# Permanant Magnet Lines & Currents: [duplicate]

A permanent magnet produces lines of magnet flux that we call a "magnetic field". Those lines come from inside the magnet, come out of the N pole, loop outside the magnet, & return back into the S pole to complete a magnetic circuit. Using ferromagnetic materials, other magnets, &/or test equipment, we feel & measure forces that are caused by a magnet/s when other materials are placed within close enough proximity to the magnet/s (i.e. within their magnetic field/s). We therefore conclude that the magnetic lines flow in a specific direction & exert definite forces (i.e. magnitudes/strength) on some materials (ferromagnetic & other magnets), depending on where those materials are placed within the magnetic field of a magnet/s.

We label those forces as "H Field" & "B Field".
We measure H in terms of Amperes/meter. We measure B in terms of Newtons/meter/Ampere (or Tesla). We also commonly defined B in terms of the force that it exerts on moving electric charges (i.e. the Lorentz force).

An "Ampere" is basic unit of electrical current in the SI system, which = 1 Coulomb per second--which is formally defined to be the constant current which if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed one meter apart in vacuum, would produce between these conductors a force equal to 2 × 10 −7 newton per meter of length.

A "Coulomb" is the standard unit of quantity of electricity in the SI system, which = the quantity of charge transferred across a conductor in which there is a constant current of 1 Ampere/Second.

Consequently, those "magnetic lines" are currents (or flows) of charges that don't appear to need any external source of energy to continue generating their currents.

We also know those magnetic lines exist inside a vacuum, so they are independent of air molecules to flow outside of a magnet.

So now my questions:

1. Exactly what charged particles are flowing outside (and inside) a permanent magnet that create the magnetic "lines"?

2. Do those particles come from something inside the magnet or does the magnet do something outside of it to affect unknown particles to make the lines?

3. If there is a current (i.e. a continuous flow of charged particles), then why don't we harness that current like a water wheel (instead of 'using energy' to rapidly move copper wires through magnetic fields--like we do with electricity generators?) Shouldn't we be able to get the line currents to charge a capacitor (or or other device) & then later discharge the capacitor for the energy that we want?

• But your main misconception seems to be that field lines indicate flow of particles. This is not correct. Electric field occurs around charged particles but it does not contain or consist of particles. Magnetic field similarly doesn't consist of moving particles. For that matter, no "magentic particle" (aka magnetic monopole) has ever been observed, and so magnetic fields typically have their origin from electric currents or ferromagnetic materials whose microscopic structure produces magnetic dipoles. – The Photon Dec 25 '15 at 0:25
• @The Photon - I posted it in the Physics SE & here also, because of my last question. – zeffur Dec 25 '15 at 1:13
• Yes, the field lines exist. No, it is not a current. – The Photon Dec 25 '15 at 1:26
• @The Photon - the magnetic lines exist. They are currents that have direction (i.e. they flow from the N pole to the S pole) & they have magnitude/strength. If the lines do not consist of charged particles, then what particles do they consist of in your best gu/es(s)timation? re: "...magnetic fields typically have their origin from electric currents or ferromagnetic materials whose microscopic structure produces magnetic dipoles." What particles does the magnetic energy that is flowing in a directional current outside of the magnet consist of? – zeffur Dec 25 '15 at 1:28
• @The Photon - How is it not a current if we measure the B field in Newtons/meter/Ampere (or Tesla) & H fields in Amperes/meter? Both Ampere & Coulomb refer to currents. – zeffur Dec 25 '15 at 1:30

Exactly what charged particles are flowing outside (and inside) a permanent magnet that create the magnetic "lines"?

The magnetic field of a permanent magnet is not caused by flowing particles.

The electrons within a ferromagnetic material, even if they aren't flowing, have quantum mechanical spin. If the spin vectors of many of the electrons within the material are aligned, they produce a net magnetic dipole moment, producing the macroscopic magnetic field lines associated with a permanent magnet.

(This is just another way of saying, even when electrons aren't moving, they produce a magnetic field. We don't really know "why" that is, but we have a mathematical model of how much field they produce and how it interacts with other objects, and we call that model the "spin" of the electron).

Do those particles come from something inside the magnet or does the magnet do something outside of it to affect unknown particles to make the lines?

It comes from the electrons in the magnetic material.

If there is a current (i.e. a continuous flow of charged particles), then why don't we harness that current like a water wheel

Since the magnetic field doesn't derive from the flow of particles, we can't harvest it as if it were a flow of particles.

We measure B in terms of Newtons/meter/Ampere ... Consequently, those "magnetic lines" are currents (or flows) of charges

The B-field has amperes in its units because it produces a force on a moving charge according to the Lorentz law:

$$\vec{F}=q\vec{v}\times{}\vec{B}$$

Since it is multiplied by a charge and a velocity to produce a force, it must have units $\dfrac{[\mathrm{N}][\mathrm{s}]}{[\mathrm{C}][\mathrm{m}]}$ in order for the equation to balance.

Just as a force itself has $[\mathrm{kg}]$ in its units because it has an effect on something with mass, although a force does not have mass itself; a B-field must have charge in its units because it effects charges, not because it is composed of charge or contains charge.

• A permanent magnet has mass & it's magnetic lines create forces that cause those lines to complete a magnetic circuit & to affect ferromagnetic materials that are within its field. Clearly magnetic force is moving mass in that example. Based on the definitions of the B & H fields, I think we can reasonable conclude the lines are currents with 'something' flowing through the magnetic circuit--what is that something?? – zeffur Dec 25 '15 at 1:55
• re: "The B-field has amperes in its units because it produces a force on a moving charge according to the Lorentz law"-- or is it that a moving mass of charged particles (e.g. a copper wire) produces a force (Voltage) when it is moved repeatedly past a magnetic B field? – zeffur Dec 25 '15 at 2:18
• @zeffur, same thing. The force wouldn't exist if the B-field weren't there. – The Photon Dec 25 '15 at 2:25
• re: "If the spin vectors of many of the electrons within the material are aligned, they produce a net magnetic dipole moment, producing the macroscopic magnetic field lines associated with a permanent magnet." The definition of a dipole is "a pair of electric point charges or magnetic poles of equal magnitude and opposite signs, separated by an infinitesimal distance." A strong permanent magnet has quite a lot larger dipole distance than the dipole definition shows. – zeffur Dec 25 '15 at 2:29
• Also, I still don't see how directional flux lines exist without energy or something flowing in a magnetic circuit. Do we not have a word for whatever is flowing to create the magnetic field & directional current? – zeffur Dec 25 '15 at 2:29