An alternating current (AC) generator, or alternator, converts mechanical rotational energy into sinusoidal electrical energy via Faraday's law of electromagnetic induction. As an armature coil rotates at constant angular frequency ω within a stationary uniform magnetic field established by stator poles, the effective cross-sectional area intercepting magnetic flux lines varies harmonically as a function of angle θ = ωt. This continuous variation in magnetic flux induces an alternating electromotive force that reverses polarity twice per mechanical revolution.