Question

In a throttling process, the pressure of an ideal gas reduces by 50%. If C_p­ and C_v are the heat capacities at constant pressure and constant volume respectively (γ = C_p/C_v), the specific volume will change by a factor of
1. 2^{1/ γ} 
2. 2^{(γ -1)/ γ}
3. 0.5
4. 2

Answer 1

Correct Answer - Option 4 : 2

Enthalpy h = u + pv

For throttling process, enthalpy remains constant and for an ideal gas in throttling temperature remains constant.

⇒ u₁ + P₁V₁ = u₂ + P₂V₂

As for ideal gas u = f(T)

⇒ u₁ = u₂ as T₁ = T₂

∴ P₁V₁ = P₂V₂

Now, \(\frac{{{V_2}}}{{{V_1}}} = \frac{{{P_1}}}{{{P_2}}} = \frac{{{P_1}}}{{0.5\;{P_1}}} = 2\)