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JEE Main 2023 (31 Jan, Shift 2) · Thermodynamic Processes

Thermodynamic Processes question from JEE Main 2023 (31 Jan, Shift 2)

Q155JEE Main 2023 · 31 JAN · SHIFT 2Medium

Thermodynamic Processes

A hypothetical gas expands adiabatically such that its volume changes from 8 litres to 27 litres. If the ratio of final pressure of the gas to initial pressure of the gas is 1681\frac{16}{81}. Then the ratio of CpCv\frac{C_p}{C_v} will be.

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Answer: (b)

  1. Adiabatic: PVγ=PV^{\gamma} = const, so P2P1=(V1V2)γ\frac{P_2}{P_1} = \left(\frac{V_1}{V_2}\right)^{\gamma}.
  2. 1681=(827)γ=(23)3γ\frac{16}{81} = \left(\frac{8}{27}\right)^{\gamma} = \left(\frac{2}{3}\right)^{3\gamma} and 1681=(23)4\frac{16}{81} = \left(\frac{2}{3}\right)^{4}.
  3. 3γ=4⇒γ=433\gamma = 4 \Rightarrow \gamma = \frac{4}{3}
  4. So the answer is (b) 43\frac{4}{3}.
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