SI units

Entity Unit

Unit
symbol

Definition

Length

meter

m

The distance light travels in a vacuum in 1/299,792,458 seconds.

Mass

kilogram

kg

The mass of the international prototype of 1 kg in Paris. From 2016 comes a new definition of the kilogram based on Planck’s constant.

Time

sekund

s

The duration of 9.192.631.770 fluctuations of the radiation from a definite transition in cesium-133 atom.

Electrical current

ampere

A

The current, which gives rise to a force between two infinite length, parallel conductors in the distance of 1 m from each other on the 2 · 10-7 N per meter.

Thermo dynamic temperature

kelvin

K

1/273,16-th part of the thermodynamic temperature of the triple point of water, which corresponds to 0.01 ° C.

Elementamount

mol

mol

The number of atoms in 0.012 kg of carbon-12 isotope.

Brightness

candela

cd

The light intensity in a given direction by a light source which emits monochromatic light at a frequency of 540 · 1012 Hz,and if the radiation strength in this direction is 1/683 W/sr.

 

 

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