Practice question

Given: A solenoid with 1200 turns per meter and current 2.5 A has a core with μ_r = 200 . What is B inside? (Take μ_0 = 4π × 10⁻⁷T m A^{-1 ). These values define the system as per NCERT data. Formula: B = μ_0 μ_r n I. This is standard NCERT relation. Substitution & Calculation: Given: n = 1200 m^{-1, I = 2.5 A, μ_r = 200, μ_0 = 4π × 10⁻⁷. B = 4π × 10⁻⁷ × 200 × 1200 × 2.5 = 0.7536 T approx 0.75 T . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.