Select the phase angle to see how magnetic field changes.
Hover on sinusoidal diagrams to control the position.
With relative phase of 90°,
the field obtained by the sum of the two pulsating
fields is circular.
For other values it becomes elliptical.
Shifting the phase angle by 180° reverses the sense of rotation.
This is achieved in practice on motors by inverting the electrical
connection of one of the two coils.