What is a defining characteristic of alternating current?

A defining characteristic of alternating current (AC) is that it changes polarity 60 times per second, which corresponds to its frequency of 60 Hertz (Hz) in many power systems, particularly those in the United States. This means that in one second, the current alternates its direction of flow and effectively changes its voltage from positive to negative and back again 60 times.

This alternating nature is essential for the functioning of many electrical systems and appliances, as it allows for the efficient transmission of electricity over longer distances compared to direct current (DC). The frequency of the AC supply determines how often this change occurs, which is why knowing that it switches 60 times per second is crucial for understanding how AC operates in practice. It allows for compatibility with transformers and other devices that are designed to work with alternating current, enabling efficient energy distribution.