A rod rotates at 18 rad/s in a 0.4 T field. If the length from the axis to the tip is 0.7 m, what is the emf induced?
**AC generator** principle same as rotating coil, N=200 turns A=0.04 m² B=0.1 T f=50 Hz ω=2π×50=314 rad/s, e₀= N B A ω =200×0.1×0.04×314=251.2 V, emf e= e₀ sin ωt, frequency equals rotation frequency, maximum when plane parallel to field. ε = (1/2) B ω R² . ε = (1/2) × 0.4 × 18 × (0.7)² = 1.764 V ≈ 1.76 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 U = ½ L I², result 1.76 V follows, reflecting Faraday's law and Lenz's opposition.
Ref: NCERT > Physics Book > Electromagnetic Induction > Rotational EMF and AC Generator
