Practice question

Given: A bar magnet with m = 1.4 A m² produces a field at 0.4 m on its equatorial line. What is B ? (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. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Given: m = 1.4 A m², r = 0.4 m, μ_0/4π = 10⁻⁷. B = 10⁻⁷ × 1.4/(0.4)³ = 10⁻⁷ × 1.4/0.064 approx 2.1875 × 10⁻⁶ T approx 2.19 × 10⁻⁶ T . 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.