Electron spin? how?

  • #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
in that case if neutrons have magnetic field then it means that electrostatic field is not rather the same as of magnetic field?
 
  • #28
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
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, 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
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
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?
 
  • #36
ChrisVer
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it will be a small repulsive or attractive force which would lead to somehow higher and lower energy state (so the ground state would require antiparallel spins). What is the problem about that? It comes from the coupling of magnetic field with the spin.
It doesn't make the spin as the classical angular momentum in anyway. The angular momentum is given by a cross product of position and momentum. This is not true for the spin
 
  • #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?

I think you need to read up on basic electromagnetism, as you don't seem to understand the classical concepts and without them the quantum mechanics would be even more confusing. I've found 2 repeated issues that make your questions nonsensical:

1) The magnetic force is velocity-dependent so you can't talk about attraction or repulsion without specifying velocities. However, to try to answer your question: the magnetic effects are due to BOTH charge and spin angular momentum. Neutrinos have no magnetic field, but they have spin (neutrons are made of charged quarks so they have magnetic moments). Similarly a charged scalar particle would have charge but no spin, and have no intrinsic magnetic field

2) The terms "spin up" and "spin down" only make sense relative to some fixed coordinate basis, like in reference to an external magnetic field. Using the words "up" and "down" implicitly turns a vector quantity (spin direction) into a scalar by taking its dot product relative to some OTHER vector. The concept of spin makes a lot more sense when you deal with the vector quantity rather than some arbitrary scalar
 
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  • #38
Actually i appreciate your answer to my question but still i want to know how spin and charge can create magnetic dipole which according to me is superficial because i am still on my point that magnetic field is on the basis of spin.Although with your example of neutrino you have proved it but still explain me how magnetic field can be "created" by charge and spin?just explain me everything and not just a normal as we generally do.

Regards
Harjot
 
  • #39
Vanadium 50
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Harjot Singh, you have received some excellent advice on what you need to study to understand the question you have asked. "Explain me everything" is not how we operate here, for the simple reason that it doesn't work. If you want to learn, you need to put a certain amount of effort in.
 

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