"The number of applications that use magnets just seems to be getting larger and larger," he says. "A lot of the materials are mined in China, and so the price can often depend upon our trade status with China." Hofmann adds that Tesla recently started using permanent magnets in its motors. Electric motors use rotating electromagnetic fields to spin a rotor. Coils of wire in the stationary outer portion of the motor, called the stator, produce these electromagnetic fields. In permanent magnet motors, magnets attached to the edge of a spinning rotor produce a magnetic field that is attracted to the opposite poles on the spinning field. This attraction spins the rotor.