An a.c. generator is a rectangular coil that spins in a uniform magnetic field. When the coil spins the flux linkage changes continuously. The flux linkage is given by NΦ = BANcosθ where θ is the angle between the normal to the plane of the coil and the magnetic field. If the coil spins at frequency f then θ = 2πft.According to Faraday's Law, the induced emf is equal to the rate of change of magnetic flux linkage. So the alternating emf is given byε = ε0sin 2 πft
where the peak emf ε0 = BANω = 2πfBAN.
where the peak emf ε0 = BANω = 2πfBAN.