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Thermal Physics

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21 Jan 2008 16:12:26 IST

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Degree of freedom???

None

what do we xactly mean by the degree of freedom..

n how do we calculate it??

what wud b the degree of freedom for a TRI ATOMIC (linear) molecule?

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Ashwin R

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Joined: 27 Dec 2007

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21 Jan 2008 16:29:27 IST

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(In general, ?degrees of freedom? refers to the number
of independent means by which a molecule can possess energy)..
it can be of three types..
translational
rotational
vibrational.....
........................................................................................................
it can be found using the relation
n=3N-r
where
n is degrees of freedom
N=number of molecules
r=independent relation betwe en constituent atoms
..........................................................................................................
for tri atomic gas with linear structures
N=3
r=2
substituting in the eqn we get 'n'=7

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NITESH BASKARAN

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21 Jan 2008 18:36:42 IST

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the total internal energy of a molecule is stored is a sum total of three types of energies

1. translational kinetic energy

2. rotational kinetic energy

3. vibrational energy

now any molecule can move either in x direction or in y direction or in z direction
hence we can separately consider energies in these three directions
for a tri atomic linear molecule
in addition to this eneergy there is also rotaional energy along two directions ( along its axis rotation is negligeble)

so now there sre 5 ways of storing energy
also there is vibrational energy in addition to these to energies
which can also exist in two ways ( one due to first two molecules and other due to last two molecules)
hence there are seven ways of storing energy
theis is the degree of freedom of the given gas

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