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Description
The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency βΞ½Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to sβ1.
Abbreviation: s
Reference: Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216 ISBN 978-92-822-2272-0. - Β»Open Access pdfΒ«
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- Entity, count, and number, and SI base quantities / SI base units
Quantity name Symbol Unit name Symbol Comment elementary UX elementary unit [x] UX, UB; [x] not in SI count NX elementary unit [x] NX, NB; [x] not in SI number N - dimensionless = NXΒ·UX-1 amount of substance nB mole [mol] nX, nB electric current I ampere [A] A = CΒ·s-1 time t second [s] length l meter [m] SI: metre mass m kilogram [kg] thermodynamic temperature T kelvin [K] luminous intensity IV candela [cd]
- Fundamental relationships
- Β» Avogadro constant NA
- Β» Boltzmann constant k
- Β» elementary charge e
- Β» Faraday constant F
- Β» gas constant R
- Β» electrochemical constant f
- Fundamental relationships
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