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. The maximum emf occurs when the rate of flux change is greatest, which happens when the coil is perpendicular to the field ( sinθ = 1 ). Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v