Current in. Motion out!

A model is an explanation, not a photograph.

Real motors turn tens of times every second, so all the motion here is slowed down a great deal; the supply frequencies are shown slowed down too. Sizes, colors and arrow lengths are chosen to make the ideas visible. The pink force arrows grow in proportion to the force up to a display limit: 0.075 N on the rod and 4 N on each side of the coil. Their scale is fixed within each view; the end view uses the same force dependence as the 3D coil. More field lines are drawn for a stronger field. The curved turning-effect arrow shows torque relative to the maximum at the selected settings. It vanishes at vertical, where the forces act through the axle. Orange arrows show conventional current direction; optional cyan moving markers are direction cues, not individual charges or their actual speed. In the motors, moving arrowheads show current along the coil and supply leads. They reverse in the coil at each DC commutator swap; with AC, they slow down and move back the other way every half-cycle. Playback speed slows the whole model together, including the supply and graphs; the readouts use model time.

The forces and torques in the readouts use real formulas and values: a 5.0 cm rod in the motor-effect view, and a coil with 4.0 cm long sides and an area of 20 cm² in the DC and AC views. The coil is drawn with one loop for about every 10 turns. The motion uses a simple model of friction and air resistance, and the supplies keep the current at its set value; in a real motor the back emf makes the current fall as the motor speeds up. The AC motor is driven only by the force on its coil. That force averages to a steady turning effect only when the coil turns in step with the supply, so this simple motor cannot start itself: something else has to bring it up to speed and let it go at the right moment in the cycle. Here, switching on the supply does that for you, as a starter would. If friction needs more turning effect than the current can give, it drops out of step and slows to a stop. A new frequency is reached gradually, as a real variable-frequency supply would, so a coil in step can follow it. Just after a change it may surge a little faster and slower before it settles.