Electronic Automotive Handbook
Definitions of the base Sl units
1 meter is defined as the distance which light travels in a vacuum in 1/299,792,458 seconds (17th CGPM, 19831). The meter is therefore defined using the speed of light in a vacuum, c = 299,792,458 m/s, and no longer by the wavelength of the radiation emitted by the krypton nuclide 86Kr. The meter was originally defined as the forty- millionth part of a terrestrial meridian (standard meter, Paris, 1875).
1 kilogram is the mass of the international prototype kilogram (1st CGPM, 1889 and 3rd CGPM, 19011).
1 second is defined as 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 atoms of the 133Cs nuclide (13th CGPM, 1967.1)
1 ampere is defined as that constant electric current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-sections, and placed 1 meter apart in a vacuum will produce between these conductors a force equal to 2 · 10–7 N per meter of length (9th CGPM, 1948.1)
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