Practice question

**Solenoid with magnetic core** produces field B = μ₀ μ_r n I inside, μ₀ = 4π×10⁻⁷ T·m/A, μ_r relative permeability, n = N/L turns per meter, I current. Core enhances field μ_r times, so given B, μ_r, n, current I = B/(μ₀ μ_r n) can be found, illustrating core effect on field strength. Magnetic intensity H = n I , where n is turns per unit length and I is current. Given: n = 500 m⁻¹ , I = 3 A . Substitute: H = 500 × 3 = 1500 A m⁻¹ . Substituting values gives 1500 A m⁻¹, which matches expected magnitude for this