Induction Motors

Here we see Lenz's law in action. The field is continuously changing. The coil, thanks to the field induced in it, does its best to keep up with it and rotates. There is no commutator or slip rings so induction motors are very reliable.

Here is a more complicated set up. A 3 phase induction motor. There are 3 pairs of coils each supplied by a different phase of a 3 phase supply. The 3 phases are all 120⁰ out of phase with each other.

This produces a rotating field which the rotor coil does its best to keep up with.

Another refinement. Why bother with a rotor coil. Below is a squirel cage rotor. Emf's and eddy currents flow where they want to.