How frequently does alternating current change its polarity?

Alternating current (AC) changes its polarity in a manner that is notably related to its frequency. In most standard electrical systems, particularly in the United States, the frequency of AC is commonly set at 60 hertz (Hz). This means that the current not only alternates direction once for every cycle but does so twice per cycle: once for positive polarity and once for negative polarity. Consequently, the correct answer—60 times per second—indicates that the polarity changes occur consistently at this frequency, making it standard in many applications including household and commercial electrical systems.

This understanding is essential for anyone working with electrical systems or equipment that operates on AC, as it affects the design and compatibility of devices, motors, and other electrical components.