It's AC and the cycle (Hz) is x, then the voltage hits +/- max at 2x and also crosses 0 at 2x. Current in the system also crosses 0 at 2x although the phase ang

It's AC and the cycle (Hz) is x, then the voltage hits +/- max at 2x and also crosses 0 at 2x. Current in the system also crosses 0 at 2x although the phase angle is likely to differ from the applied voltage.