Magnetic force in a simple commutated motor follows the right-hand rule: if the index finger shows the direction of electric current $I$ (which moves the electric charge $q$) and the middle finger shows the direction of magnetic field $B$ (flux density), then the thumb shows the direction of magnetic force $F$ acting on the moving charge; the force is proportional to the length of wire $l$ exposed to the magnetic field.
The drawing was inspired by:
- http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html {accessed 2021-06-08}
motor_force_magnetica.png
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