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Thermodynamics

Question
CBSEENPH11026314

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of absolute temperature. The ratio CPCV for the gas is

  • 43

  • 2

  • 53

  • 32

Solution

D.

32

Given, that

           ρ  T3

⇒     ρ T -3 = constant         .....(i)

Also for adiabatic process,

       ρ V γ = Constant

But  pV = RT (ideal gas law)

 ⇒    V = RTρ

∴     ρRTργ = constant  

      ρ1-γ Tγ = constant             ..... (ii)

⇒     ρ Tγ1-γ = constant 

Equating Eqs. (i) and (ii), we get

    γ1 - γ = -3

⇒     γ = -3 + 3γ

⇒    2γ = 3

⇒     γ = 32

⇒     CPCV = 32