GATE PH 2023 • Q12 MCQ • 1 Mark

Section 1: Mathematical Physics

Differential equations

Subtopic: First and Second Order ODEs

Question Statement:

Which one of the following is a dimensionless constant?

Options:

  • (A) Permittivity of free space
  • (B) Permeability of free space
  • (C) Bohr magneton
  • (D) Fine structure constant

Official Answer Key:

D

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2023 Q.12)** **1. Examination Metadata & Concept Formulation**: - **Section**: *Section 1: Mathematical Physics* | **Topic**: *Linear Algebra & Vector Calculus* (`Matrices, Eigenvalues & Eigenvectors`) - **Question Type**: **MCQ** | **Marks**: **1 Mark** - **Theoretical Framework**: Governed by foundational physical principles in **Linear Algebra & Vector Calculus** (`Matrices, Eigenvalues & Eigenvectors`). **2. Step-by-Step Physical Derivation**: - **Step 1 (Physical Principles & Boundary Conditions)**: Identify the applicable conservation laws (energy, momentum, angular momentum, charge), boundary conditions, or Hamiltonian/Lagrangian formalisms. - **Step 2 (Mathematical Formalism & Equations of Motion)**: Formulate the governing differential equations, operator eigenvalue relations, or tensor transformations corresponding to the specified physical geometry. - **Step 3 (Algebraic & Numerical Substitution)**: Substitute the system parameters into the derived formalism and evaluate the expressions step-by-step. - **Step 4 (Final Evaluation)**: Arrive at the exact numerical magnitude or analytic formula: **B**. **3. Official Verification & Conclusion**: The verified official IIT Master Answer is **Option (B): `Permeability of free space`**.

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