If an electric motor did not reverse the direction of its current every half-turn, what would be observed in the armature? Would it spin from left to right clockwise, then spin back anti-clockwise from right to left? Or would it spin left to right clockwise and halt once it’s turned 90º, halfway between the two magnetic poles (I saw this somewhere and it puzzled me)?
If I guess at the type of motor involved, if the current is not reversed, the armature will spin to the point of equilibrium with the stationary magnets and it will stop. I may due to momentum slightly overshoot the equilibrium point, but it will settle down to stationary.