1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electromagnetic field emitted by a charge

  1. Oct 21, 2006 #1

    What is the precise form of the electromagnetic field generated by a single charge q at a given point P and time t1, if the movement of q is described by M(t). I have seek the precise answer to this question in many books of physic, without success. I think it must be relativistic. Please, does someone have information in this subject?

  2. jcsd
  3. Oct 21, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper

    The precise answer is relativistic. It is usually formulated in terms of the retarded electric and magnetic potentials associated with charge and current densities.

  4. Oct 21, 2006 #3


    User Avatar

    Staff: Mentor

    See Griffiths, "Introduction to Electrodynamics" (2nd edition), section 9.2.2 (pp. 421-426).

    Or Jackson, "Classical Electrodynamics" (2nd edition), section 14.1 (pp. 654-658).
  5. Oct 28, 2006 #4
    Jackson is extremely difficult to read, even by those who have an excellant grasp on math and EM. In my humble opinion its best to go with Griffith.

    Best wishes

  6. Oct 28, 2006 #5

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Griffiths gives the correct answer in Eq. (9.107), but leaves out about two pages of derivation in getting to it. That's why he is simpler.
    If you want a derivation (but, it's complicated), you can find one in Franklin, "Classical Electromagnetism", Sec. 15.4.2. The result is still difficult to use because it is in terms of the retarded time, which leads to all kinds of problems. For a particle moving with constant velocity, the fields can be given in terms of the instantaneous time by
    [tex]{\bf E}= \frac{q{\bf r}}
    {\gamma^2[{\bf r}^2-({\bf v\times r})^2]^{\frac{3}{2}}}[/tex],
    and B=vXE.
  7. Oct 28, 2006 #6


    User Avatar
    Staff Emeritus
    Science Advisor

    You might also try : http://www.phys.ufl.edu/~rfield/PHY2061/images/relativity_14.pdf [Broken]

    Replace the "14" in the above link with different numbers, you'll get more slides showing the derivation.

    You might also try http://en.wikipedia.org/wiki/Relativistic_electromagnetism, though it's lacking diagrams at the moment.
    Last edited by a moderator: Apr 22, 2017 at 1:40 PM
  8. Oct 30, 2006 #7

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The Field pdf gives only the constant velocity field, which is the easy part.
    The Wikipedia page is confusing, and gives the wrong answer for the E field of a moving charge. I would try to correct the Wikipedia page, but I don't want to abet a crime.
    Last edited by a moderator: Apr 22, 2017 at 1:42 PM
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Electromagnetic field emitted by a charge
  1. Electromagnetic field (Replies: 4)