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MHT CET · Physics · Thermodynamics

A monoatomic ideal gas, initially at temperature ' \(\mathrm{T}_1\) ' is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature ' \(\mathrm{T}_2\) ' by releasing the piston suddenly \(L_1\) and \(L_2\) are the lengths of the gas columns before and after the expansion respectively. The \(\frac{T_2}{T_1}\) is

  1. A \(\left[\frac{\mathrm{L}_1}{\mathrm{~L}_2}\right]^{2 / 3}\)
  2. B \(\left[\frac{\mathrm{L}_1}{\mathrm{~L}_2}\right]^{1 / 2}\)
  3. C \(\left[\frac{\mathrm{L}_2}{\mathrm{~L}_1}\right]^{1 / 2}\)
  4. D \(\left[\frac{\mathrm{L}_2}{\mathrm{~L}_1}\right]^{2 / 3}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\left[\frac{\mathrm{L}_1}{\mathrm{~L}_2}\right]^{2 / 3}\)

Step-by-step Solution

Detailed explanation

In an adiabatic process \(\mathrm{T}_1 \mathrm{~V}_1^{\gamma-1}=\mathrm{T}_2 \mathrm{~V}_2^{\gamma-1}\)
For an ideal mono atomic gas the no of degree of freedom is 3
\(Y=1+\frac{2}{f}=1+\frac{2}{3}\)
\(\frac{\mathrm{T}_1}{\mathrm{~T}_2}=\left(\frac{\mathrm{V}_2}{\mathrm{~V}_1}\right)^{\mathrm{Y}-1}=\left(\frac{\mathrm{V}_2}{\mathrm{~V}_1}\right)^{2 / 3}=\left(\frac{\mathrm{L}_2}{\mathrm{~L}_1}\right)^{2 / 3}\)
Since volume is proportional to length due to area being constant.