Do all moving charges create a magnetic field?

[ZenBeam]

@MikeS

I (and assumedly Chronos) thought you were talking about the ratio of gravitomagnetic to gravitoelectric forces. And roughly speaking, the ratio of gravitomagnetic forces to gravitoelectric forces is of the same order of magnitude as the ratio of magnetic to electric forces. (In fact, the gravitomagnetic:gravitoelectric ratio is four times larger than the magnetic:electric ratio in an analogous situation.) Take a gander at the equations here. But if you’re comparing gravitomagnetic forces to magnetic forces instead, then yes, they’ll be much much smaller.

Looking at those GEM equations makes me wonder: Could there be (or are there) intrinsic gravitomagnetic dipoles, analogous to fermions having an intrinsic magnetic moment? Or is it just the regular fermion spin?

[MikeS]

@ZenBeam

Looking at those GEM equations makes me wonder: Could there be (or are there) intrinsic gravitomagnetic dipoles, analogous to fermions having an intrinsic magnetic moment? Or is it just the regular fermion spin?

A “gravitomagnetic dipole moment” is just angular momentum, so since plain old fermions have intrinsic angular momentum, they have an intrinsic gravitomagnetic dipole moment. (Probably — the caveat here is that nobody’s quite sure how gravity works on a quantum level, and the intrinsic angular momentum of particles is inherently a quantum phenomenon.)

[KarlGauss]

The question in the OP was answered in the affiirmative - all moving charges create a magnetic field. This makes me want to ask the following, probably silly, question:

On the scale of, say, the radius of a proton, do quarks create a magnetic field as they dance about with their partner(s)? (I know they can never be free, but I am wondering about quarks within hadrons - is there any hint of ‘subhadronic’ magnetic fields therein? What would a magnetic field generated by a fractional charge look like?)

[Chronos]

Well, protons do have magnetic moment, and you could interpret that as being (partly) due to the quarks dancing around, but at that level, you’ve got to be very careful about defining what you mean by “motion”.

[Kevbo]

@billfish678

Not only do electrons not go the speed of light, they often go pretty damn slow. I recall an old physics homework problem where we calculated the speed of electrons moving through a wire. IIRC it was on the order of a few feet per second.

The wire will burn up if they move that fast. They move closer to the speed of the minute hand of a clock than the second hand.

Yes all moving charge generates a magnetic field. There is a rather famous demonstration using the hall effect to distinguish the polarity of the charge carriers in a semiconductor. You can determine that the charge in a “P” type material is carried by positive charges (holes) rather than electrons.

[purplesparks]

A magnetic field is an effect. It is the flow of whatever is causing the mass to be charged. When the mass is static the magnetic field disappears because it is an effect, When it moves the flow supporting the charge of the mass is altered and the field lines become apparent. The magnetic flow is still there though even when the particle is at rest. Hmmm. Where does it go and where does it come from. ?