Practice question

Given: A solenoid produces B = 0.75 T with a core of μ_r = 500 and n = 1000 m^{-1 . What is the current I ? (Take μ_0 = 4π × 10⁻⁷ T m A^{-1 ). These values define the system as per NCERT data. Formula: B = μ_0 μ_r n I, so I = B/μ_0 μ_r n. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Given: B = 0.75 T, μ_r = 500, n = 1000 m^{-1, μ_0 = 4π × 10⁻⁷. I = frac0.754π × 10⁻⁷ × 500 × 1000 = frac0.756.283 × 10⁻¹ approx 1.194 A approx 1.2 A . 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.