Lorenz-force motors.(MSD 101)

In 1831, Michael Faraday discovered that subjecting a coil to a moving magnetic field induces a current. Today, electromagnetic induction powers most electric motors, along with a phenomenon described in Ampere's law (involving the forces generated between the magnetic field surrounding a current-carrying conductor and an external magnetic field.) But the interaction of the magnetic and mechanical forces inherent to this design is not always the most efficient.

That's why some motors use Lorenz forces instead. Named after the Nobel laureate, this force is that experienced by a point charge moving along a wire in a magnetic field, at right angles to both the current …