SI system principle is that there should be only one unit of measure per greatness and derivations between units should if possible be using a conversion factor first
The basic units in the SI system are all well defined and used by themselves as well as to derive the other devices that are used in many different areas.
Is defined as the distance that light travels in 1/299792458 seconds in a total vacuum.
The unit kg is equal to the mass of the international prototype kilogram kept at the BIPM (International Bureau of Weights and Measures) outside Paris. The weight is made of a mixture of 90% platinum and 10% iridium.
time of 9,192,631,770 periods of the radiation corresponding to the transition between two energy levels of the ground state of the isotope cesium-133.
The strength of a constant electrical current as it passes two infinitely long straight parallel conductors placed in vacuum at a distance of 1m apart causing power 2x10 -7 newtons.
Is defined as 1 / 273.16 of the thermodynamic temperature of the triple point of water, ie the point where the three phases of liquid, gas and solid can coexist.
Is defined as the light intensity in a given direction, of a source that emits monochromatic radiation with a frequency of 540 * 10 12 sup> hertz and with a radiant intensity of 1/683 watt per steradian.
The amount of substance of a system which contains as many elementary units as there are atoms in 0.012 kg of carbon-12