m
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@sdZdkTedddZZZedddZZedd d
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ZedddZedddZZedddZZedddZZedZdedZeeZZeedZZd eZZeeZZeeedZ Z!e!eZ"Z#e#eZ$Z%e!edZ&Z'e'eZ(Z)e#eZ*Z+e#eZ,Z-e+eZ.d e.Z/Z0ee.Z1Z2e-eZ3Z4e-edZ5Z6ei7d!e8e9d"d#e:ed$d%e8e9d&d'e;eed(d)d*e8e9d+d#e<eed,ei7d-e8d ei=ei>d.d/ei?d0S(1s2The SI units.
See also units.py for a huge bestiary of other units; and
http://physics.nist.gov/cuu/Units/current.html
http://www.bipm.org/en/si/si_brochure/
for definitive sources of information about units.
Note that Quantity equips certain kinds of quantity with extra attributes:
time.light, mass.weight or mass.force, trigonometric attributes for angles,
their inverses and a few relatives for scalars, Centigrade and Fahrenheit
equivalents for temperatures. See quantity.py for details.
$Id: SI.py,v 1.14 2007/03/24 16:53:35 eddy Exp $
(t*tstsecondsThe SI base unit of time.
9192631770 periods of the radiation corresponding to the transition between
the two hyperfine levels of the ground state of the caesium-133 atom.tmtmetresThe SI base unit of length.
The length of the path travelled by light in vacuum during a time interval of
1/299792458 of a second. tkgt
kilogrammesThe SI base unit of mass.
The mass of the *International Prototype* kilogramme (a platinum-iridium
cylinder) kept in the Bureau International des Poids et Mesures (BIPM),
Sèvres, Paris.tAtAmperes-The SI base unit of electric current.
That constant current which, if maintained in two parallel rectilinear
conductors, of immense length and negligible circular cross-section, placed 1
metre apart in a vacuum, would produce a force between these conductors equal to
2e-7 newton per meter of length.tKtKelvinsThe SI base unit of temperature.
The fraction 1/273.16 (exactly) of the thermodynamic temperature at the triple
point of water. tmoltMolesAThe SI base unit of `amount of substance'.
The amount of substance which contains as many elementary units as there are
atoms in 12e-3 kilogrammes (exactly) of pure carbon-12. The elementary unit
must be specified and may be atom, molecule, ion, radical, electron, photon
*etc*. or collection of elementary units. tcdtCandelasThe SI base unit of luminous intensity.
The luminous intensity, in a given direction, of a source that emits
monochromatic radiation of frequency 540e12 Hz and that has a radiant intensity
in that direction of 1/683 W/sr.
[540 tera Hz light has a wavelength of 555 nm; the human eye's peak response is
to light with a wavelength of about 550 nm. An older variant of the definition
specified the candela as the luminous intensity, in the perpendicular direction,
of a surface of 1/60 square centimetere of a black body at the freezing (or,
equivalently, melting) temperature of platinum under a pressure of 101325 Pascal
(i.e. 1 atmosphere).]tradtRadiansThe SI supplementary unit of angle.
The angle subtended at the centre of a circle by an arc of the circumference
equal in length to the radius of the circle.tsrt SteradiansThe SI supplementary unit of solid angle.
The unit of solid angle is the solid angle subtended at the center of a sphere
of radius r by a portion of the surface of the sphere having area r*r.ii
iitAvogadrof602.20450000000005f0.0030000000000000001sAvogadro's numbertchargef96.484560000000002f0.00027tdocsFaraday's Constant
This is the charge per mole of protons; it is the charge transferred when
electrolysis liberates some univalent electrolyte, per mole liberated.
tvolumef22.413599999999999sMolar volume of an ideal gas at STP.
At standard temperature (zero Centigrade, 273.15 Kelvin) and pressure (one
atomosphere), one mole of any ideal gas will have a volume of 22.4136 litres.
Compare particle.Nucleon.amuk and mol.Loschmidt.
t LoschmidtsLoschmidt's number (gently rescaled).
Loschmidt's name is normally associated with the number of molecules (or atoms,
as appropriate) in one cubic centimetre of ideal gas under standard conditions;
however, since that makes it really a number per unit volume, I've gently
abridged the standard definition to give the number density of molecules (or
atoms); multiply this by cm**3 to get the orthodox number. tFaradayN(@t__doc__tquantityt base_unitRtsecRRRRtkilogramRRRR R
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