Getting a handle on electromagnetism

[crashsite]

I know that sounds pretty general...and it is...

As I understand it (or maybe don't), "magnetism" is actually an electrical force brought about by the alignment of the spin axes of electrons. Under the influence of electrical current, the alignmnets will occur in any conductor (thus the "electromagnetism" link) and all electrical fields have the magnetic component.

But, some materials will retain some of the electron spin alignmnets even when the electrical current is not present. Iron, nickle, cobalt, aluminum and other elements being the most common.

What's more, they can also be magnetized without the electrical current simply by moving then relative to each other so their fields interact (although that may very well be the result of currents that are generated by such an action).

When the magnetic influence (field) is static and encompassing a conductor, nothing happens but, when either the field varies or the concuctor moves within the field, electrical cureent is generated in the conductor.

If the electrons are dynamic (spinning and orbiting), why isn't the current being generated any time the magnetic field encompasses a conductor? Just intrisically, it sort of seems like the spin alignment should interact with the electrons in the conductors (much as it seems to interact with the electrons in another magnetized object) regardless of relative movement.

Now, I realize that I'm getting pretty close to some sort of, perpetual motion type concept here and, that's not allowed but, I'm only trying to sort out just exactly how this does work.

I'm sure there's a complex mathematical series that explains this but, is there also a simple, essentially "mechanical" answer, too? Have I missed the point either a little or a lot?

 

[dknguyen]

It's electromagnetics. So the there is no mechanical answer in the same way how a plane flies only has a mechanical answer and can't be explained in electrical terms.

Some materials have very small, infintesmal "ferromagnetic domains" which are like "little magnets" scattered throughout the substance. SUch as iron, nickel, etc. These domains are normally all pointed in random directons and the combined magnetic field of each doman cancels out so you normally have no magnetic attraction. When placed in a magnetic field these domains realign and produce a net magnetic field becoming a magnet itself. If this external field is removed the domains pop back into their random alignment.

If you are able to realign these domains to point in the same direction and "lock it" in place without the need for an external field the material becomes a permanent magnet. One way is by melting the material, sticking it in a magnetic field so the domains align themselves and then letting the material cool to lock the domains in place and then removing the magnetic field. I think that's about as a mechanical answer as you can get- think of it like a pile of dust where each particle is it's own magnet.

If the electrons are dynamic (spinning and orbiting), why isn't the current being generated any time the magnetic field encompasses a conductor? Just intrisically, it sort of seems like the spin alignment should interact with the electrons in the conductors (much as it seems to interact with the electrons in another magnetized object) regardless of relative movement.

Are you talking about electrons orbiting a nucleus? I'm going to go on a limb and say the sum of the orbiting is RANDOM thus cancelling out any magnetic field. Electrical current is not from electrons orbiting a nucleus but from them moving amongst atoms. Also, with regards to spinning and orbiting being dynamic- it may not be considered dynamic if the spin and orbit is constant in the same way an object that is moving is not dynamic if it is moving at a constant velocity. Yes, the moon orbiting the earth might be considered dynamic because there is an acceleration, but it might not be so with an electron because things on the subatomic level do not necessarily have very good analogies to "macro atomic" phenomena. But even if it was dynamic the randomness and unsychronizedness of the orbits would cause a summing to zero. *This paragraph is speculation.*

Also, from: https://en.wikipedia.org/wiki/Ferromagnetic

The spin of an electron, combined with its orbital angular momentum, results in a magnetic dipole moment and creates a magnetic field. (The classical analogue of quantum-mechanical spin is a spinning ball of charge, but the quantum version has distinct differences, such as the fact that it has discrete up/down states that are not described by a vector; similarly for "orbital" motion, whose classical analogue is a current loop.) In many materials (specifically, those with a filled electron shell), however, the total dipole moment of all the electrons is zero (i.e., the spins are in up/down pairs). Only atoms with partially filled shells (i.e., unpaired spins) can experience a net magnetic moment in the absence of an external field. A ferromagnetic material has many such atoms, and if they are aligned they create a measurable macroscopic field.

If correct, that probably explains what a "ferromagnetic domain" actually is.

 

[crashsite]

The Permanent Magnet Conundrum

It's electromagnetics. So the there is no mechanical answer in the same way how a plane flies only has a mechanical answer and can't be explained in electrical terms.

Actually, I've sort of become convinced, over the years, that everything (including, possibly nothing) is electical (and, possibly gravitational) and has an electrical explanation.

Some materials have very small, infintesmal "ferromagnetic domains" which are like "little magnets" scattered throughout the substance. SUch as iron, nickel, etc. These domains are normally all pointed in random directons and the combined magnetic field of each doman cancels out so you normally have no magnetic attraction. When placed in a magnetic field these domains realign and produce a net magnetic field becoming a magnet itself. If this external field is removed the domains pop back into their random alignment.

Okay, I don't have a problem with that or the next part about, locking the magnetic comains in place to form permanent magnets. I guess the (problem, confusion, wonderment, angst, et.) relates to the current vs. magnetic domains.

Are you talking about electrons orbiting a nucleus? I'm going to go on a limb and say the sum of the orbiting is RANDOM thus cancelling out any magnetic field. Electrical current is not from electrons orbiting a nucleus but from them moving amongst atoms.

There obviously is an interaction between the magnetic domains and the electrons of the atoms in a conductor. I guess I tend to think of it as the moving magnetic field sweeping electrons in the conductor toward one end, making it the negative terminal. But, does it automatically make sense that the magnetic field must be changing for that to happen?

