248 4 Thermodynamics and Statistical Physics
The Maxwell distribution
N(ν)dν= 4 π( m
2 πkT) 3 / 2
ν^2 e−mν(^2) / 2 kT
dv (4.7)
Fig. 4.1The Maxwell distribution
Flux
∅=
1
4
n<ν> (number of molecules striking unit area per second) (4.8)wherenis the number of molecules per unit volume.
Mean free path (M.F.P)
λ=1
√
2 πnσ^2(4.9)
wherenis the number of molecules per unit volume andσis the diameter of the
molecule.
Collision frequency
f=<ν>
λ(4.10)
Viscosity of gas (η)
η=1
3
ρλ<ν > (4.11)Thermal conductivity (K)
K=ηCν (4.12)whereCνis the specific heat at constant volume.