Hello, the R.M.S. value of a current composed of a number of sinusoids of different frequencies and any phase angle is given by Irms=SQRT(I1rms2 + I2rms2 + ...) where SQRT is for the square root function and the terms inside it are the square of the r.m.s. value of the amplitude of each component sinusoid. A current i(t)=6cos(25t)+5sin(30t)+4 A is causing the trouble. Had the 4A (d.c.) component been absent, we would have had the rms value for this current as 5.523 A rms. But how do we take the 4 A d.c. current into account for the calculation of the r.m.s. value of this current. The answer given in text is 6.82 A rms. Help is sought.
