Sorry I screwed up let see how can I word this
The power source is always with in phase it is what we are
powering up in order to run you must change the phase
example if you have three phase motor each phase
will be 120 degree out of phase but if you have single phase
motor primary windings must change phase by 90 degrees
in order for motor to start up, that is what centrifugal switch is
use for and capacitor, if this is not done motor will simply sit
there and humm, this two setups are must common types for
motor starting configurations in industries. on the pure resistive
load there is no phase shift.

Look in any system if you have two wires going to a load each
wire will carry same amount of current it does not matter if is
120 or 220 or 480 if is light to be light or motor to be run both
wire/legs will carry identical current regardless if is neutral or hot,
positive or negative current is equal in both legs, in three phase
system current will depend on the balance of electrical components
to be powered and voltage supplied this are basics and they
do not change

By the way 180 degree shift is never use that I know of in
electrical use however in electronics yes and terminology
is antiphase, it is use in amplifications (tube type)