superposition principle

Miscellaneous resources found on the web. Please check the copyrights.

Description: In this animation, the graphs show the variation in time of the currents in the vertical and horizontal coils. The plot of the field components Bx and By shows that the vector sum of these two fields is a rotating field. The main picture shows the rotating field. It also shows the polarity of the magnets: as above, blue represents a North pole and red a South pole. © School of Physics UNSW
Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License

Source : http://www.physclips.unsw.edu.au/jw/electricmotors.html