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

The primary distinction between alternating current (AC) and direct current (DC) lies in the nature of their flow. In AC, the electric charge periodically reverses direction, which means the current changes flow back and forth at regular intervals. This characteristic is due to the way AC is generated, typically by rotating machinery that produces a sine wave pattern, allowing it to be transformed to different voltage levels easily.

In contrast, DC flows consistently in a single direction. This unidirectional flow results from the power sources, such as batteries or solar cells, where the electron flow remains constant and does not alternate. Understanding this fundamental difference helps in grasping how AC is commonly utilized for powering homes and businesses, while DC finds its applications in electronics and devices that require a stable voltage.

The other choices touch on aspects of AC and DC but do not accurately state their fundamental difference. For instance, residential wiring primarily utilizes AC due to its ability to transmit electricity over long distances efficiently, while DC is prevalent in low-voltage applications. Similarly, while AC can have a variable voltage in specific cases (like is seen with transformers), it typically operates within a fixed range in residential setups.