Finding the fields from 2 electric dipoles

1. May 1, 2004

Norman

How would I go about finding the fields from 2 electric dipoles say a distance d apart... I know they will simply sum... but I am having trouble thinking of how the dipole moment of the dipole at position a would look. I am drawing a blank here and it is getting frustrating.
Thanks,
Norm

2. May 2, 2004

flexten

Well, i don't work too much with electric fields, but if it was an acoustic field:
Each diplole has a pattern associated with it, i seem to recall it is a cos.
For a far field pattern, draw a plane perpendicular to the direction of interest and compute the distance of each diplole from it, then sum with an sin(kd) for each and superpose the dipole pattern from each source.

If it's in the nearfield then maybe use a freespace Green's function like (e^Z)/Z where Z=-jkd, i think that's the right one for potential anyway. And of course superpose the individual source patterns.

The individual dipole pattern is just a pair of monopoles separated much much less than a wavelength with opposite sign, using a far field pattern.

Hope this helps some,
Best

3. May 3, 2004

turin

Norman,
Do you have a picture? I'm having trouble understanding your question. Are you asking how the field from just one dipole would look? (and then you know, once you have that, to use the superposition principle) Do you know about Legendre functions?

4. May 4, 2004

Norman

Sorry it was a poorly phrased question... I figured it out though. I had two oscillating dipoles seperated by a distance d. I wanted to, in the end, find out what their radiation fields looked like for all space. Since there was no net charge, my dipole moment was independent of coordinate system but there was a phase factor difference between the fields created by each.
Thanks for the interest.
Cheers,
Norm