Practice question

Given: A bar magnet produces a field of 2 × 10⁻⁶ T at 0.5 m on its equatorial line. What is its magnetic moment? (Take μ_0 = 4π × 10⁻⁷ T m A^{-1 ). These values define the system as per NCERT data. Formula: B = μ_0/4π m/r³, so m = fracB r³μ_0/4π. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Given: B = 2 × 10⁻⁶ T, r = 0.5 m, μ_0/4π = 10⁻⁷. m = frac2 × 10⁻⁶ × (0.5)³¹⁰⁻⁷= frac2 × 10⁻⁶ × 0.12510⁻⁷= 2.5 A m² . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.