SI units and derivations

The seven SI base units are given in the table below. These units are assumed to be independent of each other.

base quantity SI base unit symbol
length, position meter $ \mathrm{m}$
mass kilogram $ \mathrm{kg}$
time second $ \mathrm{s}$
current ampere $ \mathrm{A}$
temperature Kelvin $ \mathrm{K}$
amount of substance mole $ \mathrm{mol}$
intensity candela $ \mathrm{cd}$

There are many quantities that can be measured using units that are derived from the base units. Some of these are written in terms of the base units. Some examples are given in the table below.

quantity SI derived unit symbol
area square meter $ \mathrm{m^2}$
volume cubic meter $ \mathrm{m^3}$
speed, velocity meter per second $ \mathrm{m/s}$
acceleration meter per second squared $ \mathrm{m/s^2}$
density kilogram per cubic meter $ \mathrm{kg/m^3}$
specific volume cubic meter per kilogram $ \mathrm{m^3/kg}$
concentration mole per cubic meter $ \mathrm{mol/m^3}$
wave number reciprocal meter $ \mathrm{m^{-1}}$
current density ampere per square meter $ \mathrm{A/m^2}$
magnetic field strength ampere per cubic meter $ \mathrm{A/m^3}$
luminance candela per square meter $ \mathrm{cd/m^2}$

Other derived units have their own names. Some examples are given in the table below.

quantity SI unit symbol derivation from other SI units
volume liter $ \mathrm{L}$ or $ \mathrm{\ell}$ $ \mathrm{10^{-3}m^3}$
plane angle radian $ \mathrm{rad}$  
solid angle steradian $ \mathrm{sr}$  
frequency hertz $ \mathrm{Hz}$ $ \mathrm{s^{-1}}$
force newton $ \mathrm{N}$ $ \mathrm{kg \cdot m/s^2}$
pressure, stress Pascal $ \mathrm{Pa}$ $ \mathrm{N/m^2}$
energy, work joule $ \mathrm{J}$ $ \mathrm{N \cdot m}$
power watt $ \mathrm{W}$ $ \mathrm{J/s}$
charge coulomb $ \mathrm{C}$ $ \mathrm{A \cdot s}$
potential difference volt $ \mathrm{V}$ $ \mathrm{W/A}$
resistance ohm $ \mathrm{\Omega}$ $ \mathrm{V/A}$
temperature degree Celsius $ \mathrm{{}^{\circ}C}$ $ \mathrm{K}+273.15$






Reference: National Institute of Standards and Technology, http://physics.nist.gov/cuu/Units/



Contributors to this entry (in most recent order):

As of this snapshot date, this entry was owned by Wkbj79.