section_path: Advanced types/Linear
section_name: Linear
paragraph_text: Linear
  
  A linear motor is essentially any electric motor that has been "unrolled" so that, instead of producing torque (rotation), it produces a straight-line force along its length.
  
  Linear motors are most commonly induction motors or stepper motors. Linear motors are commonly found in roller-coasters where the rapid motion of the motorless railcar is controlled by the rail. They are also used in maglev trains, where the train "flies" over the ground. On a smaller scale, the 1978 era HP 7225A pen plotter used two linear stepper motors to move the pen along the X and Y axes.