What does Alternating Current (AC) refer to?

Alternating Current (AC) refers to the type of electric current that changes direction periodically, which is accurately represented by the idea of current flowing in two directions. This characteristic enables AC to be more efficient for transmitting electricity over long distances because it can easily be transformed to different voltage levels, optimizing energy distribution. In practical applications, AC is used in most household electricity and is generated by power plants, whereas Direct Current (DC) flows in a single direction and does not fluctuate.

This alternating nature of AC is fundamental to its application in electrical systems, as it allows for the use of transformers to step voltage up or down as needed. Other options fail to accurately describe AC; for instance, the flow of current in one direction pertains to DC, while stable current with no fluctuation inaccurately describes AC, which is defined by its periodic changes.