Prab: CSV import

2024-04-16T20:52:48Z

CSV import

New page

[[File:SI_base_units.svg|SI base units|thumb]] [[File:Unit_relations_in_the_old_SI.svg|Unit relations in the old SI|thumb|left]] [[File:Unit_relations_in_the_new_SI.svg|Unit relations in the new SI|thumb|left]] '''SI base units''' are the fundamental units of measurement defined by the [[International System of Units]] (SI) for the seven basic quantities of a physical nature. These units are the building blocks of the SI system and all other units of measurement are derived from them. The SI base units and their corresponding physical quantities are: the [[meter]] (m) for length, the [[kilogram]] (kg) for mass, the [[second]] (s) for time, the [[ampere]] (A) for electric current, the [[kelvin]] (K) for thermodynamic temperature, the [[mole]] (mol) for the amount of substance, and the [[candela]] (cd) for luminous intensity.

==Definition of SI Base Units==
Each of the SI base units is defined by a specific physical phenomenon or a fundamental physical property, ensuring that they are universally accessible and can be consistently reproduced in laboratories around the world.

* The '''meter''' is defined by the distance light travels in vacuum in 1/299,792,458 of a second.
* The '''kilogram''' is defined by the Planck constant, h, which is exactly 6.62607015×10^−34 kg⋅m^2⋅s^−1.
* The '''second''' is defined by the transition frequency of cesium-133 atoms, Δν_Cs.
* The '''ampere''' is defined by the elementary charge, e, which is 1.602176634×10^−19 coulombs.
* The '''kelvin''' is defined by the Boltzmann constant, k, which is 1.380649×10^−23 J⋅K^−1.
* The '''mole''' is defined by the Avogadro constant, N_A, which is 6.02214076×10^23 entities per mole.
* The '''candela''' is defined by the luminous efficacy of monochromatic radiation of frequency 540×10^12 Hz, K_cd, which is 683 lm/W.

==Importance of SI Base Units==
The SI base units play a crucial role in science, technology, and commerce by providing a universal language for measurement. This standardization allows for the precise and accurate exchange of information globally, facilitating international collaboration and innovation. The definitions of these units are periodically reviewed and updated by the [[International Committee for Weights and Measures]] (CIPM) to incorporate advancements in measurement science and technology.

==Recent Changes to SI Base Units==
In 2019, a significant revision of the SI base units took place, where all units were redefined in terms of physical constants. This shift from artifact-based definitions (e.g., the kilogram being defined by a physical object) to constant-based definitions ensures greater stability and universality of the measurement system.

==See Also==
* [[International System of Units]]
* [[Physical quantity]]
* [[Unit of measurement]]
* [[Metric system]]

[[Category:Units of measurement]]
[[Category:SI units]]

{{stb}}

SI base unit - Revision history

Prab: CSV import