Write the definitions of S.I base units

1. Kilogram (kg): The kilogram is the unit of mass or quantity of matter. lt may be defined
as the mass of the international prototype of the cylinder whose height and diameter are equal
and kept at Sevres near Paris.

2. Metre (m): The metre is the unit of length. It may be defined as the length equal to
16507.73 wave lengths in vacuum of the radiation corresponding to the transition between
the levels 2p10 and 5d5 of the Krypton-86 atom.

3. Second (s): The fundamental unit of time for all the systems is second, which is
1/ 24x60x60 = 1/86,400 th of the mean solar day. It may also be defined as the duration of
9192 63 1770 periods of the radiation corresponding to the transition between the two
hyperfine levels of the ground state of the Caesium-133 atom.

4. Kelvin (K): The kelvin is the unit of thermodynamic temperature. It may be defined as
the fraction 1/273·16 of the thermodynamic temperature of the triple point of water. The
temperature f°C implies that,

5. Ampere (A): The ampere is the unit of electric current. It may be defined as that constant
current, which, if maintained in two straight parallel conductors of infinite length, negligible
circular cross-section and placed 1 metre apart in vacuum, would produce between these
conductors a force equal to 2 x 10-7 newton per metre length.

6. Candela (cd): The candela is the unit of luminous intensity. It may be defined as the luminous
intensity in the perpendicular direction, of a surface of 1/600000 square metre of a black body
at the temperature of freezing platinum under a pressure of 101325 N m-2.

7. Mole (mol): The mole is the unit of the amount of substance. It may be defined as the
amount of substance of a system which contains as many elementary entities as there are
atoms in 0.012 kilogram of carbon-12.

The seven basic units are :

S.No.QuantityS.I. UnitsSymbol
5.Electric currentampereA
6.Luminous intensitycandelacd
7.Amount of substancemolemol

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