Practice question

**Energy stored in inductor** U =½ L I², L inductance, I current, energy in magnetic field, density u = B²/(2μ₀), B=μ₀ n I inside solenoid, U = (B²/2μ₀)×volume, illustrating equivalence of circuit and field energy. L = μ₀ n² A l , assume l = 1 m . L = 4π × 10⁻⁷ × (600)² × 0.012 × 1 = 0.00543 H . ε = L (Δ I/Δ t) = 0.00543 × (1 - 4/0.2) = 0.00543 × (-15) = 0.08145 V ≈ 0.081 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v =