Practice question

**Rotational emf** when coil area A rotates with angular speed ω in uniform field B, flux Φ = B A cos ωt, emf e = -N dΦ/dt = N B A ω sin ωt, maximum e₀ = N B A ω, frequency = ω/2π. For square side 22 cm area 0.0484 m² N=1 ω=14 rad/s B=0.15 T, e₀=1×0.15×0.0484×14=0.1016 V, sinusoidal. A = π r² = 3.14 × (0.07)² = 0.0154 m² . ε₀ = N B A ω = 180 × 0.07 × 0.0154 × 20 = 3.88 V ≈ 3.9 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N