Which statement best describes alternating current as opposed to direct current?

Which statement best describes alternating current as opposed to direct current?

• A. AC reverses direction periodically; DC flows in one direction
• B. DC reverses direction periodically; AC flows in one direction
• C. Both AC and DC reverse direction periodically
• D. Neither AC nor DC ever reverses direction

Answer: (A)

Alternating current reverses direction over time, while direct current flows in a single direction. The statement that alternating current reverses direction periodically while direct current flows in one direction fits this fundamental difference exactly. In practical terms, AC is what comes from wall outlets and typically follows a sinusoidal waveform, flipping polarity with every half-cycle. DC, like from batteries or many power supplies, maintains the same direction and polarity, delivering a steady voltage. The other descriptions don’t match how these currents behave: DC reversing periodically would not be true of a DC source, saying both reverse would imply both are AC, and saying neither reverses contradicts the defining nature of AC.

Alternating current reverses direction over time, while direct current flows in a single direction. The statement that alternating current reverses direction periodically while direct current flows in one direction fits this fundamental difference exactly. In practical terms, AC is what comes from wall outlets and typically follows a sinusoidal waveform, flipping polarity with every half-cycle. DC, like from batteries or many power supplies, maintains the same direction and polarity, delivering a steady voltage. The other descriptions don’t match how these currents behave: DC reversing periodically would not be true of a DC source, saying both reverse would imply both are AC, and saying neither reverses contradicts the defining nature of AC.