Chapter 3.2, Problem 38BB

Quadratic Mean The quadratic mean (or root mean square, or R.M.S.) is usually used in physical applications. In power distribution systems, for example, voltages and currents are usually referred to in terms of their R.M.S. values. The quadratic mean of a set of values is obtained by squaring each value, adding those squares, dividing the sum by the number of values n, and then taking the square root of that result, as indicated below:

Quadratic mean = $\sqrt{\frac{{\displaystyle \sum x^2}}{n}}$

Find the R.M.S. of these voltages measured from household current: 0, 100, 162, 162, 100, 0, −100, −162, −162, −100, 0. How does the result compare to the mean?