SI units

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SI units (Système International d'Unites) Internationally agreed system of units, derived from the mks (metre, kilogram, and second) system. SI units are now used for many scientific purposes, and have replaced the fps (foot, pound, and second) and cgs (centimetre, gram, and second) systems. The seven basic units are: the metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electrical current, Kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.

Measurement

Unit

Symbol

Basic units

Length

metre

m

Mass

kilogram

kg

Time

second

s

Electric current

ampere

A

Thermodynamic temperature

kelvin

K

Amount of substance

mole

mol

Luminous intensity

candela

cd

Supplementary units

Plane angle

radian

rad

Solid angle

steradian

sr

Derived units

Frequency

hertz

Hz

Force

newton

N

Pressure, stress

pascal

Pa

Work (energy, heat)

joule

J

Power

watt

W

Electric charge

coulomb

C

Electromotive force

volt

V

Electric resistance

ohm

1/2

Electric conductance

siemens

S

Electric capacitance

farad

F

Inductance

henry

H

Magnetic flux

weber

Wb

Magnetic flux density

tesla

T

Illuminance

lux

lx

Luminous flux

lumen

lm

Radiation exposure

röntgen

r

Radiation activity

becquerel

Bq

Radiation absorbed dose

gray

Gy

Radiation dose equivalent

sievert

Sv

Celsius temperature

°Celsius

°C


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