What is the key difference between AC and DC currents?

The key difference between AC (Alternating Current) and DC (Direct Current) lies in how the current flows. In AC, the flow of electrical charge changes direction periodically, resulting in the current and voltage oscillating between positive and negative values. This characteristic allows AC to be easily transformed to different voltage levels using transformers, making it highly suitable for long-distance power transmission and typical in residential and commercial power systems.

In contrast, DC maintains a constant flow of electrical charge in one direction, making it stable and predictable. This constancy is advantageous for certain applications such as batteries, electronics, and devices that require a uniform voltage.

The other options do not capture the essence of this fundamental difference. While it is true that AC is commonly used in residential wiring, and that DC has specific applications, these points do not directly address the core aspect of how the currents behave. Therefore, understanding the periodic nature of AC compared to the constant flow of DC is essential for grasping the basic principles of electrical currents.