Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Does everything have a magnetic field.

  1. Oct 22, 2005 #1
    erm i kno this has nothing to to with the original topic, but i didn't want to start a new thread..does everything have a magnetic field ? or only certain materials ones that have magnetic properties or currents..etc
    (this probably is a silly question)
    Last edited: Oct 22, 2005
  2. jcsd
  3. Oct 24, 2005 #2
    Moving charges create a magnetic field around themselves. Considering the fact that electrons are 'moving' around the nucles (Not a complete picture of how it 'really' works, really), everything should have a magnetic field. However, the field ought to be too small to detect.

    Does everything have magnetic a field? :uhh:
  4. Oct 24, 2005 #3

    Claude Bile

    User Avatar
    Science Advisor

    To Stalefish: Atoms possess magnetic dipoles, yes. This is well covered in standard atomic theory. Neutral particles, for example, neutrons do not possess a magnetic field.

    To alias25: The interaction between atomic dipoles determines the magnetic properties of a bulk material.

  5. Oct 24, 2005 #4


    User Avatar
    Science Advisor

    Neutrons ARE magnetic: a particle neddn't be charged to have a magnetic moment. So in a sense, every material thing, being composed of particles with magnetic moments, is magnetic. However, in most cases, these moments are in all directions, and so the magnetic field of these materials cancels out if you are on a scale large compared with particle separation. The exception is ferromagnetic materials such as nickel and iron, whose atoms have net magnetic moments and in the solid state these atoms like to have their moments pointing in the same direction.
  6. Oct 25, 2005 #5

    Claude Bile

    User Avatar
    Science Advisor

    In a thread a while back, it was said that neutrons could not be confined in a magnetic field (via their neutrality? I can't remember what the reason was). Now that I think about it, neutrons, are themselves made of charged particles, so they ought to possess an intrinsic magnetic field, for much the same reason that, while some atoms are neutral overall, they still possess a magnetic dipole moment.

  7. Oct 26, 2005 #6
    Well, the magnetic moment is due to the spin of the neutron, rather than its constituents.
  8. Oct 26, 2005 #7

    Claude Bile

    User Avatar
    Science Advisor

    I will defer to Krab and Lonewolf on this.

  9. Oct 29, 2005 #8


    User Avatar
    Homework Helper

    If you treat the neutron as a "point object", it has zero charge.

    If you treat the neutron as an extended single item,
    it has NONzero charge density throughout
    (as I recall : negative inside, positive near the outside)
    but zero total charge.
    "spin" of the charge density leads to magnetic moment.

    If you treat the neutron as composed of 3 quarks,
    each one has charge and orbital angular momentum,
    as well as (probably) magnetic moment due to "spin".

    In no case does there seem to be a need
    to ascribe the magnetic field
    to anything other than moving charge
    - except for the unrealistic model of a "point" object.
  10. Oct 29, 2005 #9
    Those particals are too small to understand, maybe they are huge compare with their sub particals, who says there is no such thing? Just too small to detect yet. Maybe.
  11. Oct 29, 2005 #10
    Electrons are, according to our current understanding, fundamental particles (Leptons). Protons and Neutrons are made up of smaller particles called quarks.
  12. Oct 30, 2005 #11
    This is a quite different matter. Charged particles ( such as protons and electrons ) can be contained in a magnetic field because of the electromagnetic force they experience while travelling through the field. In general any charge q traveling through a magnetic field B with velocity v will experience a force according to the equation:

    F = q v x B

    Where x stands for the cross product. In the case that you have not heard of a cross product, all you really need to know is that the magnitude of the force will be :

    F = q v B sin ( theta )

    Where theta is the angle between the particle's trajectory and the magnetic field. This force will be in a direction perpendicular to both the magnetic field and the particle's trajectory.

    Neutral particles ( such as neutrons ) have 0 charge, so the force they experience will be just:

    F = 0 * v * B * sin ( theta ) = 0

    For this reason it is fairly difficult to capture neutrons in a magnetic field. Whereas electrons and protons experience rather strong electromagnetic forces due to their electric charge while traveling through a magnetic field, neutrons experience only a weak force that is due to their magnetic dipole moment.
  13. Oct 30, 2005 #12

    Claude Bile

    User Avatar
    Science Advisor

    Just because something experiences a force, doesn't mean it can be confined by the force, for example, one cannot confine a charged particle, electrostatically, despite the fact that one can exert an electrostatic force.

    Thankyou though for that demonstration, though my knowledge of physics does extend a little past high school level.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook