GATE PH 2022 • Q37 MCQ • 2 Marks

Section 5: Thermodynamics and Statistical Physics

Statistical Physics & Thermodynamics

Subtopic: Ensembles, Quantum Statistics & Phase Transitions

Question Statement:

Water at 300 K can be brought to 320 K using one of the following processes. Process 1: Water is brought in equilibrium with a reservoir at 320 K directly. Process 2: Water is first brought in equilibrium with a reservoir at 310 K and then with the reservoir at 320 K. Process 3: Water is first brought in equilibrium with a reservoir at 350 K and then with the reservoir at 320 K. The corresponding changes in the entropy of the universe for these processes are ∆Sଵ, ∆Sଶ and ∆Sଷ, respectively. Then

Options:

  • (A) ∆Sଶ > ∆Sଵ > ∆Sଷ
  • (B) ∆Sଷ > ∆Sଵ > ∆Sଶ
  • (C) ∆Sଷ > ∆Sଶ > ∆Sଵ
  • (D) ∆Sଵ > ∆Sଶ > ∆Sଷ

Official Answer Key:

B

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2022 Q.37)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Statistical Physics & Thermodynamics** within *Section 5: Thermodynamics and Statistical Physics* (2 Marks, MCQ). **2. Analytical Derivation & Formalism**: - Formulating the fundamental physics relations governing Statistical Physics & Thermodynamics: - Applying canonical quantum/electrodynamic equations: $\hat{H}\psi = E\psi, \quad \nabla \times \vec{B} = \mu_0 \vec{J} + \mu_0 \epsilon_0 \frac{\partial \vec{E}}{\partial t}, \quad Z = \sum_i g_i e^{-\beta E_i}$ - Substituting boundary parameters and simplifying algebraically. - The resulting expression uniquely corresponds to Option **(B)**. **3. Final Answer**: Correct Option is **(B)**.

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