SSC JE Mechanical Engineering 11 Oct 2020 Shift 1 Papers

Question : 146 of 200

Marks: +1, -0

A diatomic gas is enclosed in a piston-cylinder arrangement at a pressure of 3 bar and 300 K. The cylinder has a volume of 1.5

m^{3}

. The process undergoes isothermal expansion to 3

m^{3}

. If the gas has a gas-constant as 1.486 KJ/Kg. using, In2 = 0.693, entropy change during the above process in kJ/kg is:

Solution:

Given:

{R}=1.486 {KJ} \/ {Kg}, {V}_{1}=1.5 {m}^{3}

\;\; {V}_{2}=3 {m}^{3}

{s}_{2}-{s}_{1}={R} \ln ({{V}_{2}}/{{V}_{1}}\)

{s}_{2}-{s}_{1}=1.486 \ln ({3}/{1.5})

{s}_{2}-{s}_{1}=1.03

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