# Green function

1. Jul 7, 2011

### rbwang1225

In Jackson's ED book, he mentioned eq. 2.18 is essentially the same as eq. 2.5. What I don't understand is that in eq. 2.18 it is the position of the unit source to be differentiated while in eq. 2.5 it is the observation point. Is this O.K.?

2. Jul 7, 2011

### Staff: Mentor

It might help if you provided the examples you were talking about. I know I don't have this book that you are referring to.

3. Jul 8, 2011

### clem

The two equations are for different things. That is why there are the two equations.
(2.5) is to get the surface charge for a given potential.
(2.18) is what is needed for the Dirichlet boundary condition using a GF.
That is one of the (many) difficult sections of J.

Last edited: Jul 8, 2011