Root mean square

Root mean square - 25 Now you average those values...

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Root mean square This average value we use for the voltage from a wall socket is known as the root mean square, or rms, average. Because the voltage varies sinusoidally, with as much positive as negative, doing a straight average would get you zero for the average voltage. The rms value, however, is obtained in this way: first, square everything (this makes everything positive) second, average third, take the square root of the average Here's an example, using the four numbers -1, 1, 3, and 5. The average of these numbers is 8 / 4 = 2. To find the rms average, you square everything to get 1, 1, 9, and
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Unformatted text preview: 25. Now you average those values, obtaining 36 / 4 = 9. Finally, take the square root to get 3. The average is 2, but the rms average is 3. Doing this for a sine wave gets you an rms average that is the peak value of the sine wave divided by the square root of two. This is the same as multiplying by 0.707, so the relationship between rms values and peak values for voltage and current is: V rms = 0.707 V o and I rms = 0.707 I o In North America, the rms voltage is about 120 volts. If you need to know about the average power used, it is the rms values that go into the calculation....
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