Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Current loops and electric dipoles

  1. Feb 8, 2014 #1
    Hello Physics enthusiasts

    Imagine an infinitesimal small current loop where the current can run clockwise or counterclockwise at frequency v. I am trying to find a linear combination of the two(current loops) which creates the same electric field pattern (far from the dipole) as a very small current running on a very small line(electric dipole).

    In principle it should be possible but I am not sure how to tackle the problem. Could you please help me with this?
     
  2. jcsd
  3. Feb 8, 2014 #2

    Dale

    Staff: Mentor

    I suspect that it is not possible in principle. A small current loop gives a magnetic dipole field, so two loops in general gives a magnetic quadrupole field. I don't know any reason to believe that a magnetic quadrupole should give an electric dipole.
     
  4. Feb 8, 2014 #3

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

  5. Feb 8, 2014 #4

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Equal clockwise and anti-clockwise currents in a loop of radius R, oscillating at an angular frequency
    w=c/R would be equivalent to an electric dipole.
     
  6. Feb 8, 2014 #5

    Dale

    Staff: Mentor

    Are you sure of that? It would surprise me.
     
  7. Feb 9, 2014 #6
    I also think that it shuld be just a linear combinition of the two right and left propagating currents that give the solution but I can't derive it mathematically. Any suggestion?
     
  8. Feb 9, 2014 #7
    Thanks for the reply. It is an electromagnetic source of energy, but this dose not mean that it behaves the same way as a dipole, neither it means that a combination of clock and counterclockwise current loops will give a linear dipole. I am kind of looking for a solid mathematical argument.
     
  9. Feb 9, 2014 #8

    Dale

    Staff: Mentor

    I would think that it would be at least quadrupole, but my "multipole kung-fu" is admittedly weak :smile:
     
  10. Feb 9, 2014 #9
    Are the currents nearly superimposed? If so the net current is zero, you got nothing? What am I missing?
     
  11. Feb 9, 2014 #10
    A general alternating current is the sum of a part that has a divergence and a part that has a curl? Don't those different alternating currents give rise to fundamentally different radiation fields?
     
  12. Feb 10, 2014 #11

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I'm sorry. My previous posts were wrong. Please forget them,
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Current loops and electric dipoles
  1. Electric dipole (Replies: 6)

  2. Current Loop ? (Replies: 16)

Loading...