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Magnetic field

  1. Jun 19, 2011 #1
    what is magnetic field and ? how it forms ?
  2. jcsd
  3. Jun 19, 2011 #2
    When a charge is in a different frame than you are, you will observe a magnetic field. It is not there for all frames. It is a relativistic side effect.
  4. Jun 19, 2011 #3
    can you Explain? more and what you mean by frame ?
  5. Jun 19, 2011 #4
    When electric current flows (like the coils in a motor or transformer) it creates a magnetic field.

    But if you could take a ride with the electron as it moves, you would not see any magnetic field. You would only see the static electric field.

    This means different people measuring the electric and magnetic fields can measure different values for both just because of the way they are moving in relation to the charge.

    The way you are moving is called a "frame" by physicists.
  6. Jun 19, 2011 #5
    that's better is the earth charged mass?
  7. Jun 19, 2011 #6
    Earth is mostly a neutral mass.
  8. Jun 19, 2011 #7
    and what about sun ? charged ?
  9. Jun 19, 2011 #8
    Mostly neutral too.
  10. Jun 19, 2011 #9


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    welcome to pf!

    hisciboudy! welcome to pf! :smile:
    as you know, an electric field originates from electric charge

    however, there are no "magnetic charges" (you can't have an isolated magnetic north pole, for example), and instead a magnetic field originates from the movement of electric charge

    this movement is usually a circle, and the magnetic field is along the axis of the circle

    the magnetic field of an ordinary permanent magnet, for example, results from the circular orbits of electrons facing roughly parallel … so the electrons (which are moving charges) all produce tiny parallel magnetic fields which combine to make a big magnetic field :wink:
  11. Jun 19, 2011 #10
    thank you every one for helping me need more to know Equations
    it will be good
  12. Jun 19, 2011 #11
    and i want know difference between magnetic field intensity and magnetic flux
  13. Jun 20, 2011 #12


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    hi sciboudy! :smile:
    from http://en.wikipedia.org/wiki/Magnetic_field" [Broken] …
    Alternative names for the field B
    • Magnetic flux density
    • Magnetic induction
    • Magnetic field (rare outside physics)
    Alternative names for the field H
    • Magnetic field intensity
    • Magnetic field strength
    • Magnetic field
    • Magnetizing field

    B is the total magnetic field

    M, inside a material, is the magnetisation field (or dipole moment field), ie that part of B due to the dipole moments of the material

    H, inside a material, is what is left after we remove M from B0

    (so, in a vacuum, H is the same as B0)

    B field lines never end (they are either closed loops, or they go off to infinity at both ends)

    H and M field lines start and end at magnetic North and South poles​

    The total B flux through a closed surface is zero (because there are no "magnetic charges", or magnetic monopoles)

    The total H flux through a closed surface is minus the total M flux, and is the sum of the enclosed magnetic poles
    Last edited by a moderator: May 5, 2017
  14. Jun 20, 2011 #13
    A magnetic field is the same as electric forces. They are unified under relativity. It is formed by particles moving in an electromagnetic field.
  15. Jun 20, 2011 #14
    hi tiny
    i'm sorry i still understand the difference between H and B
    and M :cry: :cry:
  16. Jun 20, 2011 #15


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    When physicists talk about the magnetic field, they are talking about B. In the simplest of problems that is normally all we are discussing. However, materials behave differently when under the influence of an applied magnetic field (B). Materials can become magnetized. What happens is that the applied magnetic field (B) on a material induces magnetic dipole moments in the material. All these tiny induced dipole moments will add up to a secondary net magnetic field (M) called the magnetization.

    So, as Tiny Tim stated above which I am simply restating to sound smart and pad my postcount, B is the total magnetic field. M is the magnetization field and can be thought of as the distorting magnetic field produced by the induction of a magnetic dipole moments in a material. The H could be likened to what would have been the magnetic field due to the free and bound currents (as opposed to the induced moments).
  17. Jun 20, 2011 #16
    :smile:thank you every one
    that's better i need some lecture notes or good book in magnetization and it's be simplest
    because i'm not speak English well not my langue thank U ev
  18. Jun 20, 2011 #17


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    Last edited by a moderator: May 5, 2017
  19. Jun 20, 2011 #18
    :smile:thank you tiny very much very good web site but i donn't know how to download books from this site ? it will be perfect if you tell me?:bugeye:
  20. Jun 20, 2011 #19


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    click where it says "Url" (or in this case, just click the second link in my previous post) :smile:

    anything ending in ".pdf" is an Adobe Acrobat Reader file (if you don't have that software, you can download it free from the Adobe website) … the page comes up completely black at first, and you have to wait for it to load
  21. Jun 20, 2011 #20
    thank you very much:smile:
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