Geometry of the DC motor:
The model of DC electric motor with permanent magnets you can analyze for:
The calculations are performed to investigate the mechanical torque (per 1 m depth) in the function of the yoke thickness and the current density (also other characteristics of materials). You can observe the saturation effect of the mechanical torque with the steel yoke growth and a deformation of the field lines with the current density growth. This information can be useful in a design process.