AC (alternating current) is a type of electrical current that periodically reverses direction. Unlike DC (direct current), which flows in a single direction, AC changes its flow direction many times per second. This characteristic makes AC suitable for powering homes and businesses, as it can be easily transformed to different voltages. AC is generated by power plants and transmitted over long distances through power lines. The frequency of AC is measured in hertz (Hz), indicating how many times the current changes direction in one second. In most countries, the standard frequency is either 50 Hz or 60 Hz.