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MEASUREMENT UNITS AND CONVERSION

| Quantity |
Unit |
Symbol |
Definition |
| Length |
metre |
m |
The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. |
| Mass |
kilogram |
kg |
The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. |
| Time |
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 caesium 133 atom. |
| Electric current |
ampere |
A |
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10-7 newton per metre of length. |
| Thermodynamic temperature |
kelvin |
K |
The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. |
| Amount of substance |
mole |
mol |
- The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12.
- When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
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| Luminous intensity |
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. |
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