How are 2D electrostatic modules approximated in COMSOL?

[feynman1]

In 2D modules, the 3rd direction isn't shown in model settings. What assumptions are made regarding electrostatics 2D modules?
For example, how is a 2D Poisson's equation with point sources solved? Is it based on a 1/r potential or a log potential?

 

[DrClaude]

It is my understanding that the calculation represents a 2D slice of a uniform model in the z direction, as if it ws extending to infinity.

 

[feynman1]

It is my understanding that the calculation represents a 2D slice of a uniform model in the z direction, as if it ws extending to infinity.

Is there anywhere I can find the documentation about this?

 

[DrClaude]

Pages 64-65 of the AC/DC Module User's Guide (for version 5.4, available here):

The following is a guide through some of the common approximations made for 2D problems. Remember that modeling in 2D usually represents some 3D geometry under the assumption that nothing changes in the third dimension.

Cartesian Coordinates
In this case you view a cross section in the xy-plane of the actual 3D geometry. The geometry is mathematically extended to infinity in both directions along the z-axis, assuming no variation along that axis. All the total flows in and out of boundaries are per unit length along the z-axis.