Class 11 physics chapter 2 unit and dimension

 1.Physical Quantity: A property that can be measured and described by a numerical value is called a physical quantity.

Fundamental and Derived Quantities:

2.Fundamental Quantities: Basic quantities like length, mass, time, electric current, temperature, amount of substance, and luminous intensity.

Derived Quantities: Quantities derived from fundamental quantities. Example: velocity, acceleration, force, etc.

Units: Standards used for measuring physical quantities are called units. They provide a standard of comparison.

3.SI Units: Internationally accepted system of units (e.g., meter, kilogram, second, ampere, kelvin, mole, candela).

Dimensions:

Every physical quantity can be expressed in terms of fundamental quantities.

The dimensions of a physical quantity are the powers to which the fundamental quantities are raised to represent that quantity.

Dimensional Analysis:

Used to check the correctness of equations and to derive new relations.

Involves analyzing the dimensions of each term in an equation and ensuring they are consistent on both sides.

Dimensional Formulae:

Written using square brackets [] to denote dimensions.

Example: Dimensional formula of velocity = [LT⁻¹] (Length/Time).

Dimensional Homogeneity:

For an equation to be dimensionally correct, the dimensions of each term on both sides must be the same.

Helps in identifying errors and inconsistencies in equations.

Limitations of Dimensional Analysis:

Cannot give information about dimensionless constants.

Cannot differentiate between different physical quantities having the same dimensions.

Uses of Dimensional Analysis:

4.Checking the correctness of equations.

Deriving relationships between physical quantities.

Simplifying complex equations.

Predicting the behavior of physical systems.

These notes should provide you with a basic understanding of Unit and Dimensions in physics for your Class 11 studies.