A tоrоidаl irоn core hаs: Meаn magnetic path length l = 0.5 m Cross-sectional area A = 5 × 10⁻⁴ m² Number of turns N = 200 Relative permeability μ_r = 1000 Permeability of free space μ₀ = 4π × 10⁻⁷ H/m Assume linear magnetic material, no air gap, and negligible leakage and fringing. Using I = 1 A, what is the magnetic flux Φ in the core?