Simple generator with a commutated rotor: if the index finger shows the direction of velocity $v$ of the electric charge $q$ displacement (due to the conductor movement driven by the torque) and the middle finger shows the direction of magnetic field $B$ (magnetic flux density), then the thumb shows the direction of the magnetic force $F$ acting on the charge and inducing the electromotive force EMF.

The drawing was inspired by:

• http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html {accessed 2021-06-08}

generator_force_magnetica.png