What is the difference between AC and DC current?

The distinction between AC (Alternating Current) and DC (Direct Current) is fundamentally based on the direction of the flow of electric charge. AC current alternates in direction, meaning that the flow of electrons periodically changes from one direction to the opposite direction. This is characteristic of electrical power systems, where the voltage level alternates typically in a sinusoidal manner over time.

In contrast, DC current flows in one direction only. This means that the electrons move steadily from the negative terminal to the positive terminal, which is the mode of operation for batteries and many electronic devices. Understanding this difference is crucial because it impacts how electrical energy is generated, transmitted, and utilized in different applications.

The other choices do not accurately capture the fundamental nature of AC and DC current. For example, while AC is indeed used primarily in power grids, DC is not exclusive to batteries. Furthermore, although AC systems are efficient for long-distance transmission, the statement about voltage does not highlight the essential difference between the two types of current. Recognizing that AC alternates direction while DC flows unidirectionally is key to understanding how they function in various electrical systems and applications.