2. Unit and measurement


Physics describes the laws of nature. This description is quantitative and involves measurement and comparison of physical quantities. To measure a physical quantity we need some standard unit of that quantity.

 We can define a set of fundamental 
quantities as follows : 
(a) The fundamental quantities should be indepen￾dent of each other, and 
(b) All other quantities may be expressed in terms 
of the fundamental quantities. 

Quantity  Name of unit symbol
Mass kilogram k
Length metre m
Time second s
Current ampere A
Amount of substance  mole mol
Temperature  Kelvin K
Intensity  candela cd

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