Can a magnetic fields/forces do work on a current carrying wire?!

Miyz

What do you mean by the SNF? &"important to emphasize that the currents in the field & armature windings (rotor & stator if you prefer), control the value of magnetic force, which results in electric & SNF matching the mag force."
Could you clarify this a bit more(Simpler way), I do understand the "tethered" part. But not sure what you're talking about hee...

Hence the idea of opposing and attracting magnetic fields.
E forces... Whats SN forces?

I thought by applying the magnetic force on the electron directly, an indirect force is applied on the proton and neutron?

Miyz

I guess we truly need to breakdown things to the quantum level to understand how energy,force,work is all processed in this system. Interesting topic.

cabraham

The tethering was explained in the link I referred to, from a thread in 2009. If you review the link then I will clarify if needed. SNF is the "strong nuclear force", which tethers the neutron & proton together. I brought it up simply because some suggest that the "E forces" are "really doing the work". I just wanted to remind all that an E field cannot move a neutron. The neutrons are roughly half the mass of any element/compound, except those with hydrogen. So neutron forces/motion cannot be explained with B or E forces, only SNF.

Have I helped? BR.

Claude

Miyz

Claude, Based on what you said and Darwin123. Is it safe to say: Magnetic field's can do work under certain circumstances? ONLY in the presence of both E forces + N forces can magnetic fields do work.

In a sense they are... So as E force, So as the N force.

They all were triggered in this even or "action" to do work. I would say this in a general simpler way:

Magnetic force can do work with the presence of E,force + N,force.
Electric force can do work with the presence of M,force + N,force.
N force can do work with the presence of M,force + E,force.

In a sense the motor effect... A simple effect CAN NEVER occur without the upper 3 rules.
They are all dependent on each other. without one of them. Nothing would happen.

Simple forces added up together to give the total work.

cabraham

That sounds pretty reasonable to me. Several of us examined this exhaustively, & collectively we ascertained what you just said. Ultimately, though, I believe that the actual work is done by the power source driving the motor. Although energy can be stored in fields, then released to another entity, it is the power source, i.e. the wall outlet power mains, that is providing ALL the energy/power.

In a motor, of course all 3 forces work in unison, but it is safe to say that the magnetic forces, i.e. B/H, are the quantities that literally control the motor action. SNF & E tag along like an obedient shadow, but magnetic is in charge. Using my 3 ball analogy, a magnet lifts 3 tethered balls, steel, wood, & rubber. The magnet cannot lift wood and/or rubber, but it lifts them indirectly by lifting the steel ball directly, & relying on the E & SN tether forces to lift the rubber & wood balls.

But let us not forget, the magnet must provide a lifting force equal to the combined weight of all 3 balls. If each ball weighs a pound force, then the mag force must be 3 lbf. But the E & SN forces are only equal to the weight they carry. If the steel ball is on top, then E & SN provide 2 lbf, while the mag is 3 lbf. So the magnetic force is definitely the prime mover but it still relies on help from E & SN.

Interesting question. These puzzles get us thinking. I want to thank everybody here for being polite. These types of questions usually end up in a mud wrestling match. Everybody on this thread conducted themselves very well, & I take my hat off to all. I hope future discussions can be this civil. Best regards.

Claude

Darwin123

And gravitational forces. Let us not forget those! Furthermore, you have to say what it does work on. I think that you are asking whether a magnetic field can do work on an electric charge or electric current.
I think the following is valid, but demonstrating it may sometimes be difficult.
ONLY in the presence of both E forces + N forces+gravitational forces can magnetic fields do work on an electric charge or electric current.

cabraham

Other than gravity, we seem to have reached a unanimous agreement. But gravity is too weak to be concerned with as it is many orders of magnitude smaller than E, M, or N. Nonetheless, we cannot deny its presence, nor that of "W" (weak force", if such materials are present, but I don't think beta decay is present in motor materials).

Thanks again to all. BR.

Claude

Miyz

When you break that down you'd realize that what the energy source is really just supplying the E forces within a distance. Already energy has been transfered on the wire, and work has been done.

I believe then the E force + SN force would interact with the M forces. We all should break down the concept of Work in, and Work out. Its more understanding when you would say the Forces in and the Netforce out. If you see where I'm going with this... It simply draws a better picture you can visualize it and understand everything more clearly then saying energy In and the energy converted(With respect to all laws, thats just my own way of understanding the relationship of energy,work,force all together).

