Calculate inductance for solenoids, toroids, and coaxial cables
Solenoid: L = μ₀μᵣN²A/l
Toroid: L = μ₀μᵣN²h × ln(r₂/r₁) / (2π)
Coaxial: L/l = μ₀ × ln(r₂/r₁) / (2π)