NCERT Solutions for Class 11 Physics Chapter 13 Kinetic Theory


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NCERT Solutions for Class 11 Physics Chapter 13 Kinetic Theory: Consider a layer inside a container filled with gas. The layer of gas inside the volume of a container is in equilibrium because the pressure is the same on both sides of the layer. That is a gas in a container of gas the pressure exists everywhere in the fluid not only at the walls of the container. The pressure is due to the rapidly moving molecules of gas. Unlike solids and liquids, the interatomic force in gases is less. NCERT Solutions for Class 11 Physics Chapter 13 Kinetic Theory explains the behavior of gases based on the idea that the gas consists of rapidly moving molecules.

Maxwell, Boltzmann, and others developed the Kinetic theory of gas in the 19th century. The kinetic theory interprets the pressure and temperature at the molecular level. Kinetic theory is consistent with gas laws and it correctly explains specific heat and relates measurable properties of gases such as viscosity, diffusion, etc. The NCERT Solutions for Class 11 Physics Chapter 13 gives an introduction to the Kinetic Theory of gases. 

The main topics of  NCERT Class 11 Physics Chapter 13 are listed below.

13.1 Introduction

13.2 Molecular nature of matter

13.3 Behaviour of gases

13.4 Kinetic theory of an ideal gas

13.5 Law of equipartition of energy

13.6 Specific heat capacity

13.7 Mean free path

A brief summary of formulas of  NCERT Class 11 Physics Chapter 13 are given below 

  • The ideal gas equation is given by

 PV=\mu RT=K_BNT

where \mu is the number of moles

N is the number of molecules

 R and kB are universal constants.

  • The pressure of an ideal gas

            P=\frac{1}{3}nm\bar v^2

where n is the number density, m is the mass of the molecule and \bar v^2 is the mean of the squared speed. 

  • The rms velocity of the gas molecule

           v_{rms}=\sqrt{\bar v^2}=\sqrt{\frac{3K_BT}{m}} Where T is the temperature.

  • The translational kinetic energy is


  • The mean free path

           l=\frac{1}{\sqrt{2}n\pi d^2} 

     where n is the number density and d is the diameter of the molecule

The NCERT exercise of Kinetic Theory consists of 14 questions. The NCERT Solutions for Class 11 Physics Chapter 13 Kinetic Theory are given below:

Q-13.1 Estimate the fraction of molecular volume to the actual volume occupied by oxygen gas at STP. Take the diameter of an oxygen molecule to be 3 Å.

NCERT Solutions for class 11 Physics


Physical world


Units and Measurement


Motion in a straight line


Motion in a Plane


Laws of Motion


Work, Energy and Power


System of Particles and Rotational motion




Mechanical Properties of Solids


Mechanical Properties of Fluids


Thermal Properties of Matter








NCERT Solutions for Class 11- Subject wise

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NCERT solutions for Class 11 Maths

NCERT solutions for Class 11 Chemistry

NCERT solutions for Class 11 Physics


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