# Dirichlet boundary conditions

Hi, I am using the finite element method to solve current flow in earth. So far my problem is this Consider a square,

            (air)
----(1)------ (air-ground suraface)
|           |


|(ground) (2).................... (3) (ground).

        |           |
|           |
-----(4)-----
(ground)


In (1) (air-ground) I use the homogeneous Neumann conditions, (which the algorithm takes automatic account for).

I make (2)(3)(4) quote large so I apply homogeneous dirichlet conditions. Current is injecting from some points in (1).

I want to modify it so now (2) (3) and (4) be also air. Obviously now homogeneous dirichlet is not the case.

I am thinking two options. 1) If I don’t use dirichlet conditions, then neuman wouldn’t be calculated automatically? Do I need something more? 2) Shall I use any other boundary conditions is (2)(3)(4)?

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