Practice question

**Solenoid carries steady current** second coil experiences emf only when current in solenoid changes because dΦ/dt ≠0 only when I changes, steady current gives constant flux, no induction, illustrating Faraday's law requires changing flux, not static field. ε = N (Δ Φ/Δ t) . Δ Φ = 0.01 Wb , Δ t = 0.05 s , N = 40 . ε = 40 × (0.01/0.05) = 40 × 0.2 = 8 V . 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