###
Degree of freedom & first law thermodynamic

__Degree of freedom__

These are the total number of independent coordinate a body can have
Or
Total number of method of exchanging energy

For monoatomic gases
Size of particle is very-2 small ,so it does not have ratational
Kenetic energy.

It has only 3-direction x,y,z
Through which it can exchange energy

For diatomic gas
It has 3-translational and 2-rotational through which it can exchange energy

For triangular gas

It can 3-translational and 3-rotational method through which it can exchange energy

Now we will discucuss
.....................

__Law of equipartition of energy__

It means energy distribution in all direction will same
(in x , y , z direction energy will be same)

For monoatomic gases
In x-direction energy = kt/2
In y-direction energy = kt/2
In z-direction energy = kt/2
So here we can write total energy = kt/2+kt/2+kt/2
=3kt/2

**Note-**
Energy of rotation is equal to energy of transnational motion

Now we will talk about the first law of thermodynamic

Ques rises what is first law thermodynamic

__first law of thermodynamics states that the increase in __**internal energy** is equal to the total heat added and work done by the surroundings.

it can be well understood by observing below

Now
thermodynamical system- It is system that can Represent in term of Thermodynamical co-ordinate

There are three thermodynamical constant
Pressure
Volume
Temp

Pressure can be measure by putting are applying pressure at equilibrium
i.e applied pressure = internal Pressure