The rotor is the component of the SmartMotor that rotates inside the stator coil. The rotor is surrounded by a permanent magnetic. Electric currents in the stator coil create a changing magnetic field. This magnetic field reacts with the magnet field around the rotor and causes the rotor to turn. The stator contains a number of coils. In a simple design of motor, the rotor will rotate in such a way that its magnet tries to stay in alignment with the field generated in the stator coils. At slower speeds, the rotor turns in small steps or jerks, not with a smooth uniform motion. This effect is known as torque ripple. By building the rotor with a twist, or making a skewed rotor design, the permanent magnet is twisted around the rotor shaft. This causes a corresponding twisting of the magnetic field. The field of any one rotor-magnet is now spread just beyond one of the stator coils. The result is a much smoother rotation and considerable reduction in torque ripple.