Definition of Root Mean Square (RMS)
The most common method or specifying the amount of a sine wave of voltage or current is by relating it to dc voltage and current that will produce the same heating effect. This is called its root-mean-square value, abbreviated rms.
Formula for RMS:
- RMS Value = 0.707 × Peak Value
Or we can say
- Vrms = 0.707 Vmax and Irms = 0.707 Imax
With a peak of 170 V, the sine value is 0.707 × 170, or 120 V, approximately. This is a voltage of the commercial ac power line, which is always given in RMS value.