Then there was root-mean-square (RMS) voltage. For those nice sine waves, you took the peak voltage and divided by the square root of two, 1.414 or so. You know that kid in the front of the class?
The r.m.s. value of an a.c. signal is equal to the value of direct current (d.c.) which would have the same effect or energy change as the a.c. The r.m.s. voltage of an a.c. signal is always less ...