[exDemMom]

(BTW this is a simple form of the equation and is only applied to point sources. Usually it is expressed as a vector equation)

That reminds me of when I took physics, and we kept talking about an electric field around an infinite wire. I know it was presented that way in order to simplify the mathmatics, but I got so hung up on the impossibility of an infinite wire that I couldn't grasp the mathmatics. For me, it would have been better to present the equations with all the modifications necessary to describe the distortions of electric field at the wire ends, because I can believe a finite wire.

[RadioAstronomer]

I understand fully! :-)

[RadioAstronomer]

Here ya go - "infinite wire" :-)

http://www.pa.msu.edu/~duxbury/courses/phy294H/lectures/lecture22/lecture22.html

[NonLinear]

That reminds me of when I took physics, and we kept talking about an electric field around an infinite wire. I know it was presented that way in order to simplify the mathmatics, but I got so hung up on the impossibility of an infinite wire that I couldn't grasp the mathmatics.

I had the good fortune to have an excellent physics professor. He talked about "an ecectric field around a wire, while for the moment, neglecting end effects."