Electrical theory question...
Let's take as an example 50AMP RV service. A voltmeter between the two hots shows 240 volts, between one leg (or the other) and neutral shows 120 volts. My question concerns what happens when each...
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BurbMan wrote:
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This might help:
Perhaps worth noting is that the 120V (nominal) is an RMS voltage, and the peak voltage is considerably higher, around 170V, and correspondingly so also for the 240V measurements.
RMS stands for "root mean square", and is defined as the square root of the average (over time--hence an integral) of the instantaneous voltage squared. This rather odd seeming construction is used because a purely resistive load will consume the same amount of power from a 120V RMS AC supply as from a 120V DC supply, making many computations with ohm's law and such simpler.
Meters are calibrated to show voltages in RMS, though how they determine the reading varies. Some actually respond to the peak voltage and display a scaled value; others to an average value, likewise appropriately scaled; and the best ("true-RMS") are actually measuring the RMS voltage, usually these days through digital sampling and computation. (Traditionally RMS meters measured indirectly by measuring heating in a known load; this is accurate but rather expensive to implement.) The difference matters a great deal when attempting to measure decidedly non-sinusoidal signals.
