# Electric potential due to a current source - Basic equations

In my book I found the folowing formula of the electric potential generated by a current source:

$$\Phi = \frac{I}{4 \pi \sigma} \frac{1}{r}$$

where I is the current, $$\sigma$$ the electrical conductivity, r the distance between the current source and a generic point P.

I'd like to know which are the basic equations from which the above formula comes from.

EDIT

Thank you in advance.

• Which book and what is covered in the earlier pages / chapters... – Solar Mike Jun 9 at 15:14
• Hello @SolarMike the name of the book is "Biomechanics and motor control of human movement" by Winter. In the previous chapters there are topics about biomechanics, not about electricity. The sentence in the post is in the first paragraph of the only chapter who talk about "electricity", actually electromyographic signals. – Gennaro Arguzzi Jun 9 at 15:40
• This is the potential due to a current source connected to some particular physical system. I don't know what kind of system this equation applies to , but it might be something like an electrode on a surface, or embedded in a sheet of material, or in the center of a sphere of material, etc. You should read carefully to see what system they're discussing. – The Photon Jun 9 at 16:22
• Hello @ThePhoton, now i'm posting the figure of the system. The author draws directly two current sources. Anyway the same approach is used also in geophysics. – Gennaro Arguzzi Jun 9 at 16:25