David, The following paper presents (literally) a toy example of extracting energy from a static magnetic field:
"A Magnetic Linear Accelerator" http://www.physics.princeton.edu/~mcdonald/examples/lin_accel.pdf It provides a simple formula illustrating conversion of magnetic field energy to kinetic energy. While it does not completely answer your excellent question, it's a starting point. -- Lou Pagnucco David Roberson wrote: > Recently I have been exploring magnetic concepts. I have been seeing so > many references to magnetic motors that I believe are not possible, but > they keep coming so I decided to perform some thought experiments. Let me > present one that is somewhat associated with the motor concepts. > > > All I ask is that you give it some serious consideration and post what you > think the results should be. > > > Take an iron rod and wrap a coil around it. The rod is initially not > magnetized. > > > Apply a voltage to the wire for a short period of time that allows enough > current to flow to result in a permanent magnetization of the iron rod. > > > Now, if you are very good at measuring energy, you would be capable of > directly measuring the input energy supplied by the voltage source. > Record this energy for later reference. > > > At this point in time, the rod maintains a magnetic field that contains a > certain amount of field energy and heat has been given off due to losses > within the wire and due to mechanical effects within the rod, etc. > > > I would assume that we would now have a direct measurement of the energy > stored within the field so it is time to make it do some work. > > > Take a large collection of iron pellets that are not magnetized and work > with them one at a time. Attach a scale to the first one that records the > attraction force between the magnet and the iron pellet. Allow the pellet > to slowly approach the magnet while you record the force applied. > Integrate the force times distance to arrive at the work performed by the > action of the field upon the pellet. > > > Now, continue to add pellets one at a time while your record the work > performed upon each one. Continue this operation until either one of two > things happen. The first is that there is no more force available to do > work on additional pellets. The second is that you run out of pellets > after a large pile of them is attached to the magnet. > > > The question becomes: Does the external field become zero just as all of > the energy applied to generate it by the voltage source less losses is > exactly equal to the work done on the pellets? Or, does the net energy > supplied by the pellet motion end up as some fraction of the initial field > stored energy while leaving some if not most of the field energy intact > but contained within the pile of iron? Or, would you suspect that the > field would never cease to supply energy to additional pellets since it > expands due to the extra iron? Any other possibilities? > > > My bet is placed upon the second condition. I would expect the > COE(conservation of energy) to limit any work that can be taken from the > rod to a value that is less than the initial field energy, but that much > of the field would be left contained within the iron pile. > > > What do you others think will happen? Can we obtain infinite energy with > such a system? > > > Dave >