Thanks! We should raise questions similar to this! To understand the truth about it more!

Miyz

Thank you all again for you're efforts!

chingel

It is important to note that magnetic fields apply forces only on moving charged particles, and for example in the the case of the electric motor, not on the wire itself but on the electrons.

I found this picture from google:



Consider a stationary particle that is on the path of the moving charged particle after it has moved through the magnetic field (for example where the arrow points that is with the text "Path of the particle"). The charged particle would collide with the stationary one after having gone through the magnetic field. Note that the magnetic field does no work on the charged particle, gives it no additional kinetic energy, only changes its direction. If there were no magnetic field, the particles wouldn't collide, but the magnetic field makes them collide and "makes" the second particle move. So it would seem that the magnetic field did work on the other particle, but it didn't, it simply redirected the first particle to hit something it otherwise wouldn't.

The energy to do the work came from the kinetic energy of the first particle, yet without the magnetic field the work couldn't not have been done on the other particle. Nevertheless, the magnetic field did no work, it simply redirected a particle's path.

In the case of the electric motor, the magnetic field would also simply change the paths of electrons, but would not give them any additional energy. The kinetic energy for the moving wire would come from the kinetic energy the electrons had before.

Miyz

Um, if you say that magnets do no work... Check this out

1 - Yes they can,
2 - Why?
3 - Convinced?

If you still need some more "worded" detail check theses links out: 1, 2,

As I said before and I will say this again. Magnets/magnetic fields/etc... Are not understood fairly well... I mean so many attention went for complex idea how the most simplest products of nature and most important forces have been underrated....

cabraham

But we're discussing forces between current carrying wires, akin to motor operation. We're not discussing collisions among particles. It has already been stated unanimously that a single charged particle, or several, moving through a magnetic field can only have its momentun changed, not its kinetic energy.

The rebuttal directly before this one by Miyz addresses what we've been talking about. When 2 current loops interact resulting in a net torque, we are examining the work done, forces involved, etc. Please review the link I gave earlier. Rather than repeat what has already been discussed, I will elaborate if you still have questions. Best regards.

Claude

Miyz

He should review you're thread and ours. Then he would understand our common conclusion about magnets doing work or not.(Again, THEY DO but UNDER CERTAIN circumstances)

chingel

A current through a wire is several charged particles moving. They feel the magnetic force, not the wire directly, and respond to the force by changing their direction and giving some of their momentum in the new direction to the wire, creating a force on the wire.

It should be similar to the collision. The direction of the electrons is changed and thus allowing them to do work on the wire by colliding with it. Otherwise the collisions would be chaotic, but the magnetic force changes the directions of the electrons in a consistent manner and allows the work to be done at the expense of the electrons kinetic energy, as in the case of a simple collision.

Darwin123

Another assumption implicit in your diagram is that the permanent magnets don't move. This is one reason the magnetic field is static. If the magnets were allowed to move, then the problem would be more complicated.
The magnets keep their shape by rigid body forces. They may be held stationary on the horizontal plane also by rigid body forces. For instance, the mangets may be attached by glue to the horizontal surface. However, suppose the magnets are not attached directly to the plane.
If the magnets are not attached directly to the surface, then there has to be other forces involved. The magnets may have to be held still by a mixture of both gravity, contact force and static friction. The gravity prevents the magnet from moving up. The contact force (i.e., the normal force) prevents the magnet from sinking down. The static friction prevents it from moving in the horizontal plane.
Similarly, the wire loop has some weight. If the wire loop is not uniform in thickness, the unbalanced wire could be affected by gravity.
The weight of a single carrier may be negligible. However, the weight of other components in the system may not be negligible.
The discussion has turned to the contribution of nonmagnetic forces to the work done on the wire loop. The conjecture has been raised that maybe nonmagnetic forces "do work" in a motor. Gravity may well "do work" on a motor.
Fortunately, the problem can be solved without enumerating all the forces "that do work". The work done by most of those forces cancel out. By choosing the boundaries on the system properly, one can "hide" the forces that cancel out. In general, this is what has to be done.

cabraham

An internal collision does not do work on the wire since conservation of momentum requires that the wire moves, i.e. undergo a momentum change, only when acted upon by an external force. This force is M. But, M exerts no force on stationary lattice protons & neutrons. Hence E & SN forces provide the tether force so that when M yanks on the electrons, the protons & neutrons are tethered along by E & SN forces.

Claude

cabraham

How can gravity "do work" on a motor? I just want to know how.

Claude