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The henry (symbol: H) is the unit of electrical inductance in the International System of Units (SI). [1] If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self-inductance of 1 henry. The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same ...
4.6 Chemistry. 5 Weight. ... used from 1495 to 1587, as affirmed by King Henry VII, ... Metrication – Conversion to the metric system of measurement;
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
The first group of metric units are those that are at present defined as units within the International System of Units (SI). In its most restrictive interpretation, this is what may be meant when the term metric unit is used. The unit one (1) is the unit of a quantity of dimension one. It is the neutral element of any system of units. [2]
The International System of Units, or SI, [1]: 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 ...
Multiples and submultiples of metric units are related by powers of ten and their names are formed with prefixes. This relationship is compatible with the decimal system of numbers and it contributes greatly to the convenience of metric units. In the early metric system there were two base units, the metre for length and the gram for mass. The ...
The Green Book is a direct successor of the Manual of Symbols and Terminology for Physicochemical Quantities and Units, originally prepared for publication on behalf of IUPAC's Physical Chemistry Division by M. L. McGlashen in 1969. A full history of the Green Book's various editions is provided in the historical introduction to the third edition.
The International System of Units is the modern metric system. It is based on the metre–kilogram–second–ampere (MKSA) system of units from early in the 20th century. [20] It also includes numerous coherent derived units for common quantities like power (watt) and irradience (lumen).