720. How does an electric motor work? - BR
An electric motor uses the attractive and repulsive forces between magnetic poles to twist a rotating object (the rotor) around in a circle. Both the rotor and the stationary structure (the stator) are magnetic and their magnetic poles are initially arranged so that the rotor must turn in a particular direction in order to bring its north poles closer to the stator's south poles and vice versa. The rotor thus experiences a twist (what physicists call a torque) and it undergoes an angular acceleration—it begins to rotate. But the magnets of the rotor and stator aren't all permanent magnets. At least some of the magnets are electromagnets. In a typical motor, these electromagnets are designed so that their poles change just as the rotor's north poles have reached the stator's south poles. After the poles change, the rotor finds itself having to continue turning in order to bring its north poles closer to the stator's south poles and it continues to experience a twist in the same direction. The rotor continues to spin in this fashion, always trying to bring its north poles close to the south poles of the stator and its south poles close to the north poles of the stator, but always frustrated by a reversal of the poles just as that goal is in sight.