Electron spin? how?

  • #1
harjot singh
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how actually electron and protons spin? explain me whether this spinning could provide torque to the positive charges then it means electrons and protons keeps rotating under their electrostatic field?
 

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  • #2
ChrisVer
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electrons are fundamental particles until today, so you can't really see them as spinning balls in order to give them that spin. In fact it's impossible to give it to them that way, since it would need them to spin faster than the speed of light (you know their spins, you know their radius boundary, so you can calculate the corresponding speed v, to find v>c).
under EM field, the spin itself spins around the Magnetic field...(spin transition)
 
  • #3
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how actually electron and protons spin? explain me whether this spinning could provide torque to the positive charges then it means electrons and protons keeps rotating under their electrostatic field?

The electron doesn't spin in a Quantum Mechanical view but there is a component of its equation that resembles classical spin of an object and so its been named as such:

http://en.wikipedia.org/wiki/Spin_(physics [Broken])
 
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  • #4
jtbell
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how actually electron and protons spin?

They don't actually spin like a classical spinning ball, because they aren't actually little balls (or any other classical object). Nevertheless, they have "intrinsic angular momentum" which is a fundamental property like mass and charge. "Intrinsic angular momentum" is a mouthful to say all the time, so we say "spin" for short. This was probably an unfortunate choice because it confuses so many people. Nevertheless, this term is so deeply embedded in physics language that it's impossible to change now, so we have to live with it.
 
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  • #5
harjot singh
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so what causes magnetic dipole moment in a ferromagnets?
 
  • #7
harjot singh
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i just couldnt understand the language of wiki so could u please help me out!
 
  • #8
harjot singh
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how an electron cant have a spin because they have an angular momentum i.e spin angular momentum then why?
 
  • #9
Drakkith
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i just couldnt understand the language of wiki so could u please help me out!

Electrons usually pair up in their atomic and molecular orbitals. To do this, they have to have opposite spins (Typically called spin "up" and spin "down"). This cancels out the magnetic field from each of the electrons. But in certain materials, such as iron, one of the electrons isn't paired up, so nothing cancels its magnetic field. When this happens, the iron can become aligned so that the magnetic field of many of these electrons all add up and can generate a macroscopic magnetic field. This is where ferromagnetism comes from.

how an electron cant have a spin because they have an angular momentum i.e spin angular momentum then why?

In classical terms only spinning objects have angular momentum. That means that something must be spinning around an axis. However, for subatomic particles, this view is incorrect. For example, for an electron to be physically spinning around its axis fast enough to generate its magnetic field it would need to be spinning faster than the speed of light. Which is not possible. Instead it has intrinsic angular momentum, much like it has intrinsic mass, charge, etc.
 
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  • #10
harjot singh
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but actually i am saying can it be possible that the electrons through their spinning could provide a torque to the nearby particle like the protons or positive ions?
 
  • #11
Drakkith
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but actually i am saying can it be possible that the electrons through their spinning could provide a torque to the nearby particle like the protons or positive ions?

I don't believe so.
 
  • #12
harjot singh
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but how can spinning give rise to magnetism?explain me what is actually spin and how it give rise to magnetism i m little confused
 
  • #13
Drakkith
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but how can spinning give rise to magnetism?explain me what is actually spin and how it give rise to magnetism i m little confused

I've already explained what spin is. But I'm afraid I can't explain the magnetism part. It looks to me like the magnetic field arises from having intrinsic angular momentum, but I'm not sure.
 
  • #14
harjot singh
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but spin how canspin be the cause of magnetism i am not able to find it yet anywhere
 
  • #15
harjot singh
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antell me whether here the magnetic field produced by electronis its electrostatic field only due to its charge or its a kind of another!!
 
