During which portion of an AC cycle does the current reach its peak value?

The peak value of current in an AC cycle occurs at the 90° and 270° points due to the sinusoidal nature of alternating current. In a standard AC waveform, the current starts at zero and rises to its maximum positive value at 90°. This is where the current waveform crosses the horizontal axis moving towards its peak. Similarly, at 270°, the current reaches its maximum negative value, marking another point of peak magnitude despite being negative.

Understanding the position of these peak points within the cycle is critical, especially in applications such as power calculations, where knowing the maximum current can influence overall system design and efficiency.

Other options reference situations that do not align with the peak current occurrence. The zero crossing points occur at 0° and 180°, where the current is actually zero. Maximum frequency does not directly relate to the peak current, as frequency represents the number of cycles per second rather than the instantaneous values within a cycle. Phase shift junctions, while influencing the timing of waveforms, do not correspond directly to the moments of peak current; these junctions are more about the relationship between different AC waveforms rather than defining peak values within a single waveform.