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Homework Help: Derivation of Larmor formula

  1. Nov 7, 2014 #1
    1. The problem statement, all variables and given/known data
    I need to derive this formula, and I'm basing it upon the following method (this has the diagram which I will be talking about below)

    3. The attempt at a solution
    I'm fine with everything apart from the reasoning that the parallel field lines (from where q is, and where it would be) have to join up in the middle region. The reasoning for this is given as

    'A field line such as AB lies on a cone around the x axis which includes a certain amount of flux from the charge q. If CD makes the same angle θ with the axis, the cone on which it lies includes the same amount of flux. Hence AB and CD must be parts of the same field line, connected by a segment BC.'

    I don't see how the cones having equal flux implies the two field lines must be the same and so joined. Could anybody explain this? Thanks!
  2. jcsd
  3. Nov 8, 2014 #2
    Anyone please? It won't take too long to read the derivation!
  4. Nov 8, 2014 #3


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    I've tried a couple of times to view the PDF, but it comes up blank on my system. Maybe others have the same problem.
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