Different methods for calculating force

["dfj_stevenson" <Douglas@xxxxxxxxxxxxx>]

Dear all,

Can someone please comment on the usage of
1) Field Energy
2) Coenergy
3) Maxwells Stress Tensor

When calculating force in Magnetostatic problems in FEMM. In 
particular what are the differences the three methods and when is it 
most appropriate to utilise a particular method. I am particularly 
interested in the basic mathematics and the numerical methods eg mesh 
density, precision that are involved.

Thank-you