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Will a magnetic field pass through non magnetic materials

  1. Jan 25, 2012 #1
    Hi and thanks for helping me with these physics questions.

    Firstly, will a magnetic field pass through non magnetic materials as though it was air? For example, will a magnet still attract another magnet when copper or wood is placed in between it?
    I understand that if the material in between it is a magnetic material then magnetic shielding will occur. however, I'm not very sure if the magnetic field will simply pass through non magnetic materials as though it was air?

    I think that it should be able to pass through them as long as the magnetic field is strong enough.

    Pls help me with this question. thanks so much for the help
  2. jcsd
  3. Jan 25, 2012 #2


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    A magnetic field (of any size) will simply pass through a non magnetic material as though it were air?
  4. Jan 25, 2012 #3


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    Air is a non magnetic material.
  5. Jan 25, 2012 #4
  6. Jan 25, 2012 #5
  7. Jan 25, 2012 #6
    Oh I read the article on Wikipedia. So since copper n lead (most non magnetic materials) have a portability of 1, then putting a piece of copper will have no effect at all? But when wood is placed in between a magnet n a magnet, it can attract less iron nails than when the magnet is directly exposed to the iron nails.
    So I'm not very clear on this part.
  8. Jan 25, 2012 #7
    Things like air aren't the same as a vacuum to a magnetic field. In general ANYTHING, ferromagnetic or otherwise, is made of atoms and in magnetic fields the electron orbitals of atoms actually distort even if the atom normally is non-magnetic. The two main effects are a component which tends to align with the external magnetic field (this is called paramagnetism), and an effect that tends to cancel out the external magnetic field (diamagnetism). In a lot of materials the paramagnetism dominates (it depends on the total angular momentum of the atom) but in some diamagnetism does. Anyway, my main point is that the magnetic field tends to induce a magnetic field (which either may work with or against the external field) in non-magnetic materials. Thus, no, air is not "invisible" to magnetic fields.
  9. Jan 25, 2012 #8
    Oh so does this mean that magnetic fields will pass through materials the same way if they have the same portability? Like air n copper n most non magnetic materials? Since they all have the same portability? Meaning 1com of air n one cm of wood or copper won't change the no of attracted pins for example?
  10. Jan 25, 2012 #9
    Yes it is right i read something like this too..but what i had in mind was this-any non-magnetic substance kept in the vicinity of a magnetic field will strangely have it's atoms aligned in such a way that a magnetism is induced in it which may be temporary or permanent depending on the retentivity power.However what you said about diamagnetism confuses me..If you could elaborate a bit more here-the factor on which magnetism inducing or opposing depends..and do all matter always have to have some change or the other when placed in a magnetic field?
  11. Jan 25, 2012 #10
    Another thing- an induced cobalt and a bar magnet basically differ in only 1 thing-the latter has poles while the former does not..is it true?
  12. Jan 25, 2012 #11


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    I repeat:
  13. Jan 26, 2012 #12
    Yes all matter interacts with magnetic fields, it's a basic property of atoms. As for elaborating on what diamagnetism is I don't know if I really can, diamagnetism, just like ferromagnetism (permanent magnets) is ultimately and entirely quantum mechanical effect, if you don't know quantum mechanics there's not much headway to be made. However, I can say that though technically all atoms have paramagnetic and diamagnetic interactions it's only atoms with un-filled electron shells that have any appreciable magnetic properties. In addition to this the paramagnetism aspect is in general much stronger than the diamagnetic so it's dominant. The exception to this is certain atoms where the paramagnetic interactions vanish (again the reasons are quantum mechanical). In these materials, even though the diamagnetic interactions are just as weak as other atoms, diamagnetism is the dominant effect.
  14. Jan 26, 2012 #13
    Oh ok thanks for the help. I understand it now. Then when magnetic shielding happens, if a long n thin strip of iron is placed between a magnet and some pins then the pins won't get attracted? It's because no magnetic field lines pass through them right? Even though there are 2 south poles in the middle of the magnet facing the pins. But then if it was free to move it would get attracted as the field lineage pass through it rigght? Even though its only the 2 south pole facing which is similar to the pins case? So does it mean that the object will only move if a magnetic field is present despite if the poles are at present?

    So in conclusion the only way for an object to be attracted is if
    1) the object must be within the magnetic field of a magnet
    2) the object must have their poles (doesn't matter how it gets it even induction is considered)

    Am I right to say this? Thanks for all the response and help!
  15. Jan 27, 2012 #14
    I have not read quantum mechanics yet so i am not going to trouble you any more!
    Anyways thanks for the support
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