Which statement best defines alternating current (AC)?

Which statement best defines alternating current (AC)?

• A. Changes in amplitude and reverses direction at regular intervals
• B. Flows in one direction only
• C. Is a potential difference measured in volts
• D. Is the rate of electron flow

Answer: (A)

Alternating current is current that changes direction periodically, with its magnitude rising and falling in a repeating pattern. The key feature is that the sign of the current reverses every half cycle, so it flows first in one direction and then in the opposite direction. This alternating nature is what produces the familiar wave-like current and voltage in power systems, with mains power typically reversing at 50 or 60 Hz. Direct current, by contrast, flows in one direction with roughly constant magnitude. Describing it as a potential difference in volts refers to voltage rather than current, and describing it as the rate of electron flow is a general way to talk about current but doesn’t specify that it alternates.

Alternating current is current that changes direction periodically, with its magnitude rising and falling in a repeating pattern. The key feature is that the sign of the current reverses every half cycle, so it flows first in one direction and then in the opposite direction. This alternating nature is what produces the familiar wave-like current and voltage in power systems, with mains power typically reversing at 50 or 60 Hz. Direct current, by contrast, flows in one direction with roughly constant magnitude. Describing it as a potential difference in volts refers to voltage rather than current, and describing it as the rate of electron flow is a general way to talk about current but doesn’t specify that it alternates.