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between the two hyperfine
levels of the ground state of

Cesium 133.

Given two parallel,
rectilinear conductors of
negligible circular cross-

section positioned 1 m apart
in vacuum, one ampere is the
electric current which,

Electric current ampere A passing through both of them,
makes them attract each other
-7
by the force of 2.10 newtons
per every meter of length.

This fixes the permeability of
-7
vacuum to exactly 2π*10
H/m.

One degree K equals

1/273.16 of the
Temperature kelvin K
thermodynamic temperature
of the triple point of water.

The amount of a substance
composed of as many
specified elementary units

Quantity of substance mole mol
(molecules, atoms) as there
are atoms in 0.012 kg of
Carbon 12.

The candle (or candela) is
the luminous intensity, in a
given direction, of a source
that emits monochromatic

Luminosity candle cd
radiation of frequency
12
540.10 hertz and that has a
radiant intensity in that
direction of 1/683 W/sr.

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