How does AC differ from DC current?

AC, or alternating current, is characterized by its ability to change direction periodically, typically in a sinusoidal waveform. This means that the flow of electrons alternates, reversing direction at regular intervals, which is commonly observed in power systems that supply electricity to homes and businesses. The frequency of this alternating cycle can vary, with common values being 50 Hz in Europe and 60 Hz in the United States.

On the other hand, DC, or direct current, flows in a constant direction. It provides a steady voltage and current, making it useful for devices that require a stable power supply, such as batteries, electronics, and some smaller appliances. The fundamental difference lies in the behavior of the current: AC's periodic reversal of direction compared to DC's unidirectional flow.

The other options allude to related concepts. While it's true that AC can be stepped up or down to higher or lower voltages using transformers—often making it more suitable for long-distance transmission—the claim that DC is primarily used in household outlets misrepresents the common practice, as most household outlets provide AC power. Thus, the distinctive nature of AC changing direction periodically while DC maintains a constant flow accurately captures the essence of their differences.