At what level does voltage begin for each sine wave in alternating current (AC)?

The starting point for each sine wave in alternating current (AC) is the zero level. In AC systems, the voltage oscillates between positive and negative peaks in a smooth sinusoidal cycle. At the zero point, the voltage crosses the axis, transitioning from negative to positive values. This zero crossing is significant because it is when the voltage changes direction and represents the neutral point in the sine wave cycle.

In the context of AC systems, understanding where the wave begins is crucial for correct measurements and analysis of electrical systems, as it impacts the calculation of root mean square (RMS) values, frequency, and phase relationships. This foundational knowledge is important for various applications in electrical engineering and IT systems, aligning with the principles outlined in the BICSI IT Systems Installation Methods Manual.