public Class Units

The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10⁻¹⁹ when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs. This definition implies the exact relation e = 1.602 176 634 × 10⁻¹⁹ A s. Inverting this relation gives an exact expression for the unit ampere in terms of the defining constants e and ∆νCs: 1 A = (e / 1.602 176 634 × 10⁻¹⁹) s⁻¹

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SI Base Unit

The SI unit for activity of a radionuclide (standard name Bq ). One becquerel is the radiation caused by one disintegration per second. It is named after the French physicist, Antoine-Henri Becquerel (1852-1908).

The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10¹² Hz, Kcd, to be 683 when expressed in the unit lm W−1, which is equal to cd sr W⁻¹, or cd sr kg⁻¹ m⁻² s³, where the kilogram, metre and second are defined in terms of h, c and ∆νCs. This definition implies the exact relation Kcd = 683 cd sr kg⁻¹ m⁻² s³ for monochromatic radiation of frequency ν = 540 × 10¹² Hz. Inverting this relation gives an exact expression for the candela in terms of the defining constants Kcd, h and ∆νCs: 1 cd = (Kcd / 683) kg m² s⁻³ sr⁻¹

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SI Base Unit

See Also

Wikipedia: Candela

The SI unit for Celsius temperature (standard name °C). This is a unit of temperature such as the freezing point of water (at one atmosphere of pressure) is 0 °C, while the boiling point is 100 °C.

The SI unit for electric charge, quantity of electricity (standard name C). One Coulomb is equal to the quantity of charge transferred in one second by a steady current of one ampere. It is named after the French physicist Charles Augustin de Coulomb (1736-1806).

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SI Brochure - Table 4

The SI unit for volume quantities (standard name m3).

A time unit accepted for use with SI units (standard name d ).

The SI unit for capacitance (standard name F). One Farad is equal to the capacitance of a capacitor having an equal and opposite charge of 1 coulomb on each plate and a potential difference of 1 volt between the plates. It is named after the British physicist and chemist Michael Faraday (1791-1867).

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SI Brochure - Table 4

The SI derived unit for mass quantities (standard name g). The base unit for mass quantity is KILOGRAM.

The SI unit for absorbed dose, specific energy (imparted), kerma (standard name Gy). One gray is equal to the dose of one joule of energy absorbed per one kilogram of matter. It is named after the British physician L. H. Gray (1905-1965).

The alternate unit for inductance (standard name H). One Henry is equal to the inductance for which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. It is named after the American physicist Joseph Henry (1791-1878).

The SI unit for frequency (standard name Hz). A unit of frequency equal to one cycle per second. After Heinrich Rudolf Hertz (1857-1894), German physicist who was the first to produce radio waves artificially.

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SI Brochure - Table 4

A time unit accepted for use with SI units (standard name h ).

The SI unit for energy, work, quantity of heat (J). One joule is the amount of work done when an applied force of 1 newton moves through a distance of 1 metre in the direction of the force. It is named after the English physicist James Prescott Joule (1818-1889).

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SI Brochure - Table 4

The SI unit for catalytic activity (standard name kat).

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SI Brochure - Table 4

The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 × 10−²³ when expressed in the unit J K⁻¹, which is equal to kg m² s⁻² K⁻¹, where the kilogram, metre and second are defined in terms of h, c and ∆νCs. This definition implies the exact relation k = 1.380 649 × 10⁻²³ kg m² s⁻² K⁻¹. Inverting this relation gives an exact expression for the kelvin in terms of the defining constants k, h and ∆νCs: 1 K = (1.380 649 / k) × 10⁻²³ kg m² s⁻²

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SI Base Unit

See Also

JOULE

The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10⁻³⁴ when expressed in the unit J s, which is equal to kg m² s−1, where the metre and the second are defined in terms of c and ∆νCs. This definition implies the exact relation h = 6.626 070 15 × 10−34 kg m² s⁻¹. Inverting this relation gives an exact expression for the kilogram in terms of the three defining constants h, ∆νCs and c: 1 kg = (h / 6.626 070 15 × 10⁻³⁴) m⁻² s

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SI Base Unit

See Also

Wikipedia: Kilogram, GRAM, METRE, SECOND

A unit of speed expressing the number of international kilometres per hour (abbreviation km/h).

