CORE UNITS
Meter (m) is the length of the path traveled in a vacuum by light during a time of 1 / 299
792 458 seconds.
kilogram (kg) is the mass of the international prototype of platinum-iridium kept in the
Office of Weights and Measures in Paris.
Second (s) Unit of time is defined as the duration of 9 192 631 770 periods of the
radiation corresponding to the transition between two hyperfine levels of the ground state of
atom of cesium 133.
ampere (A) is the intensity of constant current that, maintained in two straight conductor,
parallel, of infinite length, of negligible circular cross section and placed at a distance of one
meters of each other in the void between these conductors a force equal to 2 ⋅ 10
-7 N per meter of length.
kelvin (K) Unit of thermodynamic temperature corresponding to the fraction 1 / 273 of 16
thermodynamic temperature of the triple point of water.
candela (cd) Unit of luminous intensity, corresponding to a radiation source that emits
monochromatic frequency 540 ⋅ l0
l2 Hz and whose energy intensity in that direction is 1 / 683
W sr-1
.
mole (mol) Amount of substance of a system which contains as many elementary entities
there are atoms in 0.012 kg of carbon 12.
DERIVED UNITS
Coulomb (C) Amount of electricity transported in one second by a current of a
ampere.
joule (J) Work produced by a force of one newton when its point of application is
moved the distance of one meter in the direction of force.
NEWTON (N) is the force applied to a body that has a mass of 1 kilogram, it
announced an acceleration of 1 meter per second every second.
pascal (Pa) Unit of pressure. Is the uniform pressure acting on a flat surface
1 meter square, perpendicular to the surface exerts a total force of 1 newton.
volt (V) Unit voltage, electric potential, electromotive force. Is the difference
electric potential between two points on a thread that carries a stream of
intensity of 1 ampere when the power dissipated between these points is equal to 1 watt.
watt (W) power that gives rise to an energy output equal to 1 joule per second.
ohm (Ω) Unit of electrical resistance. Is the electrical resistance between two points
a conductor when a potential difference of 1 volt applied between these two
items produced in that conductor, a current intensity of 1 ampere, when no force
electromotive the driver.
weber (Wb) Unit of magnetic flux, flux of magnetic induction. Is the magnetic flux that, when
through a circuit of one turn produces in it an electromotive force of 1 volt if
annulling the flow uniformly decrease by 1 seconds.