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

The main difference between direct current (DC) and alternating current (AC) lies in the direction of the flow of electrons. In a DC circuit, the current flows in a constant direction, meaning the electrons move from the negative terminal to the positive terminal of the power source. This unidirectional flow is characteristic of batteries and many electronic devices that use steady voltage levels.

On the other hand, AC current changes direction periodically. This means that the voltage alternates, typically in a sinusoidal pattern, causing the electrons to flow first in one direction and then in the opposite direction. This is commonly used in household power supplies and various electrical devices due to its efficiency in transmission over long distances.

The correct choice highlights that DC maintains a single flow direction, while AC shifts direction at regular intervals, which impacts how each type of current is applied in practical electrical systems.