region and u03c1 charge density of the electric field region we note that permittivity r is close to zero within a conductor thus the permitivity function u25a1 x y z contains a description of the geometry of the system relative to the coordinates of the conductors further integration of poisson 39 s equation over x y z space can be performed assuming a boundary condition of constant potential for the applied voltage within the conductor the integration of poisson 39 s equation produces the capacitance matrix c of capacitances c ni between the conductors that describes the charges on the conductors as a result of the applied voltages similarly considering the heat equation which is shown in equation 2 as we note that the thermal conductivity u03ba between metal conductors is significantly smaller than within a conductor thus the thermal conductivity function u03ba x y z contains a description of the geometry of the system relative to the coordinates of the conductors therefore in the thermal case we can also 1 make the approximation that the temperature within the conductor is constant 2 set this constant as a boundary condition at a given value and 3 solve the heat equation the result is a matrix g of thermal conductances g thi between.