Why magnet attract only metal ?

  1. Mar 23, 2006 #1
    I want to know that why magnet attract only metal but not all thing . Since all thing are made up of atom, what make the metal so difference so that it can be attract by a magnet ?
  2. jcsd
  3. Mar 23, 2006 #2


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    Magnets don't only attract metals, they attract and repel many things, usually you don't notice in everyday life.

  4. Mar 24, 2006 #3
    What is mean by permeability?
  5. Mar 24, 2006 #4
    metals have little sectors in their structures that contain magnetic moments that can be attracted to or unattracted to a magnet depending on the polarization of the sectors relative to the magnet's polarization (opposites attract).

    In general, compounds that are conductors (like metals) are easily magnetized, while compounds that are insulators (like plastics, glasses, woods) are difficult to magnetize. Although this is just a guideline and not absolute.
    Last edited: Mar 24, 2006
  6. Mar 24, 2006 #5
    This is all dead wrong. Since when are free charges attracted to magnets?

    Please refrain from "explaining" subjects which you know nothing about.
  7. Mar 24, 2006 #6

    When you have an individual electron, it behaves like a bar magnet (it has an intrinsic magnetic dipole moment). Usually electrons prefer* to pair up with another electron with the magnet pointing the other way - so the pair of electrons together has no magnetic dipole, they effectively neutralize each other (*this is because of the quantum mechanical principle of Pauli exclusion). In many atoms you have only such pairs of electrons, so the whole atom has no magnetic dipole. But for example, if there are an odd number of electrons* (example Alumnium, 13 electrons), there is at least one 'unpaired' electron, at the whole atom will have the magnetic dipole of this one electron; the whole atom will act as a bar magnet and respond to external magnetic fields. This is an example of paramagnetism.
    *this is not necessary but common

    This is a very weak effect - aluminum is attracted to magnets, but only slightly. When you deal with everyday magnetic materials, such as iron, a far stronger effect is involved.

    Instead of one atom acting individually as a little bar magnet, occasionally you have millions of atoms deciding to align with each other and reinforce each others' magnet dipoles - a magnetic domain. These are basically much bigger bar magnets, and are responsible for the strong magnetizibility of ferromagnets like iron. This can happen (the magnetic domains) if certain criteria regarding the solid's structure and bond lengths are satisified.
    Last edited: Mar 24, 2006
  8. Mar 24, 2006 #7
    It basically just tells you how a material responds to a magnetic field.

    If you apply a magnetic field to an object, any magnetic atoms inside will respond to it and move to a new configuration, possibly causing a new magnetic field of their own, distinct from the field you're applying. If the permeability is a large number, it gets magnetized parallel to the external field, and there is attraction. If the permeability is small enough, it actually magnetizes opposite to the external field (diamagnetism) and is repelled; this is a very weak effect and can be observed with pure water.

    see also http://en.wikipedia.org/wiki/Permeability_(electromagnetism)
    Last edited: Mar 24, 2006
  9. Mar 24, 2006 #8

    Aren't surface charges more likely to be attracted to magnets then volume charges inside the object?
    Are you refuting my whole post or just a piece of it?
  10. Mar 24, 2006 #9
    Charges aren't attracted to magnets, period.

    "Metals have little sectors" - most don't have long-distance ordering in the form of magnetic domains, only ferromagnets do (iron, cobalt, etc.).

    "magnet's polarization" - magnets are not generally polarized.

    "In general, compounds that are conductors (like metals) are easily magnetized, while..." - is not, 'in general'. There's no reason to expect it to be - the physics of ferromagnetism has nothing to do with conduction. Look at this short list of ferromagnetic materials - you have both very conductive metals and very insulating metal oxides.
    Another fallacy with this 'rule' - all the non-magnetic examples you've listed are amorphous, they do not have a regular crystalline structure and cannot be expected to be ferromagnets. An example of insulating non-metal ferromagnet would be carbon - in its novel nanofoam allotrope.
    Last edited: Mar 24, 2006
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