  • #16
michael879
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electrons are fundamental particles until today, so you can't really see them as spinning balls in order to give them that spin. In fact it's impossible to give it to them that way, since it would need them to spin faster than the speed of light (you know their spins, you know their radius boundary, so you can calculate the corresponding speed v, to find v>c).
under EM field, the spin itself spins around the Magnetic field...(spin transition)

This is actually a hugely quoted fallacy. If you use the relativistic expression for angular momentum there is a v < c for any R that gives the correct angular momentum. However v=c is really the only speed that makes sense, since you can't "slow down" an electrons spin, and I believe the radius you get by requiring J=hbar/2 is well over the experimental upper bound
 
  • #17
michael879
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Sorry, to answer the OP: nobody really knows what spin is, but it acts like classical angular momentum in a lot of ways. That is, spin+angular momentum is conserved.

Currents produce magnetic fields, so classically speaking any charged object with angular momentum will have a magnetic field associated with it. Quantum spin also produced a magnetic field, although it is twice as strong as you would expect classically. Again, there is no generally accepted explanation of what is actually happening, but quantum field theory models it with incredible accuracy
 
  • #18
harjot singh
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is it true in saying that a proton attracts the other electron due to its magnetic field because so far we had known through relativity that magnetic field is nothing but the electrostatic field?
 
  • #19
Drakkith
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is it true in saying that a proton attracts the other electron due to its magnetic field because so far we had known through relativity that magnetic field is nothing but the electrostatic field?

No, the proton attracts the electron through its electric field. The magnetic and electric fields are combined into the Electromagnetic field, but it's still important to distinguish between which effect, electric or magnetic, is taking place.
 
  • #20
harjot singh
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but on what account we can distinguish them both because both are due to the existence of their charges? according to me here electric and magnetic is although both same but given different names to avoid misconception in which we are presently suffering?
 
  • #21
harjot singh
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but according to me spin just tells us whether the magnetic field produced will align with the magnetic field of others or just it gives its direction and the attraction or repulsion is based on charge,this is evident from seeing neutrons actually neutrons even have spin but no charge and also doesnt produce magnetic field? now tell me whether i am true or just give me some gud cause behind this spin?
 
  • #22
Drakkith
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but on what account we can distinguish them both because both are due to the existence of their charges? according to me here electric and magnetic is although both same but given different names to avoid misconception in which we are presently suffering?

Electric and magnetic effects are different from each other and are given different names because of this. The difference between them is basic physics and you can find plenty of information on wikipedia and a million other places.

but according to me spin just tells us whether the magnetic field produced will align with the magnetic field of others or just it gives its direction and the attraction or repulsion is based on charge,this is evident from seeing neutrons actually neutrons even have spin but no charge and also doesnt produce magnetic field? now tell me whether i am true or just give me some gud cause behind this spin?

Again, spin is a term for the intrinsic angular momentum possessed by a particle and it does much more than give rise to a magnetic field. For one thing, it plays an integral part in determining whether particles are bosons or fermions.
 
  • #23
harjot singh
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but in terms of magnetism you agree withmy point i have addressed here about spin or is there some more thing i need to get about spin in terms of magnetism?
 
  • #24
Drakkith
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but in terms of magnetism you agree withmy point i have addressed here about spin or is there some more thing i need to get about spin in terms of magnetism?

I'm sorry, I can't understand your previous post well enough to know what point you were trying to make.
 
  • #25
harjot singh
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(1) i was saying that spin is just the direction pointer of the produced magnetic field.
(2) it tells just whether the magnetic field produced will align with the magnetic field of others.
(3) this twofacts were evident from neutrons as neutrons have spin but no magnetic field.
 
  • #26
Drakkith
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(1) i was saying that spin is just the direction pointer of the produced magnetic field.
(2) it tells just whether the magnetic field produced will align with the magnetic field of others.
(3) this twofacts were evident from neutrons as neutrons have spin but no magnetic field.

That's not correct. The DIRECTION of the spin is what tells how it aligns with an external magnetic field. Neutrons also have a magnetic moment. (A magnetic field) Spin is much more than you are making it out to be.
 
  • #27
harjot singh
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in that case if neutrons have magnetic field then it means that electrostatic field is not rather the same as of magnetic field?
 
