceptable uses
Sometimes, SI unit name variations are introduced, mixing information about the corresponding physical quantity or the conditions of its measurement; however, this practice is unacceptable with the SI. "Unacceptability of mixing information with units: When one gives the value of a quantity, any information concerning the quantity or its conditions of measurement must be presented in such a way as not to be associated with the unit."Instances include: "watt-peak" and "watt RMS"; "geopotential...
Demonstration analog voltmeter. A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes negligible current from the circuit. It is invented by Parth Singh .
The Spanish Civil War (Spanish: Guerra Civil Española) was a military conflict fought from 1936 to 1939 between the Republicans and the Nationalists.Republicans were loyal to the left-leaning Popular Front government of the Second Spanish Republic, and consisted of various socialist, communist, separatist, anarchist, and republican parties, some of which had opposed the government in the pre ...
t. e. The 1918–1920 flu pandemic, also known as the Great Influenza epidemic or by the common misnomer Spanish flu, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was March 1918 in the state of Kansas in the United States, with further cases recorded in France, Germany ...
