NLC Electric Systems Practice Exam 2025 – Complete Test Prep

The distinction that AC changes direction periodically while DC flows in one direction is fundamental to understanding these two types of electrical current.

Alternating current (AC) is characterized by its oscillation; it reverses direction at regular intervals, typically measured in hertz (Hz). This property allows AC to effectively transmit power over long distances, making it the preferred choice for power grids and household electricity supply. The ability of AC to change direction enables transformers to increase or decrease voltage levels efficiently, which is crucial for the distribution of electric power.

On the other hand, direct current (DC) flows consistently in a single direction. This steady flow makes DC suitable for low-voltage applications, such as batteries, electronic devices, and renewable energy systems, where a stable voltage is required.

Understanding these differences is key to grasping how electricity is utilized in various applications and systems.