The normal value with which we refer to the voltage is called the rms voltage. It is the root mean square of the instantaneous voltage supply

V

_{rms}= Sq. root (v

_{1}+v

_{2}+v

_{3}+v

_{4}.....v

_{n})/n

Where v

_{1}, v

_{2}, v

_{3}and v

_{n}are the instantaneous voltages.

The relation between the rms voltage and the peak voltage is as follows.

V

_{rms}= 0.707 x V

_{peak}