|MadSci Network: physics|
Here are two examples of perpetual motion machines, how they work and don't work.
http://www.geocities.com/SiliconValley/Bay/9208/motion.htm (defunct as of 5/2006, see http://www.geocities.com/k_pullo/PM3.htm as a possible alternative)
For the first, the author mentions the machine might work if the magnetic field could be focused. That, perhaps, was intended as a subtle way of saying the machine could not work. There are only a few ways of focusing a magnetic field, that I can think of. One method is to shield the area or areas where the field is not desired with a Faraday cage. The Faraday cage doesn't work though unless the shielded region is completely enclosed by the cage. It is also possible to alter a magnetic field by introducing one or more other sources of magnetic fields. Tokamak-style fusion reactor concepts are an example of technologies used to effect desired magnetic field configurations. The third method that comes to mind is to vary the source, which is the method used in the perpetual motion machine described above.
With the Faraday cage, it is not possible to open up one side of the cage to cause just the right amount of magnetic field to stream through. Instead, if the Faraday cage is opened, the magnetic field is re- established inside the cage as if the cage were not present. Note that a Faraday cage can be constructed from such materials as chicken wire, so that opening a Faraday cage implies the cage was altered sufficient to allow encroachment of the magnetic field - the cage is inherently closed or open.
Attempting to alter one magnetic field by introducing one or more others simply changes the magnetic field overall and does not provide for the focusing effect needed by the above machine - unless at the expense of the surrounding environment, meaning the machine might be made to work but could no longer be considered perpetual because it consumed more energy than it produced.
Perpetual motion machines and other energy from nothing concepts have been around for all time and new ones will continue to be proposed. It is sometimes a challenge to determine what assumptions have been made in the design, but one of those assumptions is always the source of the error.
For more on Faraday cages, see the following sites:
For more on magnetic confinement, see the following sites:
For more on perpetual motion machines, see the following sites:
Try the links in the MadSci Library for more information on physics.