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GATE 2026 CH – Question 15

Thermodynamics · Laws of thermodynamics, open and closed systems, entropy and chemical potential · 1 mark · Multiple choice

Consider a closed system of one mole of an ideal gas undergoing a polytropic process. The process follows $PV^n = $ constant, where P is the pressure, V is the volume and n is a constant. If the process is isobaric, which one of the following is the value of n?

  1. 0
  2. 1
  3. $\infty$
  4. the ratio of specific heat capacity at constant pressure to specific heat capacity at constant volume

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Correct answer: (A) 0

Explanation

For an isobaric process $P$ is constant, so $PV^n = $ constant holds only if $V^n$ does not change with $V$, that is $n = 0$. Here $n = 1$ is isothermal, $n = \gamma$ is adiabatic and $n = \infty$ is isochoric.