Before revision: Therefore, AC voltage is often expressed as a root mean square (RMS) value, written as , because Power oscillation For this reason, AC power's waveform becomes Full-wave rectified sine, and its fundamental period is half of the one of the voltage's.
After revision: Therefore, AC voltage is often expressed as a root mean square (RMS) value, written as , because Power oscillation For this reason, AC power's waveform becomes Full-wave rectified sine, and its fundamental frequency is double of the one of the voltage's.