What is rms value?
The RMS value is the effective value of a varying voltage or current. It is the equivalent steady DC (constant) value which gives the same effect. For example, a lamp connected to a 6V RMS AC supply will shine with the same brightness when connected to a steady 6V DC supply.
Why do we use Root Mean Square (RMS) values when talking AC circuits?
Attempts to find an average value of AC would directly provide you the answer zero... Hence, RMS values are used. They help to find the effective value of AC (voltage or current). This RMS is a mathematical quantity (used in many math fields) used to compare both alternating and direct currents (or voltage).
relation between vm and vrms?
The mean value of a time-varying function is defined in terms of an integral. An associated quantity is the root-mean-square (r.m.s). For example, the r.m.s. value of a current is used in the calculation of the power dissipated by a resistor.
