Magnet Myths and Misconceptions

[TinselKoala]

Charge. It is the motion of charge, not of electrons themselves, that makes the field.

Electrons carry the unit negative charge, by definition and measurement, but as Qwert points out above the electrons themselves, for example in metal wires, don't need to move that fast. I think the situation with charge and moving electrons is kind of like "Newton's balls", where units of charge (the momentum of the "input ball") are transferred across the system very rapidly, even though the individual "balls" don't move hardly at all.
Magnetic fields can be produced by moving ions, both positive and negative. So it is the motion of the charge, not the motion of the charge +carriers+, that produces the field. Charge, motion, field: One thing. One.

OK, carry on.

[Liberty]

Charge. It is the motion of charge, not of electrons themselves, that makes the field.

Electrons carry the unit negative charge, by definition and measurement, but as Qwert points out above the electrons themselves, for example in metal wires, don't need to move that fast. I think the situation with charge and moving electrons is kind of like "Newton's balls", where units of charge (the momentum of the "input ball") are transferred across the system very rapidly, even though the individual "balls" don't move hardly at all.
Magnetic fields can be produced by moving ions, both positive and negative. So it is the motion of the charge, not the motion of the charge +carriers+, that produces the field. Charge, motion, field: One thing. One.

OK, carry on.

So the movement of many charges (ions) in a magnet is what produces the continual magnetic field in a magnet?  Why can't these charges be depleted?

Liberty

[MileHigh]

Newton II:

Yes, we agree that a moving electron has a magnetic field that "moves" with it.  Note however that I put "moves" in quotations.  The magnetic field does not literally move with the the electron.  What really happens is the moving electron changes the local magnetic field at every point in space around the moving electron as it moves.  In other words, if you are at a fixed point in space and an electron moves past you, you experience a changing magnetic field.   It's a subtle but important difference.

Think of sound waves.  A police car drives past you with the siren on.  You hear the siren first low, then very loud, and then low again.   The sound changes in volume as the police car passes you, but the sound is not literally "moving" with the police car.  The police car siren is emitting a fixed unmoving sound at every instant in time.  This is a continuous process.  Think of a boat moving through the water as another example.  The moving electron causes a "local disturbance" in the magnetic field.

When the moving electrons stop the energy contained in the magnetic field has to go somewhere.  In most cases the electrons move past the "stop point" because of the electrical inertia associated with the whole process.  That's the high-voltage spike.  It does not necessarily mean that the energy will become an EM wave.

In mechanics a solid mass 'm'  moving with velocity 'v' develops  kinetic energy  of  ½ mv2.   But when you supply energy to the electrons by applying voltage, the electron  cannot store energy in the form of   ½ mv2  because its mass is negligible.  So it creates a magnetic field to store the supplied energy.   When electrons are stopped, energy is released as EM wave.

There is a direct correspondence.  Mechanical inertia is mass x velocity.  Electrical inertia is inductance x current flow.  So for an inductor with current flowing through it, the magnetic flux generated is effectively the electrical inertia.  Think of this:  You energize an inductor and put energy into it by applying (voltage x current x time).  That creates a magnetic field.  The current flow and the magnetic field are directly related to each other  (current flow -> magnetic field).  So if you try to stop the current flow then the magnetic field "takes over" to induce the current flow (magnetic filed -> current flow.)  They are so closely related that one becomes the other and vice-versa.

TK:

There are a lot of misunderstandings about electric fields and charge also.  In a generator, there is no "charge" in the wires.  There is an induced electric field that pushes the electrons through the wires, without any net charge in the wires themselves.  Likewise, some people talk about voltage being related to charge density, but that's only for static electricity.  You have voltage in the windings of a generator with no excess charge density.  There are two sources of an electric field, the static electric field associated with electrostatics, and the "dynamic" electric field associated with changing magnetic fields.  A so-so analogy for current flow in a wire because of a dynamically induced electric field might be a simple vertical shaft with balls falling through a gravity field.  The gravity field is like the electric field and the balls are like the electrons.

Liberty:

The source of the magnetic field in a magnet is the trillions and trillions of electrons orbiting iron atoms where they are all orbiting in the same rotational direction.  Each one acts like a little tiny magnet.  The electrons spinning in tight little circles still create a magnetic field in the same way that an electron creates a magnetic field when moving in a straight line.

MileHigh

[Pirate88179]

I have a question.  If you have a piece of 12ga. copper wire that has been used in operation with heavy currents (not over the wire's rated capacity though) for say 50 years.  If you take a new piece of the same ga. wire and compare the two...is there any differences that can be observed from the years of electron "movement" or "vibrations" in the old wire vs. the new?  In other words, and I am not talking about the elements degrading the insulation, or anything associated with over heating of the old wire, is there any chemical or physical change in the wire, like density, or any other change as a result of the electron movement in it for all of those years?

I have heard electricians use the term that an old wire was "worn out" and he was not talking about the insulation as it was bare copper wire.  What does this mean?  And, is it a result of electron movement causing degradation of the molecules in the copper wire?  Or, under a powerful electron microscope, would we see no changes in the old, used wire vs the new wire?  Does the old wire's resistance increase somehow over time and the resulting heating cause this degradation?  If so, what changes occur in the wire to cause it's resistance to increase?

Thanks, I am learning a lot in this topic thus far.

Bill

[Newton II]

Why can't these charges be depleted?
Liberty

I think that is a great question.

In mechanics, the kinetic energy of a moving mass is defined as  "energy possessed by virtue of its velocity" and its magnitude is 1/2mv2

And potential energy of same mass is defined as "energy possessed by virtue of its position" and its magnitude is 'mgh'  where 'h' is its height above the ground. (reference)

So, when magnetic field produced by a moving charge is analogous to kinectic energy,  the static charge should be analogous to potential energy.

A  moving charge looses its kinetic energy which is magnetic field, when the charge is stopped. But it will still have potential energy in the form of electric charge.  This potential energy will be lost only if this charge literally 'falls' on the reference which is responsible for imparting potential energy on it.

The question here is,  a charge possesses potential energy with reference to what?  and who imparts it potential energy by  'lifting'  it above the reference?

I think this question is being dealt with in quantum mechanics since the very birth of quantum mechanics.  Don't know whether 'quantum mechanists'  have got the answer yet.

If this question is answered we will know the secret of this universe.

And it will be a revelation of 100G where 'G' stands for God.