I am a second year electrical Engineering student and so far I have been picked up that Vrms is the component of a rectified ac signal that will deliver the same power as dc. But now I am told that Vdc = 0.318Vm and Vrms =0.707 which is not the same. Confused.
You had better get a good understanding of RMS, or you are in for a rough, tough ride in the electrical field.
RMS is the equivalency factor with respect to the power. For instance, you cannot expect a sine wave to output the same average power that a constant amplitude voltage/current does when both have the same peak value. In fact, a 1 volt peak sine wave outputs only 70.7% of the power a 1 volt constant amplitude source would produce. That is because the sine wave dips down to zero twice during each period.
To figure the root-mean-square (RMS), take the square of the wave value of every instant of time during an appropriate period. Next, find the average of the squares. Then take the square root of that average. Below are some sample calculations for a sine wave. The square is necessary because power is proportional to the square of voltage/current.
An average responding meter only measures full sinusoidal waves accurately. For other waveforms, use a true-RMS meter which calculates the RMS value like I did above.
Ratch