Physics > Unit and Dimensions > 3.0 SI units
Unit and Dimensions
1.0 Introduction
2.0 Physical quantity
3.0 SI units
3.1 Definition of standard units
3.2 System of units
3.3 Rules for writing units
3.4 Characteristics of a standard unit
3.5 Advantages of SI
4.0 SI prefixes
5.0 Conversion of units
6.0 Important practical units
7.0 Dimensions
8.0 Dimensional formula
9.0 Dimensional equation
10.0 List of dimensional formula
11.0 Application of dimensional analysis
11.1 To check the dimensional consistency of equations
11.2 To deduce relation among the physical quantities
11.3 To convert one system of unit into another system of unit
12.0 Limitations of dimensional analysis
3.2 System of units
3.2 System of units
3.3 Rules for writing units
3.4 Characteristics of a standard unit
3.5 Advantages of SI
11.2 To deduce relation among the physical quantities
11.3 To convert one system of unit into another system of unit
| System of units | Length | Mass | Time |
| MKS | metre | kilogram | second |
| CGS | centi-metre | gram | second |
| FPS | foot | pound | second |
S.I. (System International units):
This system is an improved and extended version of M.K.S. system. SI system defines seven fundamental quantities and two supplementary quantities.
Seven fundamental quantities
| S. No. | Quantity | SI Unit | Symbol |
| 1. | Length | metre | $m$ |
| 2. | Mass | kilogram | $kg$ |
| 3. | Time | second | $s$ |
| 4. | Electric current | ampere | $A$ |
| 5. | Thermodynamic temperature | kelvin | $K$ |
| 6. | Luminous intensity | candela | $cd$ |
| 7. | Amount of substance | mole | mol |
Two supplementary quantities
| S. No. | Quantity | SI Unit | Symbol |
| 1. | Angle | radian | rad |
| 2. | Solid angle | steradian | sr |
