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120v /240v residential 180° out of phase

78K views 82 replies 25 participants last post by  backstay 
#1 ·
Back to basics,

For standard residential service I understand that both lines are 180 degrees out of phase and this is why we can get a difference in potential of 240v when both lines are used.

120v + (-120v) = 240v.

But what device creates the out of phase and where is it located?
 
#73 ·
The average voltage of a 60 hz AC waveform is 0 because it crosses above and below the axis in equal amplitudes.

A 120 volt AC signal is actually 340 volts peak to peak. Since the current is varying with time, the average power dissipated by the wave cannot be calculated like DC current. This is where RMS comes in. The RMS value is the equivalent DC value of AC voltage that provides the same amount of power. So even though the AC voltage is 340 volts peak to peak, we like to work with the RMS value of 120 volts so we can do standard power/current calculations.
 
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