  • #28
harjot singh
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hey drakkith here u are even wrong because magnetic field of neutrons is antiparallel to the external magnetic field which means it cant align with the external magnetic field outside?
 
  • #29
Drakkith
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in that case if neutrons have magnetic field then it means that electrostatic field is not rather the same as of magnetic field?

Of course it's not the same thing.

hey drakkith here u are even wrong because magnetic field of neutrons is antiparallel to the external magnetic field which means it cant align with the external magnetic field outside?

Where did you get this? The neutron can align itself either parallel or antiparallel to the external field just like all particles can.
 
  • #30
harjot singh
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but why we generally say that magnetic field is same as that of electric field but only we have to change is our frame of reference and then why we are now saying that magnetic field is not same? i m just confused now.tell me whether the magnetic effect is due to the charge present on electrons?
 
  • #31
Vanadium 50
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Harjot, your English makes it hard to understand what you are asking. Worse, it appears you are not understanding the replies. Worse still, the tone is coming across as entitled and demanding. I think you may need to find a different translator (if you are using one) or to spend a bit more time on each message if you are not. But we're not communicating well now.
 
  • #32
harjot singh
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Harjot, your English makes it hard to understand what you are asking. Worse, it appears you are not understanding the replies. Worse still, the tone is coming across as entitled and demanding. I think you may need to find a different translator (if you are using one) or to spend a bit more time on each message if you are not. But we're not communicating well now.

sorry brother i will take care of it from future.
 
  • #33
harjot singh
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can anyone tell me whether the 2 spin up electron will attract each other or repel?
 
  • #34
vanhees71
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Spin is not a simple concept if you don't have the proper mathematical tools at hand. In this case, it's representation theory of the rotation group, SO(3), or in quantum theory its covering group, the SU(2). Quickly stated: The spin describes the behavior of an asymptotic-free single-particle state for such a particle at rest (vanishing momentum).

The best I can provide is to stick to phenomenology. The spin of charged elementary particles brings with it an intrinsic magnetic dipole moment. This is in a true sense an elementary magnetic field this particle (at rest!) intrinsically posesses as much like the electrostatic field it posseses due to its electric charge.

Further, also the electromagnetic (quantum) field is a dynamical entity in its own right. You cannot say the electric or the magnetic field are derived from each other but, according to the theory of relativity, these are six components of the electromagnetic field. Which of these components you call "electric" or "magnetic" field depends on the reference frame you choose, as much as which component of a vector you call the "x direction", depending on the (Cartesian) basis you choose to describe it.

The issue of spin becomes even more complicated when it comes to non-elementary particles, like the hadrons. A good example is, as already mentioned, the neutron, which has a vanishing net charge but consists of a very complicated state of quarks and gluons, which are bound by the strong force. The exact nature of this binding is not yet fully understood. In the naive parton picture you may say it consists of three quarks (one up and two down quarks), but these "valence quarks" are not the point particles you describe as Dirac fields in the QCD lagrangian. These socalled "current quarks" carry a mass of a few MeV, as inferred from lattice QCD and chiral perturbation theory compared to the explicit breaking of chiral symmetry (e.g., the finite value of the pion mass). This is a complicated issue in itself. A good review can be found in the particle data group's review of particle physics,

http://pdg.lbl.gov/2013/reviews/rpp2012-rev-quark-masses.pdf

Thus already the mass of the nucleon (proton or the neutron) is pretty complicated to understand. Only about 2% is due to the current-quark masses (i.e., the Higgs mechanism) the rest is due to the strong interaction in terms of a cloud of virtual gluons and "sea quarks" all together making up the nucleon.

The more complicated is the spin. It's not even easy to say, how to define the spin of the constituents and how the measured spin 1/2 of the nucleons is shared by them. This is ongoing research. The same holds for the associated magnetic moment of the nucleons, which after all are not elementary but complicated composite objects of finite extent as described above.
 
  • #35
harjot singh
37
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but the thing is whether the magnetic field produced by suppose a particle will show repulsion or attraction on the basis of its charge or due to its spin?
 

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