SI
The International System of Units (abbreviated as SI, from the French "Système international d'unités") is the modern form of the metric system and the most widely used system of measurement worldwide. It is the standard system of measurement in science, industry, and commerce.
History[edit | edit source]
The SI was established in 1960 by the General Conference on Weights and Measures (CGPM) and is maintained by the International Bureau of Weights and Measures (BIPM). It was developed to provide a coherent and universal system of measurement based on the metric system, which originated in France in the late 18th century.
Structure[edit | edit source]
The SI is built upon seven base units, from which all other units of measurement are derived. These base units are:
- Metre (m) - the unit of length
- Kilogram (kg) - the unit of mass
- Second (s) - the unit of time
- Ampere (A) - the unit of electric current
- Kelvin (K) - the unit of thermodynamic temperature
- Mole (mol) - the unit of amount of substance
- Candela (cd) - the unit of luminous intensity
Derived Units[edit | edit source]
Derived units are formed by combining the base units according to the algebraic relationships linking the corresponding quantities. Some common derived units include:
- Newton (N) - the unit of force
- Joule (J) - the unit of energy
- Watt (W) - the unit of power
- Pascal (Pa) - the unit of pressure
Prefixes[edit | edit source]
The SI uses a set of prefixes to denote multiples and submultiples of units. These prefixes are based on powers of ten and include:
- Kilo (k) - 10^3
- Mega (M) - 10^6
- Giga (G) - 10^9
- Milli (m) - 10^-3
- Micro (µ) - 10^-6
- Nano (n) - 10^-9
Importance[edit | edit source]
The SI is crucial for ensuring consistency and accuracy in scientific research, engineering, and commerce. It facilitates international collaboration and trade by providing a common language of measurement.
Recent Developments[edit | edit source]
In 2019, the SI underwent a significant revision, where four of the base units (kilogram, ampere, kelvin, and mole) were redefined in terms of fundamental physical constants, such as the Planck constant and the Avogadro constant. This change was made to improve the precision and stability of these units.
Also see[edit | edit source]
- Metric system
- Imperial units
- Measurement
- General Conference on Weights and Measures
- International Bureau of Weights and Measures
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