How many times per second does AC alternate between DC positive and DC negative?

The correct answer highlights that Alternating Current (AC) in North America typically alternates 60 times per second, which corresponds to a frequency of 60 Hertz (Hz). This means that in one complete cycle, the voltage changes from positive to negative and back to positive again, completing these changes 60 times each second.

Understanding that AC’s frequency is determined by the electrical power standards in different regions is crucial. In the United States and Canada, the standard frequency is set at 60 Hz, which is why this is the correct choice. This frequency ensures that electrical devices operate efficiently and consistently, leveraging the properties of AC for various applications, including in welding processes where AC is often preferred for the stability it provides during welding operations.

In contrast, other frequencies such as 50 Hz are commonly found in other parts of the world, including Europe, which is lower than the American standard. Therefore, while there are differences in global standards for frequency, in the context of this question, 60 times per second is the benchmark for AC systems in North America.