Magnet Myths and Misconceptions

[TinselKoala]

So you noticed the analogy between turning magnets and turning domains in a soft ferromagnetic.
Too bad TinselKoala did not reply to this message about a similar subject.

I'll reply now if you like. My statement was a response to another post where it was claimed that storing energy in magnetic fields was inefficient. I replied by stating that in the general case it was actually very efficient and I gave some examples. Then I attempted to agree with the original claim by stating:

Storing energy by magnetizing  _permanent magnets_ and attempting to recover that stored energy is inefficient.

You responded with a situation that has nothing at all to do with magnetizing permanent magnets and recovering that stored energy, but rather simply shows how moving permanent magnets from one orientation to another within a solenoid stores and recovers energy. You get to do that _once_ in your artificial configuration, then you have to put that energy back in to "reset" back to the mutually repulsive configuration. Try to recover the energy cost from cutting the magnet as in your post, and see how efficient that is!

[TinselKoala]

The "We know how wind works" is another false analogy, because ultimately, wind depends on gravity and energy from the sun to operate. Tinman could easily be asking "how does gravity work" or "how does the sun's energy heat the air". Really, he is asking "Why" questions, not "how" questions. We can usually fully describe "how" these things occur and anyone can look up math formulae at whatever level of complexity they desire to describe and calculate just "how" they happen. The deeper question is "why", and there are many such "why" questions at the bleeding edge where science and philosophy collide. Why is there something, rather than nothing?
Good luck with that one.

How does a magnetic field attract a ferromagnetic substance? The formulae are there for anyone to see and compute with. You can even plug the data into your favorite magnetic simulator and calculate just how strong and in what direction the attraction will be, and this is done every day by motor designers, etc. who actually find that their motors etc. behave as the calculations predict. The "how" is understood pretty darn well.  "Why" does this attraction happen? That's a philosophical question, not a scientific one. 

[MarkE]

@MarkPersonally I have found the laws almost always apply however many people have failed to consider the context in which they are applied. For instance a drop of water cannot climb up a wall against the force of Gravity, it is impossible and violates many known laws of science. Yet this is exactly what one scientist did using an engineered material (nano-material) and he did not break any laws doing it. In fact his experiment did not violate any laws but in fact proved them on that scale.

Excuse me I must have missed that particular law.  What is it known as?  Gravity exerts a force.  Set-up a set of conditions where there is more force up than gravity imposes down and things accelerate upward.

My magnetic bearing is another example and when I told some people I built a 99% passive magnetic bearing based solely on attractive forces they said it cannot be done and violates the laws of science. It doesn't violate the laws of science or Earnshaws theorem because it is 99% passive not 100% and again basically proves the laws but in a completely different context than most would expect.

So either "some people" misunderstood you or they misunderstood the constraints of Earnshaw's theorem.

Thus in my mind it was never the laws which were ever in question but a persons ability to understand the context in which the laws may be applied.

People make mistakes all the time, yes.

At which point we could go one step further and say the laws we know may always apply however we may never know the infinite number of ways in which the context of there application could change.

There is a big difference between an individual misunderstanding a law and whether or not the law is valid.

Almost anything is still possible however it is not a matter of breaking a law but how we interpret and apply it from our own perspective.

Nature doesn't give a hoot what someone understands.  Physical laws get codified because all efforts to falsify the belief fail.  Laws fall or get modified whenever reliable observation shows that a given law does not hold.

The Down wind faster than the wind technology is another perfect example because I didn't see that one coming.

A lot of well educated people did not think that it could work.  But there were no laws that it broke.

I mean I have decades of experience researching and experimenting in aerodynamics but that one caught me completely off guard no matter how obvious it was after the fact.

AC

Individuals make mistakes.  Even SME's make mistakes.  That does not make physical laws into some whimsical smorgasborg that one can choose to ignore.  I remember years ago a debate at between Sean McCarthy of Steorn and a professor of physics, I think at UCD.  Sean McCarthy tried to argue that he was taught that test triumphs theory.  Therefore any test or test claim triumphs theory.  ( Over the years Steorn demonstrated that they very consistently conducted junk tests. )He got handed his head on a plate by the professor.  Reliable experiments drive and challenge theory.  Flawed experiments and flawed interpretations cause temporary distractions, ala N rays.

[NoBull]

You responded with a situation that has nothing at all to do with magnetizing permanent magnets and recovering that stored energy, but rather simply shows how moving permanent magnets from one orientation to another within a solenoid stores and recovers energy.

If you subscribe to the model of a permanent magnets being composed of tiny magnetic dipoles (domains) then it does.
According to that model, the energy stored in permanent magnets is due to the spatial orientation of these domains.
If those domains were allowed to rotate freely (e.g. by exceeding the Curie temperature or cutting up the magnet), then the net magnetic field of a magnet would disappear.

Such disappearance would induce EMF in a coil encompassing the magnet.

You get to do that _once_ in your artificial configuration, then you have to put that energy back in to "reset" back to the mutually repulsive configuration.

Yes, of course.  That's why I asked you about the efficiency of reversibility of such process.

I do not really suggest cutting a magnet up.  Two magnets rotating on a common axis are sufficient to illustrate the process.  They are also magnetic dipoles, just larger...

[MarkE]

If you subscribe to the model of a permanent magnets being composed of tiny magnetic dipoles (domains) then it does.
According to that model, the energy stored in permanent magnets is due to the spatial orientation of these domains.
If those domains were allowed to rotate freely (e.g. by exceeding the Curie temperature or cutting up the magnet), then the net magnetic field of a magnet would disappear.

Such disappearance would induce EMF in a coil encompassing the magnet.
Yes, of course.  That's why I asked you about the efficiency of reversibility of such process.

I do not really suggest cutting a magnet up.  Two magnets rotating on a common axis are sufficient to illustrate the process.

TK will be happy to point to papers on certain EMP weapons that he has in the past that leverage the rapid demagnetization of hard magnetic material by blowing the material up.

The Curie temperature idea could be a fun experiment.  I'd have to ponder a bit on how to perform the experiment safely.  Maybe this can be done by taking an ordinary iron bar as a control and a neodymium magnet as the DUT and placing each successively inside a large diameter coil for thermal insulation and then exposing each to a propane torch.