If it were not for permanent magnets, I'd say, "sure, why not". The magnetic field is created as a result of the interaction of the current with the atoms and one effect creates the other. Like blowing one fan into another to make it spin. In the electrical circuit there are losses so, no fear of creating a "Flubber" effect.

The permanent magnet is the conundruim. If the magnet is there and the electrons in a conductor are under the influence of it's field, why aren't electrons pushed to one end of the wire...even if the field is static? You can easily say, because there's no force being applied to do the sweeping.

But, if two magnets are brought to close proximity, their magnetic fields do indeed interact to either attract or repel the magnets. There is a force even in the absence of movement. So, I guess maybe the right question is whether there is a completely different branch of physics in play depending on whether you are dealing with magnetic fields as they relate to electric currents as opposed to dealing with permanent magnets (or magnets during the time they exist because of the effects created by current flow)?

I mentioned the perpetual motion aspects so, certainly I'm not the first person to notice these things and question just what the heck is going on. There seems to be a "force" or "energy" associated with magnets that defies conventional physics but, it's just as obvious that there is a physics to it (although sometimes it looks downright spooky...like the levitating superconducting magnet we've all seen pictures of).

I also realize that we're dealing with pretty much a different universe when we get down to the atomic level and that maybe you are right that there is no Newtonian Macro Explanation possible to explain magnetic effects. Frankly, I'm still suspicious that gyroscopes are "real". It's just not possible that simply making something spin will stabilize it, right?

 

[Nigel Goodwin]

It's just not possible that simply making something spin will stabilize it, right?

You mean like arrows, darts, bullets etc.

 

[Sceadwian]

Force is NOT energy. The static magnetic repulsion force isn't free energy for the takeing it's just a force, much like gravity. You can store energy in a gravity field by increasing the distance between the relative masses, like you can store energy in the magnetic field by pushing the to interacting fields closer together, the energy released when restricting forces are removed does not come from the fields themselves but from the kinetic energy stored in them. The fields themselves are simply enablers of energy exchange.

 

[crashsite]

Mysterious Forces

Force is NOT energy. The static magnetic repulsion force isn't free energy for the takeing it's just a force, much like gravity. You can store energy in a gravity field by increasing the distance between the relative masses, like you can store energy in the magnetic field by pushing the to interacting fields closer together, the energy released when restricting forces are removed does not come from the fields themselves but from the kinetic energy stored in them. The fields themselves are simply enablers of energy exchange.

In the electromagnetic example, this makes sense. It takes energy to build the field and the energy is released when the field collapses. Even when there's residual magnetism, one can assume that the energy to create the permanent magnet had come from somewhere and is energy trapped in the material rather than being released when the electromagnetic field collapses.

Anyone who's ever played with magnets (presumably everybody there), knows that it takes, "effort" to hold magnets together when they are N to N or S to S or to hold them apart when N to S. We expend more calories even when there is no movement than holding objects of identical size and weight with no magnetic interaction. There are other imperical examples as well.

In the "levitating super magnet", you actually remove energy from the system until it is cold enough for the material to go superconductive and then it actually rises against gravity and hovers. Some force or energy is creating that movement and resistance to the gravity.

Even if there were an effect where magnetic fields of permanent magnets would diminish, in accordance with some law of physics as the magnetic field was utilized, one could say, "Okay, there's an exchange of force and energy" but, even that doesn't happen. You use the magnet to pick up iron filings and then pick up more and the magnet is still just as strong. In fact, a "keepper" across the poles of a horseshoe magnet help retain the magnet's strength. Of course, there are some forces and movements at work, such as moving the magnet into the pile of filings but, it doesn't explain the notion that the action doesn't affect the magnet.....or does it?

 

[crashsite]

The fraudulent nature of the artificial horizon.

You mean like arrows, darts, bullets etc.

Exactly. Why don't the vecor moments just cancel (like the unmagnetized material when the magnetic dipoles are randomly aligned)?

 

[Pommie]

You should do some reading about Maxwell, he realised that a magnetic field would cause a current which would cause a magnetic field which would cause a current etc.... As you say, close to perpetual motion type stuff.

He went on to calculate the speed this would happen and it happened at the speed of light. The confusing thing about this was that it implied that the speed of light was always a constant, which no one could understand until Einstein came along. The fact he calculated this 150 years ago is mind boggling.

Mike.

 

[crashsite]

Hot as fire...black as night...

The fact he calculated this 150 years ago is mind boggling.

Also, that he mades a darn nice cup of coffee...

But, seriously...

Ah, to heck with seriously..

 

[3iMaJ]

You should do some reading about Maxwell, he realised that a magnetic field would cause a current which would cause a magnetic field which would cause a current etc.... As you say, close to perpetual motion type stuff.

He went on to calculate the speed this would happen and it happened at the speed of light. The confusing thing about this was that it implied that the speed of light was always a constant, which no one could understand until Einstein came along. The fact he calculated this 150 years ago is mind boggling.

Mike.

Originally Maxwell didn't prove that time varying electric and magnetic fields were linked he simply appended the time varying componenets to the curl equations. The reason he did this is he wanted to use the equations to describe travelling waves.

It can easily be shown that its fine to do so by taking the divergence of the curl equations and showing they're self consistant. But at the time this caused quite an uprising in the EM community.