Alternating Current (AC) is an electric current that reverses direction periodically, contrasting with Direct Current (DC), which flows in a single direction. AC is the form of electrical energy commonly used in homes and businesses, allowing for efficient transmission over long distances due to its ability to be transformed to higher voltages. The frequency of AC is measured in hertz (Hz), indicating how many times the current changes direction per second. In most countries, the standard frequency is either 50 Hz or 60 Hz. AC is essential for powering a wide range of devices, from household appliances to industrial machinery.