Definitions of SI Units
meter (m) The meter is the length equal to the distance traveled
by light, in vacuum, in a time of 1>299,792,458 second.
kilogram (kg) The kilogram is the unit of mass; it is defined
by taking the value of Planck’s constant h to be exactly
6.62607015 * 10-34 kg # m2>s.
second (s) The second is the duration of 9,192,631,770
periods of the radiation corresponding to the transition
between the two hyperfine levels of the ground state of the
ampere (A) The ampere is a current of one coloumb per second,
where the coulomb is defined in terms of the elementary
kelvin (K) The kelvin, unit of thermodynamic temperature,
is defined by taking the value of the Boltzmann constant k to be
exactly 1.380649 * 10-23 J>K.
ohm (_) The ohm is the electric resistance between two
points of a conductor when a constant difference of potential
of 1 volt, applied between these two points, produces in this
conductor a current of 1 ampere, this conductor not being the
source of any electromotive force.
coulomb (C) The coulomb is the quantity of electricity such
that the elementary charge e is exactly 1.602176634 * 10-19 C
transported in 1 second by a current of 1 ampere.
candela (cd) The candela is the luminous intensity, in a
given direction, of a source that emits monochromatic radiation
of frequency 540 * 1012 hertz and that has a radiant intensity
in that direction of 1>683 watt per steradian.
mole (mol) The mole is the SI unit of substance. One mole
contains exactly 6.02214076 * 1023 elementary entities.
newton (N) The newton is that force that gives to a mass of
1 kilogram an acceleration of 1 meter per second per second.
joule (J) The joule is the work done when the point of application
of a constant force of 1 newton is displaced a distance of 1 meter
in the direction of the force.
watt (W) The watt is the power that gives rise to the production
of energy at the rate of 1 joule per second.
volt (V) The volt is the difference of electric potential between
two points of a conducting wire carrying a constant current of
1 ampere, when the power dissipated between these points is
equal to 1 watt.
weber (Wb) The weber is the magnetic flux that, linking
a circuit of one turn, produces in it an electromotive force of
1 volt as it is reduced to zero at a uniform rate in 1 second.
lumen (lm) The lumen is the luminous flux emitted in a solid
angle of 1 steradian by a uniform point source having an intensity
of 1 candela.
farad (F) The farad is the capacitance of a capacitor between
the plates of which there appears a difference of potential of
1 volt when it is charged by a quantity of electricity equal to
henry (H) The henry is the inductance of a closed circuit in
which an electromotive force of 1 volt is produced when the
electric current in the circuit varies uniformly at a rate of 1 ampere
radian (rad) The radian is the plane angle between two radii
of a circle that cut off on the circumference an arc equal in
length to the radius.
steradian (sr) The steradian is the solid angle that, having its
vertex in the center of a sphere, cuts off an area of the surface
of the sphere equal to that of a square with sides of length equal
to the radius of the sphere.