NEET Physics Notes Mechanics-Behaviour of Perfect Gas and Kinetic-Law of Equipartition of Energy
Law of Equipartition of Energy
Law of Equipartition of Energy
According to law of equipartition of energy for any system in thermal equilibrium, the total energy is equally distributed among its various degree of freedom and each degree of freedom is associated with energy
(where, k = 1.38 x 10~23 J/K.
T = absolute temperature of the system).
Specific Heat Capacities of Gases
The specific heat of gas can have many values, but out of them following two values are important
Specific Heat at Constant Volume
The specific heat of a gas at constant volume is defined as the quantity of heat required to raise the temperature of unit mass of gas through 1°C or 1 K when its volume is kept constant i.e.
Specific Heat at Constant Pressure
The specific heat of a gas at constant pressure is defined as the quantity of heat required to raise the temperature of unit mass of gas through IK, when its pressure is
kept constant
Specific heat of a gas at constant pressure is greater than the specific heat at constant volume i.e. Cp >CV.
Cp and CV are related to each other according to relation,
Eq. (ii) is called Mayer’s relation.
If Cp and CV are measured in the units of work and R is also in the units of work (or energy), then Eq. (ii) becomesCp -Cv =R..
Specific Heat in Terms of Degree of Freedom
For a gas at temperature T, the internal energy
Mean Free Path
Every gas consists of a very large number of molecules. These molecules are in a state of continuous rapid and random motion. They undergo perfect elastic collisions against one another. Therefore, path of a single gas molecule consists of a series of short zig-zag paths of different lengths.
The mean free path of a gas molecule is the average distance between two successive collisions.
Here, α= diameter of the molecule and n = number of molecules per unit volume.