Electrician's Licensing Practice Exam

What is a key difference between AC and DC electricity?

1. AC maintains a constant flow, while DC varies

2. DC flows in one direction, while AC alternates

3. AC is used in batteries, while DC powers homes

4. DC can only be generated from solar power

The correct answer is: DC flows in one direction, while AC alternates

The distinction that DC flows in one direction while AC alternates is fundamental to understanding the characteristics of these two types of electricity. Direct Current (DC) means that electrons flow steadily in a single direction, which is typical in battery-operated devices. On the other hand, Alternating Current (AC) changes its direction periodically, which is the standard for electrical outlets in homes and businesses, allowing efficient transmission of electricity over long distances. This alternating nature of AC is what makes it suitable for power distribution grids, as it can easily be transformed to different voltage levels, making it more versatile for varying applications in homes and industries. Recognizing this difference is critical for electricians, as it affects how circuits are developed, how appliances are powered, and how electrical safety is managed. Understanding that AC does not maintain a constant flow is also key, as it inherently fluctuates between positive and negative values. This helps underline why AC is predominantly used for power grids and in large-scale transmission systems, differentiating it from the stable, unidirectional flow of DC. The other choices present misconceptions about the use and generation of AC and DC electricity and do not accurately describe this fundamental difference.