If we examine the picture closely, we find that both sine waves meet
up at the 0o and 180o points. Furthermore, they both
peak out at 90o and 270o respectively. We say, then,
that both of the two waves produced by the two different generators are
IN PHASE with each
Whenever two waves are in phase, like these are,
the voltage resulting from the two waves will not be the same as either of
the two voltages. The resulting voltage will be the SUM of the two
voltages. In this case, we have 3 and 4 volts being produced by the
generators, and the resulting output voltage would be 3+4 or 7 Volts.
This is because the energy in the two voltages
work together, and combine to add up to 7 Volts. But what happens if the
generators are NOT in phase?