Q95 / 180 · AIIMS 2017 · Physics

When an ideal monoatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is

  • A
    $2 / 5$
  • Correct answer
    B
    $3 / 5$
  • C
    $3 / 7$
  • D
    $5 / 7$

Solution

By first law of thermodynamics $Q=U+W$ $\begin{aligned} & \quad=\frac{f}{2} n R T+P \int d V=\frac{f}{2} n R T+P V \\ & \text { or } \quad Q=\frac{f}{2} n R T+n R T \quad(\because P V=n R T)\end{aligned}$ $=\frac{3}{2} n R T+n R T=\frac{5}{2} n R T$ Fraction of heat energy supplied $=\frac{U}{Q}$ $=\frac{(3 / 2) n R T}{(5 / 2) n R T}=\frac{3}{5}$

Hence, the correct answer is option: 'B'.

More Thermodynamics Questions