NEET 2022 Physics Adiabatic Processes MCQ Question

Chapter: Thermodynamics

Class: 11 Physics Topic: P–V Diagram: Thermodynamic Processes Difficulty: 🟡 Moderate

✅ Ans: D — 2

From the same initial state:

• 1 → Isochoric: Volume constant → vertical line.
• 4 → Isobaric: Pressure constant → horizontal line.
• 2 → Adiabatic: $PV^\gamma=\text{constant}$
• 3 → Isothermal: $PV=\text{constant}$

For expansion from the same initial state:

$$\text{Adiabatic curve falls faster than isothermal}$$

because

$$\left(\frac{dP}{dV}\right)_{\text{adiabatic}} =-\gamma\frac{P}{V}$$

and

$$\left(\frac{dP}{dV}\right)_{\text{isothermal}} =-\frac{P}{V}$$

Since $\gamma>1$, curve 2 is steeper and lies below curve 3.

🧠 NEET Trick

Expansion: Adiabatic → steeper → pressure falls faster. So 2 = Adiabatic.

Correct answer: D (2).