How often does alternating current change polarity?

Alternating current (AC) changes polarity based on its frequency, which indicates how many cycles it completes in one second. In the context of common household and commercial AC power, the standard frequency in the United States is 60 Hz, which means the current changes polarity 60 times each second. This corresponds to each cycle of the waveform, where the current flows in one direction for half of the cycle, and in the opposite direction for the other half.

This frequency is a crucial aspect of AC power systems, affecting how electrical devices operate. In other regions, such as Europe, a frequency of 50 Hz is common, leading to a different number of polarity changes per second.