What type of current flows first in one direction and then in the opposite direction?

The correct choice involves the type of current that alternates its flow direction. Alternating Current (AC) is defined by its characteristic behavior of changing direction periodically. This means that the electrical flow first travels in one direction and then reverses, flowing in the opposite direction. This oscillation occurs at a specific frequency, commonly measured in hertz (Hz), which indicates how many times the current changes direction in one second.

In contrast, Direct Current (DC) flows consistently in a single direction, making it unsuitable for this definition. Pulsating Current, while it may seem similar due to its variability, typically refers to currents that not only change direction but also fluctuate in magnitude within the same direction, rather than reversing like AC. Residual Current refers to leakages that can occur in electrical systems and is not characterized by directional flow.

Understanding the nature of these currents is essential for safe practices and effective use of electrical systems in esthetics and beyond.