Thermodynamics - Result Question 29

30. If the ratio of specific heat of a gas at constant pressure to that at constant volume is γ, the change in internal energy of a mass of gas, when the volume changes from V to 2V at constant pressure P, is

[1998]

(a) R(γ1)

(b) PV

(c) PV(γ1)

(d) γPV(γ1)

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Answer:

Correct Answer: 30. (c)

Solution:

  1. (c) Change in internal energy is equal to work done in adiabatic system

ΔW=ΔU (Expansion in the system)

=1γ1(P1V1P2V2)

ΔU=11γ(P2V2P1V1)

Here, V1=V,V2=2V

ΔU=11γ[P×2VPV]=PV1γ

ΔU=PVγ1



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