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. B = μ₀ μ_r n I , so I = (B/μ₀ μ_r n) . Given: B = 0.96 T , μ_r = 300 , n = 1000 m⁻¹ , μ₀ = 4π × 10⁻⁷ . I = (0.96/4π × 10⁻⁷ × 300 × 1000) = (0.96/3.769 × 10⁻¹) ≈ 2.548 A ≈