RMS Values

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Here is another fundamental concept thats not too hard, yet important ....adding the RMS values of currents.

1 + 1 = 2 (Unless You're an EE)
What that means is that if you read the currents in the example below with an amp-meter, (where current A splits into currents B and C) cable B would read 1 amp, cable C would read 1 amp and cable A would read 0 amps.
(1 + 1 = 0?)

No...its not the "new math". All of the examples, to this point, have been adding currents at an instant of time, thus INSTANTANEOUS CURRENTS. The meter, however, tells us the average magnitude of the sine wave, disregarding the fact that half of it is negative. It simply inverts the negative half of the sine wave and then averages all the values (called 'root mean squared, or RMS). The RMS value is 0.707 of the peak value of a sine wave, or put in other words, the peak value of a sine wave is 1.414 times the RMS value. An example using voltage would be that 110 volts at a receptacle on the wall is the RMS value representing a sine wave with a peak value of 155.5 volts.

Anyhow, you can't directly add RMS values unless they are in-phase (meaning that the sine waves peak and fall at the same time).

We'll learn how to add RMS currents when we discuss "vectors" and "phasors" in the Power Triangle section....it's easy!

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