This document discusses sinusoidal voltage and current, providing definitions and comparisons between alternating current (AC) and direct current (DC). It defines that sinusoidal or alternating current changes direction every half cycle, while direct current does not change direction. The document also discusses terms used to describe sinusoidal waves like amplitude, instantaneous value, time period, and frequency. It provides diagrams of sinusoidal current over angle and time. Methods for generating AC through a moving magnetic field or conductor are also presented, as well as advantages of using AC in homes and appliances.