Help with Jackson Electrodynamics Notation

  • Thread starter montyhp
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  • #1
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Homework Statement



I am having some difficulty with Jackson's notation.

I am coming from an engineering (not physics) background.

First of all, on Page 36 at the bottom of the page, Jackson uses the Dirac delta function d(x-x'). When he integrates his answer is the function at x instead of at x' as I would expect from the discussion on Page 26. Maybe this doesn't matter, but remember, you are talking to an engineer, so I need to understand the physical relevance.

My real question is, when Jackson starts working with Green's theorem, he uses x' as the location of his point charge in "Green Space" and as his integration variable. He then makes is integrals over d3x' and da'. Then he takes n' to be his normal vector and changes it to z' (n'=-z'). I understand why n=-z, but I don't understand the physical significance of the prime in this case. I still think that the prime refers to the location of the point charge in "Green Space".

Homework Equations



See Above

The Attempt at a Solution



This is in reference to problem 2.7 which I am working, but I am not asking for a solution. Just need help with the concept.

Thanks in advance
 

Answers and Replies

  • #2
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OK so I wrestled with Jackson Problem 2.7c some more and I think I have come to the following realization (is this right?):

The unprimed coordinates (r,th,z) are the location where we are trying to find the potential (our viewpoint). The primed coordinates (r',th',z') are the location of the charge on the disk (which is why we integrate in the primed coordinates because we are integrating to find the charge distribution). So in Problem 2.7c where we have to find the potential along the z axis, we set unprimed r=0 and integrate WRT r' (and th') over the surface of the disk. At least that gives me the correct answer.

Is that correct?

Also, I still don't understand why Jackson P 36 (blue version) seems to interpret the delta function "backwards" in eq 1.36. Can anyone help me with that?
 

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