A linear motor is essentially an electric motor that has had its stator "unrolled" so that instead of producing a torque (rotation), it produces a linear force along its length. The concept was pioneered by professor Eric Laithwaite of Imperial College in London. The force is produced by a moving linear electromagnetic field acting on conductors in the field. Any conductor, be it a loop, a coil or simply a piece of plate metal, that is placed in this field will have eddy currents induced in the loop thus creating an opposing electromagnetic field. The two opposing fields will repel each other, thus forcing the conductor away from the stator and carrying it along in the direction of the moving magnetic field.
Because of these properties, linear motors are often used in maglev propulsion, although they can also be used independently of magnetic levitation, as in Vancouver's SkyTrain system and Toronto's Scarborough LRT.
Linear motors have been proposed as an alternative to rocket launchers for lunar launched cargo transport because it would reduce the weight of the launched cargo and so be more energy efficient. Due to air resistance, this type of application is not suitable on earth.