JEE Main & Advanced Chemistry Units for measurement

Units for measurement             

The chosen standard of measurement of a quantity which has essentially the same nature as that of the quantity is called the unit of the quantity. Following are the important types of system for unit,           

(1) C.G.S. System : Length (centimetre), Mass (gram), Time (second)           

(2) M.K.S. System : Length (metre), Mass (kilogram), Time (second)           

(3) F.P.S. System  : Length (foot), Mass (pound),      Time (second)           

(4) S.I. System : The 11th general conference of weights and measures (October 1960) adopted International system of units, popularly known as the SI units. The SI has seven basic units from which all other units are derived called derived units. The standard prefixes which helps to reduce the basic units are now widely used. Dimensional analysis : The seven basic quantities lead to a number of derived quantities such as pressure, volume, force, density, speed etc. The units for such quantities can be obtained by defining the derived quantity in terms of the base quantities using the base units. For example, speed (velocity) is expressed in distance/time. So the unit is \[m/s\] or \[m{{s}^{-1}}\]. The unit of force \[\text{(mass}\times \text{ acceleration)}\] is \[kg\ m{{s}^{-2}}\] and the unit for acceleration is \[m{{s}^{-2}}\].

Seven basic S.I. units

Derived Units

Standard prefixes use to reduce the basic units

Conversion factors