Units
A unit is an internationally accepted standard for measurements of quantities .
o Measurement consists of a numeric quantity along with a relevant unit .
o Units for Fundamental or base quantities ( like length , time etc .) are called Fundamental units . o Units which are combination of fundamental units are called Derived units . o Fundamental and Derived units together form a System of Units . o Internationally accepted system of units is SystèmeInternationale d ’ Unites ( French for International system of Units ) or SI . It was developed and recommended by General Conference on Weights and Measures in 1971 . o SI lists 7 base units as in the table below . Along with it , there are two units - radian or rad ( unit for plane angle ) and steradian or sr ( unit for solid angle ). They both are dimensionless .
Base Quantity Name Symbol Length metre m
Mass kilogram kg
Time second s
Electric Current ampere A
Thermo dynamic |
|
|
Temperature |
kelvin |
K |
Amount of Substance mole mol
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