See Also

Wikipedia: Kilometres per hour

A volume unit accepted for use with SI units (standard name l).

See Also

Wikipedia: Litre

The SI unit for luminous flux (standard name lm). One Lumen is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

The SI unit for illuminance (standard name lx). One Lux is equal to one lumen per square metre.

The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m s⁻¹, where the second is defined in terms of the caesium frequency ∆νCs. This definition implies the exact relation c = 299 792 458 m s⁻¹. Inverting this relation gives an exact expression for the metre in terms of the defining constants c and ∆νCs: 1 m = (c / 299 792 458)s = 9 192 631 770 c / 299 792 458 ∆νCs ≈ 30.663 319 c / ∆νCs

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SI Base Unit

The SI unit for speed quantities (standard name m/s).

The SI unit for acceleration quantities (standard name m/s2).

See Also

Wikipedia: Metre per second squared

A time unit accepted for use with SI units (standard name min).

The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 10²³ elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol⁻¹ and is called the Avogadro number. The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles. This definition implies the exact relation Nₐ = 6.022 140 76 × 10²³ mol⁻¹. Inverting this relation gives an exact expression for the mole in terms of the defining constant NA: 1 mol = 6.02214076 × 10²³ / Nₐ

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SI Base Unit

A unit of duration equal to 1/12 YEAR (common name mo).

Since

2.3

The SI unit for force (standard name N). One newton is the force required to give a mass of 1 kilogram an Force of 1 metre per second per second. It is named after the English mathematician and physicist Sir Isaac Newton (1642-1727).

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SI Brochure - Table 4

The SI unit for electric resistance (standard name Ohm). One Ohm is equal to the resistance of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals. It is named after the German physicist Georg Simon Ohm (1789-1854).

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SI Brochure - Table 4

The SI unit for pressure, stress (standard name Pa). One pascal is equal to one newton per square meter. It is named after the French philosopher and mathematician Blaise Pascal (1623-1662).

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SI Brochure - Table 4

A dimensionless unit accepted for use with SI units (standard name %).

The SI unit for plane angle quantities (standard name rad). One radian is the angle between two radii of a circle such that the length of the arc between them is equal to the radius.

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SI Brochure - Table 4

The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ∆νCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s⁻¹. This definition implies the exact relation ∆νCs = 9 192 631 770 Hz. Inverting this relation gives an expression for the unit second in terms of the defining constant ∆νCs: 1 Hz = ∆νCs / 9 192 631 770 or 1 s = 9 192 631 770 / ∆νCs

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SI Base Unit

The SI unit for electric conductance (standard name S). One Siemens is equal to one ampere per volt. It is named after the German engineer Ernst Werner von Siemens (1816-1892).

The SI unit for dose equivalent (standard name Sv). One Sievert is equal is equal to the actual dose, in grays, multiplied by a "quality factor" which is larger for more dangerous forms of radiation. It is named after the Swedish physicist Rolf Sievert (1898-1966).

The SI unit for area quantities (standard name m2).

See Also

Wikipedia: Square metre

The SI unit for solid angle quantities (standard name sr). One steradian is the solid angle subtended at the center of a sphere by an area on the surface of the sphere that is equal to the radius squared. The total solid angle of a sphere is 4*Pi steradians.

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SI Brochure - Table 4

The alternate unit for magnetic flux density (standard name T). One Tesla is equal equal to one weber per square metre. It is named after the Serbian-born American electrical engineer and physicist Nikola Tesla (1856-1943).

The SI unit for electric potential difference, electromotive force (standard name V). One Volt is equal to the difference of electric potential between two points on a conducting wire carrying a constant current of one ampere when the power dissipated between the points is one watt. It is named after the Italian physicist Count Alessandro Volta (1745-1827).

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SI Brochure - Table 4

The SI unit for power, radiant, flux (standard name W). One watt is equal to one joule per second. It is named after the British scientist James Watt (1736-1819).

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SI Brochure - Table 4

The SI unit for magnetic flux (standard name Wb). One Weber is equal to the magnetic flux that in linking a circuit of one turn produces in it an electromotive force of one volt as it is uniformly reduced to zero within one second. It is named after the German physicist Wilhelm Eduard Weber (1804-1891).

A unit of duration equal to 7 DAY (common name wk).

A time unit accepted for use with SI units (standard name yr ).