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SI base units
The SI is established on 7 SI base units for 7 base quantities assumed come be support independent, as provided in Table 1.

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Table 1. SI basic units Base amount Name prize
SI basic unit
length meter m
mass kilogram kg
time second s
electric current ampere A
thermodynamic temperature kelvin K
amount of substance mole mol
luminous intensity candela cd

For thorough information ~ above the SI basic units, see definitions of the SI basic units and their historic context. SI acquired units various other quantities, called obtained quantities, are defined in regards to the seven base amounts via a device of amount equations. The SI derived units because that these obtained quantities are acquired from this equations and also the seven SI basic units. Instances of such SI acquired units are provided in Table 2, wherein it have to be provided that the price 1 for quantities of dimension 1 such as mass portion is typically omitted. acquired quantity name Symbol
Table 2. Examples of SI acquired units
SI derived unit
area square meter m2
volume cubic meter m3
speed, velocity meter every second m/s
acceleration meter per second squared m/s2
wave number reciprocal meter m-1
mass density kilogram per cubic meter kg/m3
specific volume cubic meter every kilogram m3/kg
current density ampere per square meter A/m2
magnetic field strength ampere every meter A/m
amount-of-substance concentration mole per cubic meter mol/m3
luminance candela per square meter cd/m2
mass fraction kilogram every kilogram, which might be stood for by the number 1 kg/kg = 1
obtained quantity surname Symbol Expressionin terms ofother SI systems Expressionin state ofSI base devices
For ease of understanding and also convenience, 22 SI obtained units have actually been given special names and symbols, as displayed in Table3. Table 3. SI acquired units through special names and symbols
SI obtained unit
plane angle radian (a) rad - m·m-1 = 1 (b)
solid angle steradian (a) sr (c) - m2·m-2 = 1 (b)
frequency hertz Hz - s-1
force newton N - m·kg·s-2
pressure, stress pascal Pa N/m2 m-1·kg·s-2
energy, work, quantity of heat joule J N·m m2·kg·s-2
power, radiant flux watt W J/s m2·kg·s-3
electric charge, quantity of electricity coulomb C - s·A
electric potential difference, electromotive force volt V W/A m2·kg·s-3·A-1
capacitance farad F C/V m-2·kg-1·s4·A2
electric resistance ohm Omega V/A m2·kg·s-3·A-2
electric conductance siemens S A/V m-2·kg-1·s3·A2
magnetic flux weber Wb V·s m2·kg·s-2·A-1
magnetic flux density tesla T Wb/m2 kg·s-2·A-1
inductance henry H Wb/A m2·kg·s-2·A-2
Celsius temperature degree Celsius °C - K
luminous flux lumen lm cd·sr (c) m2·m-2·cd = cd
illuminance lux lx lm/m2 m2·m-4·cd = m-2·cd
activity (of a radionuclide) becquerel Bq - s-1
absorbed dose, particular energy (imparted), kerma gray Gy J/kg m2·s-2
dose tantamount (d) sievert Sv J/kg m2·s-2
catalytic activity katal kat s-1·mol
(a) The radian and steradian may be used advantageously in expressions for acquired units come distinguish between quantities of a various nature yet of the same dimension; some instances are offered in Table 4. (b) In practice, the icons rad and also sr are supplied where appropriate, however the acquired unit "1" is generally omitted. (c) In photometry, the unit surname steradian and the unit price sr space usually preserved in expression for obtained units. (d) various other quantities to express in sieverts space ambient sheep equivalent, directional sheep equivalent, an individual dose equivalent, and organ indistinguishable dose.
note on degree Celsius. The derived unit in Table 3 through the unique name degree Celsius and special prize °C deserves comment. Because of the way temperature scales used to it is in defined, it remains usual practice to express a thermodynamic temperature, prize T, in terms of its difference from the reference temperature T0 = 273.15 K, the ice cream point. This temperature distinction is called a Celsius temperature, symbol t, and also is defined by the quantity equation

t= T- T0.

The unit that Celsius temperature is the level Celsius, symbol °C. The numerical value of a Celsius temperature t expressed in levels Celsius is given by

t/°C = T/K - 273.15.

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It follows from the definition of t that the degree Celsius is same in magnitude to the kelvin, which subsequently implies the the numerical value of a offered temperature difference or temperature term whose value is express in the unit level Celsius (°C) is same to the numerical value of the same distinction or interval as soon as its worth is expressed in the unit kelvin (K). Thus, temperature distinctions or temperature intervals may be to express in either the degree Celsius or the kelvin making use of the same numerical value. For example, the Celsius temperature distinction Deltat and the thermodynamic temperature distinction DeltaT between the melting point of gallium and also the triple suggest of water might be written as Deltat = 29.7546 °C = DeltaT = 29.7546 K.

The special names and symbols the the 22 SI obtained units v special names and also symbols offered in Table 3 may themselves be consisted of in the names and symbols of various other SI derived units, as shown in Table 4. derived quantity name Symbol
Table 4. Instances of SI acquired units whose names and also symbols encompass SI obtained units with special names and also symbols
SI derived unit
dynamic viscosity pascal second Pa·s
moment that force newton meter N·m
surface tension newton every meter N/m
angular velocity radian every second rad/s
angular acceleration radian per 2nd squared rad/s2
heat flux density, irradiance watt per square meter W/m2
heat capacity, entropy joule per kelvin J/K
specific warm capacity, particular entropy joule per kilogram kelvin J/(kg·K)
specific energy joule every kilogram J/kg
thermal conductivity watt per meter kelvin W/(m·K)
energy density joule every cubic meter J/m3
electric ar strength volt every meter V/m
electric charge density coulomb per cubic meter C/m3
electric flux density coulomb every square meter C/m2
permittivity farad every meter F/m
permeability henry per meter H/m
molar energy joule per mole J/mol
molar entropy, molar heat capacity joule every mole kelvin J/(mol·K)
exposure (x and also gamma rays) coulomb every kilogram C/kg
absorbed dose rate gray per second Gy/s
radiant intensity watt per steradian W/sr
radiance watt every square meter steradian W/(m2·sr)
catalytic (activity) concentration katal every cubic meter kat/m3