Alternating current is defined as which of the following?

• A. A continuous flow that rhythmically changes direction, alternating from positive to negative
• B. A steady unidirectional flow from anode to cathode
• C. Static electrical charge stored on insulators
• D. A direct current used in batteries

Answer: (A)

Alternating current is a flow of electric charge that periodically reverses direction. It continually switches between positive and negative directions, rather than moving in one fixed direction. In most systems the reversal follows a repeating waveform, typically a smooth sine wave, which makes voltage and current easy to transform and distribute. This is different from direct current, which flows steadily in one direction. Static charge on insulators describes electrostatics, not a current, and batteries provide direct current. So the description that matches alternating current is the one where the flow rhythmically changes direction, alternating from positive to negative.