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Encyclopedia > Derived SI unit

SI derived units are part of the SI system of measurement units and are derived from the seven SI base units. Look up si, Si, SI in Wiktionary, the free dictionary. ... The former Weights and Measures office in Middlesex, England. ... The SI system of units defines seven SI base units: physical units defined by an operational definition. ...

Contents

Dimensionless derived units

The following SI units are actually dimensionless ratios, formed by dividing two identical SI units. They are therefore considered by the BIPM to be derived. Formally, their SI unit is simply the number 1, but they are given these special names, for use whenever the lack of a unit might be confusing. The International Bureau of Weights and Measures is the English name of the Bureau international des poids et mesures (BIPM, often written in English Bureau International des Poids et Mesures), a standards organisation, one of the three organizations established to maintain the International System of Units (SI) under the terms...

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Dimensionless SI units
Name Symbol Quantity Definition
radian rad Angle The unit of angle is the angle subtended at the centre of a circle by an arc of the circumference equal in length to the radius of the circle. There are 2π radians in a circle.
steradian sr Solid angle The unit of solid angle is the solid angle subtended at the centre of a sphere of radius r by a portion of the surface of the sphere having an area r2. There are 4π steradians on a sphere.

Some common angles, measured in radians. ... An angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ... A solid angle is the three dimensional analog of the ordinary angle. ...

Derived units with special names

Base units can be put together to derive units of measurement for other quantities. Some have been given names.

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Named units derived from SI base units
Name Symbol Quantity Expression in terms of other units Expression in terms of SI base units
hertz Hz Frequency 1/s s−1
newton N Force, Weight m∙kg/s2 m∙kg∙s−2
joule J Energy, Work, Heat N∙m m2∙kg∙s−2
watt W Power, Radiant flux J/s m2∙kg∙s−3
pascal Pa Pressure, Stress N/m2 m−1∙kg∙s−2
lumen lm Luminous flux cd∙sr cd
lux lx Illuminance lm/m2 m−2∙cd
coulomb C Electric charge or flux s∙A s∙A
volt V Electrical potential difference, Electromotive force W/A = J/C m2∙kg∙s−3∙A−1
ohm Ω Electric resistance, Impedance, Reactance V/A m2∙kg∙s−3∙A−2
farad F Electric capacitance C/V m−2∙kg−1∙s4∙A2
weber Wb Magnetic flux J/A m2∙kg∙s−2∙A−1
tesla T Magnetic flux density, magnetic induction V∙s/m2 = Wb/m2 = N/A∙m kg∙s−2∙A−1
henry H Inductance V∙s/A = Wb/A m2∙kg∙s−2∙A−2
siemens S Electric conductance 1/Ω m−2∙kg−1∙s3∙A2
becquerel Bq Radioactivity (decays per unit time) 1/s s−1
gray Gy Absorbed dose (of ionizing radiation) J/kg m2∙s−2
sievert Sv Equivalent dose (of ionizing radiation) J/kg m2∙s−2
katal kat Catalytic activity mol/s s−1∙mol
degree Celsius °C Thermodynamic temperature T°C = TK − 273.16

Look up si, Si, SI in Wiktionary, the free dictionary. ... A physical quantity is either a quantity within physics that can be measured (e. ... The SI system of units defines seven SI base units: physical units defined by an operational definition. ... The hertz (symbol: Hz) is the SI unit of frequency. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... The newton (symbol: N) is the SI unit of force. ... In physics, force is an influence that may cause a body to accelerate. ... A spring scale measures the weight of an object In the physical sciences, weight is a measurement of the gravitational force acting on an object. ... The joule (IPA pronunciation: or ) (symbol: J) is the SI unit of energy. ... Mechanical work is a force applied through a distance, defined mathematically as the line integral of a scalar product of force and displacement vectors. ... In physics, heat, symbolized by Q, is defined as transfer of thermal energy [1] Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. ... The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ... In physics, power (symbol: P) is the rate at which work is performed or energy is transferred. ... Luminous flux or luminous power is the measure of the perceived power of light. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... Stress is the internal distribution of force per unit area that balances and reacts to external loads applied to a body. ... The lumen (symbol: lm) is the SI unit of luminous flux. ... Luminous flux is a measure of the energy emitted by a light source in all directions. ... The lux (symbol: lx) is the SI derived unit of illuminance or illumination. ... Illuminance is the total luminous flux incident per unit area. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... flux in science and mathematics. ... Josephson junction array chip developed by NIST as a standard volt. ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ... Electromotive force (emf) is the amount of energy gained per unit charge that passes through a device in the opposite direction to the electric field existing across that device. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... It has been suggested that Electric reactance be merged into this article or section. ... Examples of various types of capacitors. ... Capacitance is the ability of a capacitor to store potential difference or voltage for a given amount of stored charge. ... This article is in need of attention. ... Magnetic flux, represented by the Greek letter Φ known as phi, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... SI unit. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic field. ... An inductor. ... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ... Electrical conductance is an electrical phenomenon where a material contains movable particles with electric charge, which can carry electricity. ... The becquerel (symbol Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... The gray (symbol: Gy) is the SI unit of absorbed dose. ... Absorbed dose is a measure of the energy deposited in a medium by ionising radiation. ... Radiation hazard symbol. ... The sievert (symbol: Sv) is the SI derived unit of dose equivalent. ... The equivalent dose is a measure of the radiation dose to tissue where an attempt has been made to allow for the different relative biological effect of different types of radiation. ... Katal is the SI derived unit for catalytic activity. ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. ...

