S.I. Units of Physical Quantity

S.I. Units of Physical Quantity

Unit-The chosen standard used for measuring a physical quantity is called unit.
Unit should be:

• Well defined
• Easy to reproduce
• Easy to compare
• Internationally accepted
• Independent of changes in physical conditions

Units are of two types:

1. Fundamental Unit :
   • Are expressed in terms of standard units.
   • There are seven (7) basic physical quantities.
   • Examples- mass, length, time, electric current, temperature, luminous intensity and amount of substance.
   • All other quantities are expressed in terms of these quantities.
2. Derived Unit :
   • When a physical quantity expresses itself in terms of two or more fundamental physical quantities.
   • It is derived by multiplying or dividing one basic physical quantity with another basic physical quantity.
   • Examples- density, volume, force, power, velocity, acceleration etc.

System of Units –Units depends on choice .each choice of units leads to a new system of units. The internationally accepted systems are
i) CGS System          ii) MKS System        iii) FPS System    iv) SI Units.
In SI Units(International System of Units)- There are seven fundamental units and 2 supplementary units.All the units which are defined/ expressed in terms of fundamental units are called derived units.such as force work etc.
Here list of most often used physical quantities their unit and symbols.

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