Magnetic field

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what is magnetic field and ? how it forms ?
 

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  • #2
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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.
 
  • #3
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can you Explain? more and what you mean by frame ?
 
  • #4
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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.
 
  • #5
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that's better is the earth charged mass?
 
  • #6
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Earth is mostly a neutral mass.
 
  • #7
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and what about sun ? charged ?
 
  • #8
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Mostly neutral too.
 
  • #9
tiny-tim
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welcome to pf!

hisciboudy! welcome to pf! :smile:
what is magnetic field and ? how it forms ?
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:
 
  • #10
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thank you every one for helping me need more to know Equations
it will be good
 
  • #11
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and i want know difference between magnetic field intensity and magnetic flux
 
  • #12
tiny-tim
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hi sciboudy! :smile:
and i want know difference between magnetic field intensity and magnetic flux
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
 
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  • #13
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what is magnetic field and ? how it forms ?
A magnetic field is the same as electric forces. They are unified under relativity. It is formed by particles moving in an electromagnetic field.
 
  • #14
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hi tiny
i'm sorry i still understand the difference between H and B
and M :cry: :cry:
 
  • #15
Born2bwire
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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).
 
  • #16
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: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
 
  • #17
tiny-tim
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  • #18
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: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:
 
  • #19
tiny-tim
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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
 
  • #20
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thank you very much:smile:
 
  • #21
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I like to think of H as the original magnetic field, what would exist if there were no materials, and B the magnetic field due to the original magnetic field and magnetization of materials.
 
  • #22
Drakkith
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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.
Is it purely a relativistic side effect? If so, I don't see how charges could ever produce a magnetic field that would attract other like charges without being in a material such as a conductor. For example when you accelerate a beam of protons.
 

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