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Originally posted by Amagnon
An electromagnetic field, such as that produced by a permanent magnet, can be used to do work over and over again. You can pick up paper clips all day - it wont wear it out.
The "life" of a permanent magnet depends on many factors. Naturally occuring forces conspire to knock the little domains out of alignment. But this is normally a very slow process. Temperature is a major player in this process. The higher the temperature, the faster this process will occur. Extreme heat [surpassing the curie point] will immediately randomize the domains. A sharp blow can also knock domains out of alignments, as can other nearby magnetic or electrical fields. Radiation can also knock domains out of alignment.
Many motors use permanent magnets (usually rare earth strong type). In this cases, there a few things that can demagnetize them, and thus must be avoided:
-extreme temperature (Currie temperature I think?)
- Too high of current (and thus magnetic field from the coils)
- damage from dropping, bashing, or even disassembling the magnets.
So, although permanent magnets can quickly become demagnetized, in such an application, you have to know at what temperature, current, etc this occurs, and design your system to avoid it.
How long will a permanent magnet last?
A permanent magnet will retain its magnetism unless it is affected by a strong outside magnetic or electrical force, or elevated temperatures. If they are not exposed to any of these conditions, permanent magnets will lose magnetism on their own, however this degradation is very slow, on the order of one percentage point every ten years or so.
Can a magnet lose its magnetism?
Yes, if a magnet is influenced by another strong magnet, is affected by a powerful electrical force, or is exposed to temperatures above a certain level, it may lose some or all of its magnetic strength. Be sure to identify the properties of the magnet in question before using it if loss of strength is a concern.
Originally posted by cupocoffee
reply to post by buddhasystem
It's incredibly consequential!
How is it that, as long as you are kind to your permanent magnet and take precautions to preserve its field strength, as Arbitrageur has outlined for us, that it can do real work and cause objects to accelerate, over and over and over again, for years, without consuming ANY fuel whatsoever and barely losing any field strength?
Originally posted by cupocoffee
Once again you avoid the question of where magnets get the energy to do work from. No big surprise there.
Originally posted by cupocoffee
reply to post by buddhasystem
Once again you avoid the question of where magnets get the energy to do work from. No big surprise there.
Originally posted by buddhasystem
Oh please. There is plenty of energy spread around the Universe. Nuclear weapons is one shining example. As I said before answering the same inane question,
you can drive to the Grand Canyon and jump off the rim. Rest assured gravity will do work on your sad body. That doesn't mean that you can extract energy from vacuum, by jumping into the Canyon multiple times, even if you were to survive the fall.
I used to think so, but I've seen enough reports like these to make me wonder:
Originally posted by buddhasystem
reply to post by Arbitrageur
Cher Arbitrageur,
this is completely inconsequential. I don't care is permanent magnets get ruined in the alleged "perpetual motion" machine just after two cycles. The point is that you can't make even one over-unity cycle.
I know a few people who built a device like this and they had a similar result, where it would spin faster and faster until it either fell apart, or until the magnets were depleted and had to be recharged (resulting in a net loss in overall energy).
Of course it's possible to build something with magnets that will spin for a while. Many people have done it. But eventually it will demagnetize and slow down, and end up losing more energy overall than was gained.
All alleged motors (spinning or not) have one thing in common and that is they produce virtually no excess torque. As soon as a load is placed the thing will halt. A motor that cannot work under a load is not practical.
Another thing is the energy isn't infinite nor free. So even if it were possible to create a spinning motor, placing magnets within the field of other magnets will gradually wear down the flux.
Originally posted by Arbitrageur
So according to his explanation, extracting the work while the magnets are becoming demagnetized is like accelerating into the grand canyon. You change some "potential energy" into "kinetic energy" but to repeat the cycle you have to put a lot of work into the system, either traveling back up to the rim of the grand canyon, or re-magnetizing the magnets.
So I don't know if it's true or not but if it's really only 20% efficient as one experimenter explained it, then it's not really over unity any more than jumping into the grand canyon is.
Originally posted by -PLB-
Originally posted by cupocoffee
Once again you avoid the question of where magnets get the energy to do work from. No big surprise there.
I think you are confusing the magnetic field with energy. The energy required for attracting a piece metal over and over is coming from the actor that removes the piece of metal again after it has been attracted. The required energy to do this is at least equal to the energy you can ever generate by attracting a piece of metal. In practice the required energy to do this is alway more. The magnetic field however can remain for a long period. But the field itself is not generating any energy.
That is why machines like the one in this topic will never work. It is a nice fantasy, but nothing more than that.
Originally posted by cupocoffee
reply to post by -PLB-
The constant acceleration vector toward the Earth is what creates the orbit in the first place.
Originally posted by -PLB-
reply to post by cupocoffee
An object in orbit is in constant free fall yes, but its velocity is constant, the object does not accelerate. So no energy is generated nor required to keep it in orbit.
The ISS orbits at a relatively low altitude, so as to make it easily accessible from Earth. The downside of this, however, is that the ISS experiences fairly high levels of atmospheric drag, making periodic boosts of altitude necessary. Currently, altitude reboosting by chemical rockets fulfills this requirement. If the tests of VASIMR reboosting of the ISS goes according to plan, the increase in specific impulse could mean that the cost of fuel for altitude reboosting will be one-twentieth of the current $210 million annual cost.
Originally posted by Arbitrageur
But I'm not sure what your point is.