Video narration
What does the familiar 230-volt rating on a wall socket actually mean, if the voltage keeps changing? With alternating current, or AC, voltage rises, falls to zero, then reverses polarity. A sine wave repeats this pattern, so its instantaneous value keeps changing. The peak value is its highest voltage. But a 230-volt rating isn't the peak. The RMS value tells you the steady DC voltage that produces the same heating in the same resistor. For a sinusoidal voltage, its RMS value equals its peak value divided by the square root of two. The voltage is only at that maximum for an instant; most of the time, it is lower. Multiply RMS by root two: 230 volts RMS gives a peak of about 325 volts. So it means 230 volts RMS: the same heating as 230 volts DC, not a constant 230 volts.