From PDE to linear algebraic equations. Algorithm of solver

Dear Sirs, please advise me with my deal.

I simulated a model in ACDC->Electric currents. As I can see there are some differential equations which FEM approximates into a system of nonlinear or linear algebraic equations. Tell me please

1. Where can I find these nonlinear or linear algebraic equations and input matrixes? I need them very much and nobody can tell me the specific details.

2. Where can I see the detail algorithm or program realization of Algebraic Multigrid solver?

What I want- I want to realize the Algebraic Multigrid Solver in Matlab and try to solve nonlinear or linear algebraic equations (not PDE) from my model in Matlab.

Thank you very much for any help!