01 Jan 2018

SI Units

The SI system ( Systeme International d'Unite) consists of 7 basic units.

This rationalised system of units was adopted internationally in 1960.

From these basic units useful derived units have been defined.

Unit	SI name	SI symbol	Relationship	SI basic units
frequency	hertz	Hz		s^-1
speed, velocity				m / s
plane angle	radian	rad		m x m^-1 = 1
angular velocity			rad / s	s^-1
acceleration				m / s²
angular acceleration			rad / s²	s^-2
area				m²
volume				m³
mass density				kg / m³
specific volume				m³ / kg
force	newton	N		kg x m x s^-2
work, energy, heat	joule	J	N x m	m²x kg x s^-2
pressure, stress	pascal	Pa	N / m²	m^-1x kg x s^-2
power	watt	W	J / s	m² x kg x s^-3
electric potential difference, EMF	volt	V	W / A	m² x kg x s^-3 x A^-1
electric resistance	ohm	Ω	V / A	m² x kg x s^-3 x A^-2
electric conductance	siemens	S	A / V	m^-2 x kg^-1 x s³ x A²
current density				A / m²
electric charge	coulomb	C		s x A
capacitance	farad	F	C / V	m^-2 x kg^-1 x s⁴ x A²
magnetic flux	weber	Wb	V x s	m² x kg x s^-2 x A^-1
magnetic flux density	tesla	T	Wb / m²	kg x s^-2 x A^-1
magnetic field strength				A / m
inductance	henry	H	Wb/ A	m² x kg x s^-2 x A^-2
Celsius temperature	degree Celsius	°C		K

Prefixes can be added to indicate multiples of the basic SI unit.