Co-energy: definition

[wingsw]

Can someone give a general definition of co-energy? There was a post here but about the particular case of an electromagnetics system, same on wikipedia (but even there not the general case(!)) I'm looking for a general definition (well, the case of the hamiltonian of a mass-spring system exactly)
Thanks in advanced

 

[electricpete]

Here you can find out about coenergy

https://en.wikipedia.org/wiki/Coenergy

It can be used to predict force and torque in non-linear electromagnetic system.

I think the analogous approach in mechanics is LaGrange equation.

https://en.wikipedia.org/wiki/Lagrangian_mechanics

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(2B)+(2B)' ?