What is unit ? What are the requirement of standar unit.

 Unit  :- The reference standard used for measurement of a physical quantity is called unit of physical quantity.

• For Example :- Length of rod is 5m.

Here,  5m = 5 * 1m

• 1m is the standard (unit) used for measurement of lenght and 5 is mgnitude of lenght.

Requirement of standard unit

Requirement of good or standard unit such as given follow 

1. It should be well defined.
2. It shuld be easily reproduciable at all places .
3. It should not changed with space and time .
4. It should be easily comparable and readily available.
5. It should be universally accepted.
6. It should be such that the quantity measured with it should not be too large or too small.