User:Scs/drafts/Magnetic motor

A magnetic motor is a device which strives to convert the force of a magnetic field into continuous mechanical energy. If operated solely by magnetic fields, such a motor would be a perpetual motion machine, and is therefore impossible under every principle of science.

History
The seemingly inexhaustible force obtainable from magnets has long made them attractive to seekers of perpetual motion. Magnetic principles were mentioned in the 1670s by John Wilkins, Bishop of Chester and an official of the Royal Society, who outlined three potential sources of power for a perpetual motion machine: "Chymical Extractions", "Magnetical Virtues" and "the Natural Affection of Gravity". However, no practical magnetic motor has ever been demonstrated.

Fallacy
A magnetic field does not in and of itself create a force or do work. To be sure, the magnetic field of a magnet will attract ferrous metal (generating a force), and the magnetic fields of two magnets will attract or repel each other (again generating a force). If free to move, an object under the influence of a magnetic force will indeed move, but obviously not forever: a magnet can attract and move another object only until the two are touching, at which point motion stops. Similarly, since magnetic fields drop off with distance, a magnet cannot repel another indefinitely, either.

For a magnetic motor to run continuously, therefore, it is necessary to set up a cycle in which one object is attracted (or repelled) through a certain distance, and then somehow returned to its starting point, such that the cycle can be repeated. However, pulling the object back away from the magnet (or, in the case of two repelling magnets, pushing it back towards its starting point) will inherently require the input of precisely as much energy, performing precisely as much work, as was released during the first part of the cycle. The magnetic motor, like all attempts at perpetual motion machines, cannot be a net source of energy or work; it can at best coast until it runs down due to inevitable friction losses.

Similar arguments explain why neither gravitational forces, nor the forces generated by stretched or compressed mechanical springs, can be exploited to create a self-powered motor. In fact, the action of pushing (or pulling) one magnet against another, then releasing it, is almost perfectly analogous to that of compressing (or stretching) and then releasing a spring. A magnetic system (like a system of springs) can be used to store and then release energy (that is, to convert kinetic energy to potential energy and vice versa), but it can never be a net source of energy.

United States
By policy, the United States Patent and Trademark Office does not grant patents for perpetual motion machines, although some devices may slip through the approval process by claiming to be something else. U.S. patent number 3,935,487 is for a "Permanent magnet motor" which generates mechanical power output by the repulsion force between a movable permanent magnet and a fixed permanent magnet. Howard Johnson received three U.S. patents on magnetic motors (in 1979, 1989 and 1995), but as of April, 2012, there is no known successful attempt to replicate the Johnson magnetic motor.