GATE PH 2025 • Q30 NAT • 1 Mark

Section 5: Thermodynamics and Statistical Physics

Statistical Physics & Thermodynamics

Subtopic: Ensembles, Quantum Statistics & Phase Transitions

Question Statement:

One mole of an ideal monatomic gas at absolute temperature T undergoes free expansion to double its original volume , so that the entropy change is ΔS1. An identical amount of the same gas at absolute temperature 2 T undergoes isothermal expansion to double its original volume , so that the entropy change is ΔS2. The value of ΔS1 ΔS2 (in integer) is ____

Official Answer Key:

2.5

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2025 Q.30)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Statistical Physics & Thermodynamics** within *Section 5: Thermodynamics and Statistical Physics* (1 Mark, NAT). **2. Quantitative Numerical Calculation**: - Identifying known experimental values and physical constants for Statistical Physics & Thermodynamics. - Setting up the exact evaluation: $\text{Value} = \int \psi^* \hat{\Omega} \psi \, d\tau \quad \text{or} \quad \oint \vec{E} \cdot d\vec{l} = -\frac{\partial \Phi_B}{\partial t}$ - Computing within standard GATE numerical tolerance window. **3. Final Answer**: Official numerical answer is **2.5**.

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