Which statement best describes the difference between AC and DC current?

The correct statement highlights the fundamental characteristics of alternating current (AC) and direct current (DC). AC is defined by its ability to change direction periodically, meaning that the current flows in one direction for a certain period of time and then switches to flow in the opposite direction. This characteristic allows AC to be easily transformed between voltages using transformers, making it highly suitable for long-distance power transmission.

In contrast, DC flows continuously in a single direction. This means that the current maintains a consistent polarity and does not alternate. DC is commonly generated by sources such as batteries and solar panels, and while it is used for many electronic devices and applications, it is less efficient for transmitting power over long distances compared to AC.

Understanding the nature of AC and DC is critical in electrical engineering, as it informs decisions regarding the design and use of electrical systems, particularly in applications like power distribution and electronics. The other statements misrepresent these fundamental characteristics, thus reinforcing the correctness of the chosen response.