Why won't magnet motors work
Date: Tuesday, April 12, 2005 @ 22:14:16 UTC
Topic: Science


In the yahoo free_energy group Phil Karn writes: Mr. J wrote:
> Ok -
>
> I don't know much about magnets or the physics of
> them. I suspect nobody else does either... oh yea..
> negative attracts positive... etc., kind of
> tautologies to me. Sort of like gravity.. it just
> works.. we have no clue how.. etc.,
>
> Anyway, what is the simple explanation of why magnetic
> motors shouldn't work?

The answer is both simple and profound. Magnetism is what physicists call a "conservative force". That means if you take a magnet and move it between any two points in a magnetic field, the sum total amount of energy produced or consumed in the process is a constant that doesn't depend at all on the path or speed you take between those two points.

Furthermore, if the starting and finishing points are the same, then the total energy involved in moving over *any* path and returning to the starting point is exactly ZERO.

The same is true if you move a mass between two points in a gravitational field, because gravity is also a conservative force.

For example, if you want to move a car between two points that differ in elevation above sea level, and if you ignore air drag, rolling resistance and other forms of friction, then it doesn't matter what route you take between the two points or how fast you drive. If the finish point is higher than the starting point, you'll have to add a certain amount of energy; if the finish is lower than the start, it will produce a certain amount of energy. If you drive in a closed path and return to your starting point, the total energy will be exactly zero.

Real cars always require energy to drive because gravity is not the only force at play, or even the dominant one; aerodynamic drag and rolling resistance usually overwhelm the effects of gravity on vehicles on the earth's surface. These are both forms of friction, and friction is *not* a conservative force. With friction you *always* lose, though with clever design you can minimize it.

One place where friction is almost completely absent is outer space. There, satellites demonstrate gravity's conservative nature quite nicely. A satellite in an elliptical orbit speeds up when it approaches the earth and slows down as it climbs to high altitude. The process repeats more or less forever, with the satellite's total mechanical energy remaining constant unless it is perturbed by a third body into hitting the earth's atmosphere or some other object.

Any would-be perpetual motion machine using either magnets or gravity is subject to the very same rules. Even if you completely eliminate friction, the net total energy produced and consumed in returning all the machine's masses or magnets to their original starting positions in a complete cycle will always be *exactly* zero.

It's extremely common for a would-be perpetual motion inventor to get really excited when his machine produces energy over one part of its cycle. But this energy is *ALWAYS* exactly equal to the energy the machine needs to return to its starting point and complete a cycle. They never figure out how to get their machines to run in complete cycles while also producing useful energy, because it simply can't be done.

This is *always* true. It doesn't matter how many magnets or masses you have or how clever you are or complicated you make your machine. It won't work, and there's absolutely nothing you can do to make it work.

--Phil

Mr. J wrote:
> Phil -
>
> Thank you for taking the time to write. Now I think I
> have more questions.
>
> Does a "conservative force" imply without fluctuations?
>

A conservative force will remain exactly constant under a given set of circumstances. Put two magnets of a given strength a given distance apart, and the force between the two will remain the same for all time. Put two given masses a given distance apart, and the force between the two will also remain constant for all time. In that sense, conservative forces can't "fluctuate".

If you could make a conservative force fluctuate, then you could generate energy from nothing, e.g., by turning off gravity after you've let a boulder fall so you can return it to its starting point without any energy. But that's not possible.

You *can* make a magnet that switches on and off. It's called an electromagnet, and unlike a permanent magnet you can do work with it. That's exactly how electric motors work. But any work you do with an electromagnet must come from the electricity supplying the magnet; again there is no free lunch.

> Is a magnet conservative because it has two equally blanced
> yet opposite forces? But gravity seems to be one way,
> everywhere in at the same time.

No, gravity is always an attractive force, but it's just as conservative as magnetism. A "conservative" force is just as I described in my last message: the energy required or produced in the process of moving a particle from point A to point B in the force field is the same no matter what path is followed (and what speed is taken) between those two points. Furthermore, if points A and B are the same (the motion is in a closed loop) the total net energy will always be exactly zero.

> If friction is a always a loser, where/what is the
> anti-friction? Otherwise wouldn't our universe have
> gone cold by now? Or is electromagnetism in general the
> lubricant? The earth is a big magnet with two poles.
> Maybe a magnet is by its own nature anti-gravitational?

A lot of people have wondered why there isn't an "anti friction". The reason there isn't such a thing has to do with the second law of thermodynamics, the one that says that the entropy of any closed system always tends to increase over time. No process exists that can reduce the entropy of a closed system, although the entropy of a subsystem can be decreased if there is an equal or larger entropy increase elsewhere. That's how life could spontaneously evolve on the earth: the entropy reduction in the "ordering" of life is more than made up for by the enormous entropy increases caused by thermonuclear fusion in the core of the sun.

The Second Law is one of the more "depressing" of all physical laws, because it's the one that says the entire universe will some day "run down" and become completely disorganized and random. (When the sun dies, all life on the earth will eventually die as well.) Friction is a classic example of an entropy-increasing process, and because there are no entropy-decreasing processes, there is no such thing as "anti friction". It sure would be nice if there were, but there ain't.

--Phil






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