MCQEasyJEE 2023Equation of State of Ideal Gas

JEE Physics 2023 Question with Solution

The correct relation between γ=CpCv\gamma = \frac{C_p}{C_v} and temperature TT is:

  • A

    γ1T\gamma \propto \frac{1}{\sqrt{T}}

  • B

    γT0\gamma \propto T^0

  • C

    γ1T\gamma \propto \frac{1}{T}

  • D

    γT\gamma \propto T

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: The relation between γ=CpCv\gamma = \frac{C_p}{C_v} and temperature TT is asked.

Find: Which option correctly describes how γ\gamma depends on TT.

For an ideal gas, the specific heat ratio γ\gamma is independent of temperature over the usual range considered here. Therefore, γ\gamma remains constant with change in TT.

This is written as:

γT0\gamma \propto T^0

Hence, the correct relation is γT0\gamma \propto T^0.

The solution states option A, but that is inconsistent with the listed options and with the written conclusion. The defensible correct option from the provided options is B.

Common mistakes

  • Assuming that γ\gamma varies directly with temperature. This is incorrect for the ideal-gas treatment used here. Instead, identify that γ=CpCv\gamma = \frac{C_p}{C_v} is taken as approximately constant.

  • Reading the option label from the solution without checking the actual expression. The solution text says option A, but the expression written is γT0\gamma \propto T^0, which matches option B in the given list. Always match the formula, not only the label.

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