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Motion of electron

  1. May 4, 2015 #1
    what is the background force for the motion of electron?
    is any other sub atomic particle can move? if no why?
     
  2. jcsd
  3. May 4, 2015 #2
    The Bohr model of the atom, consisting of a nucleus with electrons orbiting around it like a mini solar system, is no longer considered an accurate picture. Instead, quantum mechanics says that an electron in an atom doesn't have a definite position, but instead takes the form of a 'cloud of probability' covering the locations where the electron is likely to be found. This cloud is called an orbital, but the electron doesn't travel round the nucleus in the classical sense. That being said, the Bohr model is still taught below the undergraduate level because it shows the general structure of the atom.

    Outside the atom, the motion of free electrons is most often caused by the electromagnetic force - electrons have charge -1, so are attracted to positive charges and repelled by negative ones. Kinetic energy can also be given to electrons via the weak nuclear force, which occurs in beta decay, and through direct absorption of energy from photons as seen in the photoelectric effect.

    Most subatomic particles can move freely - the proton has charge +1, so feels the electromagnetic force in the opposite way to electrons. Neutrons do not have charge, but can be given kinetic energy in fission processes or by collisions with alpha particles, for example. Quarks, on the other hand, have charge, so can be moved by the electromagnetic force, but they also feel the strong nuclear force, whose magnitude increases with quark separation. After very short distances it becomes so strong that quarks can never be truly free - they are always confined inside larger particles called hadrons, the proton and neutron being two examples.
     
  4. May 4, 2015 #3

    DrClaude

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    Staff: Mentor

    Electric fields can accelerate electrons. All sub-atomic particles can move.

    Your question is not very clear. Why are you under the impression that only electrons can move?
     
  5. May 5, 2015 #4
    electron have two type of motion spinning and rotation .
    is any other sub atomic particle can move without the appliction of an external field?
     
  6. May 5, 2015 #5

    DrClaude

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    Staff: Mentor

    By "spinning" I guess you mean the electron spin, which is an intrinsic angular momentum and can't be considered as "motion." Otherwise, electrons can move any which way. A good example can be found in a cathode ray tube.

    All particles can move, and external fields are not necessary, collisions for instance can do the trick. At any instant, billions of neutrinos from the Sun are passing through your body. In particles accelerators and in the high atmosphere, fundamental particles are being created all the time and travel a while before decaying or hitting something.
     
  7. May 5, 2015 #6
    thank you sir
     
  8. May 6, 2015 #7
    I realise this may be a bit off topic but I came across an interesting paper the other day from 1985 by Ohanian: http://people.westminstercollege.edu/faculty/ccline/courses/phys425/AJP_54(6)_p500.pdf
    If you consider the expectation of momentum density (from the symmetrised energy density tensor form) in the Dirac field about some axis, you get 2 contributions: orbital angular momentum and spin - analogous to the case of a circular polarised wave in the EM field. He basically shows that one can interpret spin as arising from a circulating flow of energy in the Dirac field. So spin 1/2 doesn't have to be viewed as some intrinsic property of electrons, it can be understood as a property of circulating energy flow in the electron field.
     
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