when looking at a sine wave in AC voltage, a cycle is represented by ___________.

• A. One positive and one negative alteration
• B. A peak
• C. A trough
• D. A zero crossing

Answer: (A)

AC voltage swings above and below zero in a smooth, continuous wave. One full cycle means the wave has completed both a positive half and a negative half, returning to its starting phase. In other words, it includes one positive alteration and one negative alteration, fully tracing from zero up to the positive peak, back through zero to the negative peak, and back to zero. A peak or a trough alone is only half of that complete swing, and a zero crossing is just a point within the cycle. So the full cycle is the combined positive and negative alternations of the sine wave.