Q115 / 160 · JIPMER 2005 · Physics

A monoatomic gas supplied the heat $Q$ very slowly keeping the pressure constant. The work done by the gas will be

  • Correct answer
    A
    $\frac{2}{3} Q$
  • B
    $\frac{3}{5} Q$
  • C
    $\frac{2}{5} Q$
  • D
    $\frac{1}{5} Q$

Solution

For monoatomic gas at constant pressure $\frac{\Delta U}{Q}=\frac{1}{3}$ or $\quad \Delta U=\frac{Q}{3}$ Now applying first law of thermodynamics $\begin{aligned} W & =\Delta Q-\Delta U \\ & =Q-\frac{Q}{3}=\frac{2 Q}{3}\end{aligned}$

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

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