Practice question

**Energy in inductor** cannot change instantaneously because that would require infinite power, current through inductor continuous, voltage may jump, principle used in chokes, inductive kick, back emf, explaining why inductor opposes change in current. W = (1/2) L I² = (1/2) × 0.4 × (7)² = 0.2 × 49 = 9.8 J . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt) and U = ½ L I², result 9.8 J follows, reflecting Faraday's law and Lenz's opposition.