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B Energy, charge and electric field

  1. Jun 26, 2017 #1
    Hi there,

    Im familiar with the concept that electric field has associated energy with it
    Now if in space an electron apppeared at some instant t=0 then electric field will not be established instantaneously but will propagate at speed of light through space
    As electric field is bieng established energy associated with it is changing with time
    Now what is causing that change in energy although there is no change in charge placed there and no other interaction are seeming to be there to cause change in energy .pls help me understand this .
    Any help will be appreciated
     
  2. jcsd
  3. Jun 26, 2017 #2
    The problem is that you created an unphysical scenario (if I understand it correctly, your wording is very confusing). Charges don't just appear magically in place, they need to be transported in from somewhere else. That is, your scenario directly violates the conservation of energy, but your question is exactly about that aspect, the total energy.
     
  4. Jun 26, 2017 #3
    In high school we are taught about decay of neutron into proton and electron with antineutrino .
    I have just passed high school so i am not having enough knowledge but still i think that in this process proton and electon are generated instantaneously in the space which initially was having no charge particles and also i think these are not generated at same place .
    So i think my question makes some sense
     
  5. Jun 26, 2017 #4
    While particles can indeed be created out of energy, the total sum of charge however is conserved, just like energy:

    https://en.m.wikipedia.org/wiki/Charge_conservation

    So, you can't just create an electron from energy, there *has* to be a positive charged particle created at the same time to keep the total sum the same.
     
  6. Jun 26, 2017 #5
    , there *has* to be a positive charged particle created at the same time to keep the total sum the same.[/QUOTE]

    Is that positively charged particle has to be formed at the same position as that of electron?
     
  7. Jun 26, 2017 #6
  8. Jun 26, 2017 #7
    I didn't get that ??
    How can electon and proton be at same position at same time
     
  9. Jun 26, 2017 #8
    They are only in the same spot for an infinitesimal small amount of time, since they are flying away from each other. Look into how particle accelerators work, that's really the same principle.

    Also, IIRC you can't create an electron and a proton on their own. I believe the latter would have to be a positron (i.e. an anti-electron)
     
  10. Jun 26, 2017 #9
    Why are they flying apart as attractive force between them will be infinite when they are at same position
     
  11. Jun 26, 2017 #10
    When it comes to these things, you can't look at it from a classical, static point of view. This is quantum mechanics, where particles aren't exactly in one spot but rather exist in a cloud of probability, and they also often have a large kinetic energy.

    https://en.wikipedia.org/wiki/Pair_production
     
  12. Jun 30, 2017 #11
    It's the same principle with how particle accelerators work :wink:
     
    Last edited: Jun 30, 2017
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