Class 11 Physics Notes Units and Measurement | NCERT Solutions 11th Science
In this article, we have discussed the Units and Measurement, it covers the Chapter 2: Units and Measurement of Physics Class 11.
Quantities that can be measured, in term of which, laws of Physics can be defined are called physical quantities. Example: mass, length etc.
Measurement of any physical quantity involves comparison with any certain basic, arbitrarily chosen, internationally accepted reference standard known as a unit.
Watch recorded lectures on Class 11 Physics – Units and Measurement.
Fundamental (or Base) units & Derived units:
The units for the base or fundamental quantities are called base or fundamental units.
There are 7 fundamental quantities and they are:
- Electric Current
- Amount of Substance
- Luminous Intensity
The units of all other physical quantities can be expressed as combinations of the base units. Such units obtained for the derived quantities are called derived units.
For the detailed explanation, click on Physics notes of Class 11.
The system of Units:
A complete set of units, both the base units and derived units, is known as the system of units.
Three common systems of units frequently used in Physics are:
- CGS system (In CGS system, we use centimeter, gram and second respectively)
- FPS (or British) system (In FPS system, we use foot, pound and second respectively)
- MKS system (In MKS system, we use metre, kilogram and second respectively)
- SI System of Unit
The system of units which at present is internationally accepted for measurement is known as the SI system of Units.
SI units used decimal system; conversions within the system are quite simple and convenient.
SI units of 7 Fundamental & 2 Supplementary Physical Quantities:
SI units of 7 Fundamental Physical Quantities
Base quantity Name (& Symbol) of SI Units
Length metre (m)
Mass kilogram (kg)
Time second (s)
Electric current Ampere
Temperature Kelvin (k)
Amount of substance mole (mol)
Luminous intensity candela (cd)
SI units of 2 Supplementary Physical Quantities
Plane angle Radian (rad)
Solid angle Steradian (sr)
In 11th Science, you can read another note, NCERT Solutions for Class 11 Physics
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Tags: Units and measurement, physical qualities, fundamental units & derived units, systems of unit.