Other quantities and units

Compound units derived from SI units
Name Symbol Quantity Expression in terms
of SI base units
square metre m2 area m2
cubic metre m3 volume m3
metre per second m·s−1 speed, velocity m·s−1
metre per second squared m·s−2 acceleration m·s−2
metre per second cubed m·s−3 jerk m·s−3
radian per second rad·s−1 angular velocity s−1
newton second N·s momentum, impulse kg·m·s−1
newton metre second N·m·s angular momentum kg·m2·s−1
newton metre N·m torque, moment of force kg·m2·s−2
reciprocal metre m−1 wavenumber m−1
kilogram per cubic metre kg·m−3 density, mass density kg·m−3
cubic metre per kilogram kg−1·m3 specific volume kg−1·m3
mole per cubic metre m−3·mol amount (-of-substance) concentration m−3·mol
cubic metre per mole m3·mol−1 molar volume m3·mol−1
joule per kelvin J·K−1 heat capacity, entropy kg·m2·s−2·K−1
joule per kelvin mole J·K−1·mol−1 molar heat capacity, molar entropy kg·m2·s−2·K−1·mol−1
joule per kilogram kelvin J·K−1·kg−1 specific heat capacity, specific entropy m2·s−2·K−1
joule per mole J·mol−1 molar energy kg·m2·s−2·mol−1
joule per kilogram J·kg−1 specific energy m2·s−2
joule per cubic metre J·m−3 energy density kg·m−1·s−2
newton per metre N·m−1 = J·m−2 surface tension kg·s−2
watt per square metre W·m−2 heat flux density, irradiance kg·s−3
watt per metre kelvin W·m−1·K−1 thermal conductivity kg·m·s−3·K−1
square metre per second m2·s−1 kinematic viscosity, diffusion coefficient m2·s−1
pascal second Pa·s = N·s·m−2 dynamic viscosity kg·m−1·s−1
coulomb per cubic metre C·m−3 electric charge density m−3·s·A
ampere per square metre A·m−2 electric current density A·m−2
siemens per metre S·m−1 conductivity kg−1·m−3·s3·A2
siemens square metre per mole S·m2·mol−1 molar conductivity kg-1·s3·mol−1·A2
farad per metre F·m−1 permittivity kg−1·m−3·s4·A2
henry per metre H·m−1 permeability kg·m·s−2·A−2
volt per metre V·m−1 electric field strength kg·m·s−3·A−1
ampere per metre A·m−1 magnetic field strength A·m−1
candela per square metre cd·m−2 luminance cd·m−2
coulomb per kilogram C·kg−1 exposure (X and gamma rays) kg−1·s·A
gray per second Gy·s−1 absorbed dose rate m2·s−3
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A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... Area is a physical quantity expressing the size of a part of a surface. ... The cubic meter (symbol m³) is the SI derived unit of volume. ... The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. ... Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ... Speed is the rate of motion, or equivalently the rate of change of position, many times expressed as distance d moved per unit of time t. ... The velocity of an object is its speed in a particular direction. ... Meters per second squared is the SI derived unit of acceleration, defined by distance or displacement in metres divided by time in seconds and again divided by time in seconds. ... Acceleration is the time rate of change of velocity, and at any point on a velocity-time graph, it is given by the slope of the tangent to that point In physics or physical science, acceleration (symbol: a) is defined as the rate of change (or derivative with respect to... Look up jerk, jolt, surge, lurch in Wiktionary, the free dictionary. ... Angular velocity describes the speed of rotation and the orientation of the instantaneous axis about which the rotation occurs. ... In classical mechanics, momentum (pl. ... In classical mechanics, the impulse of a constant force is the product of the force and the time during which it acts. ... This gyroscope remains upright while spinning due to its angular momentum. ... It has been suggested that this article or section be merged with Moment (physics). ... Wavenumber in most physical sciences is a wave property inversely related to wavelength, having SI units of reciprocal meters (m−1). ... Kilogram per cubic metre is the SI measure of density and is represented as kg/m³, where kg stands for kilogram and m³ stands for cubic metre. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... To meet Wikipedias quality standards, this article or section may require cleanup. ... Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... Specific heat capacity, also known simply as specific heat (Symbol: C or c) is the measure of the heat energy required to raise the temperature of a given amount of a substance by one degree. ... In physics, surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... The related Category:Units of viscosity has been nominated for deletion, merging, or renaming. ... This article or section does not adequately cite its references or sources. ... The pascal second (symbol Pa·s) is the SI unit of dynamic viscosity. ... The related Category:Units of viscosity has been nominated for deletion, merging, or renaming. ... Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. ... It has been suggested that optical field be merged into this article or section. ... For other senses of this term, see magnetic field (disambiguation). ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ...

See also

Look up si, Si, SI in Wiktionary, the free dictionary. ... The SI system of units defines seven SI base units: physical units defined by an operational definition. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... In physics, Planck units are physical units of measurement defined exclusively in terms of the five universal physical constants shown in the table below in such a manner that all of these physical constants take on the numerical value of one when expressed in terms of these units. ...

References

  • I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC: Quantities, Units and Symbols in Physical Chemistry, 2nd edition (June 1993), Blackwell Science Inc (p. 72)

  Results from FactBites:
 
Essentials of the SI: Base & derived units (468 words)
Examples of such SI derived units are given in Table 2, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted.
In photometry, the unit name steradian and the unit symbol sr are usually retained in expressions for derived units.
For a graphical illustration of how the 22 derived units with special names and symbols given in Table 3 are related to the seven SI base units, see relationships among SI units.
SI derived unit - Wikipedia, the free encyclopedia (327 words)
SI derived units are part of the SI system of measurement units and are derived from the seven SI base units.
The unit of angle is the angle subtended at the centre of a circle by an arc of the circumference equal in length to the radius of the circle.
The unit of solid angle is the solid angle subtended at the centre of a sphere of radius r by a portion of the surface of the sphere having an area r
  More results at FactBites »


 

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