What is the primary difference between alternating current (AC) and direct current (DC)?

The primary difference between alternating current (AC) and direct current (DC) lies in the direction of flow of the electric charge. In AC, the flow of electric charge changes direction periodically. This means that the voltage level alternates as time progresses, typically following a sine wave pattern. This characteristic allows AC to be transmitted over long distances more efficiently, making it suitable for power grids and household electricity.

In contrast, DC flows in a single direction, maintaining a constant voltage. This type of current is commonly used in batteries, electronic devices, and other applications where a stable and unidirectional flow of electricity is necessary. The distinction in current directionality is crucial in understanding how various electrical systems and devices operate.

The other options do not accurately represent the fundamental differences. For instance, suggesting that AC has a higher voltage than DC can be misleading, as both types of current can operate at varying voltage levels depending on the application. Similarly, the statement about AC being used for batteries contradicts the standard understanding of how AC and DC are employed in real-world applications.