JWelectric
Electrical Contractor/Instructor
A couple of key things that needs to be addressed by the author of this Wiki post is the relationship to the neutral and the use of the word voltage.[1] The two halves are 180 degrees apart with respect to center point. It may also be called three-wire, single-phase, midpoint neutral system.
First is the voltage which is nothing more than the amount of pressure that is pushing the electrons around on the conductor. Voltage is not kinetic and does not move. Voltage changes polarity or the direction of the pressure.
What is moving is the electrons and the movement of electrons is measured as amps and called the current of the circuit. As the pressure or volts starts from zero and climbs to a peak the current flow starts from zero and climbs to a peak. The relationship of the current and voltage will depend on a couple of things. Is the circuit inductive or capacitive. The sine wave of the current to voltage will either lag or lead depending but for the sake of this post it will be in sync.
A dryer is a 240 volt appliance that also uses the neutral. The heating element is 240 volts but the motor and controls are 120 volts. Current will leave the transformer and return to the transformer for both voltages. The current will travel first clockwise then counter clockwise changing 60 times a second.
Put the controls on one leg and the motor on the other leg with the heating element on both legs. As the current leaves the transformer on leg A and is returning on leg B in a clockwise direction both the control and motor will see a clockwise movement of the current. The controls will see current moving clockwise from A to N and the motor will see current moving clockwise from N to B.
What the author of the Wiki post is saying is that if we were standing on a railroad track and looked first in one direction then we would have to turn our direction of sight 180 degrees to look in the other direction. This looking first one way then the other way does not change the fact that the railroad track is in one straight line going from point A to point B. It simply means that in order to looking first one way and then the other we as humans must turn 180 degrees. Also notice that the author said nothing about anything being 180 degrees out of phase.