What is a key difference between alternating current (AC) and direct current (DC)?

The key difference between alternating current (AC) and direct current (DC) is that AC reverses direction periodically, while DC flows in a constant direction. This characteristic of AC allows it to change its voltage and frequency regularly, which is beneficial for various applications, including powering large machines and transmitting electricity over long distances.

In contrast, DC provides a steady voltage and current flow, making it suitable for electronic devices where consistent performance is needed. The ability of AC to easily change voltage levels using transformers makes it more efficient for electrical transmission over long distances, which is why AC is commonly used in residential and commercial power supply systems.

Understanding the nature of AC and DC is fundamental for those studying electrical systems, particularly in fields such as elevator design and maintenance, where both types of current might be utilized for different components.