Which statement best describes alternating current?

Which statement best describes alternating current?

• A. The current reverses direction periodically
• B. The current remains constant
• C. The current is always zero
• D. The current flows in a straight line

Answer: (A)

Alternating current is defined by the current changing direction periodically. In AC, the flow of charge reverses each half cycle, so the current rises and falls and switches direction over time. This is why the description that the current reverses direction periodically is the best choice. If the current remained constant, that would describe direct current, not alternating current. A current that is always zero isn’t correct because AC has nonzero values during each cycle, even though the average over a full cycle can be zero. The idea that the current flows in a straight line isn’t what distinguishes AC; the important feature is the periodic reversal of direction and the changing magnitude.

Alternating current is defined by the current changing direction periodically. In AC, the flow of charge reverses each half cycle, so the current rises and falls and switches direction over time. This is why the description that the current reverses direction periodically is the best choice. If the current remained constant, that would describe direct current, not alternating current. A current that is always zero isn’t correct because AC has nonzero values during each cycle, even though the average over a full cycle can be zero. The idea that the current flows in a straight line isn’t what distinguishes AC; the important feature is the periodic reversal of direction and the changing magnitude.