Coupled Physics

Hi i'm a beginner and i don't know a lot about multiphysics simulation. I solve a model with

drift-diffusion equations (variable of the phyisic: quasi fermi potential FIn) coupled with

piezoelectric equations (variables of the physic: electric potential V, displacement u) coupled with

thermal stress (variables of the physics: Temperature T, displacement u).

The model works very good but i don't know if Comsol take the displacement u as a variable for both physics (Piezoelectric and thermal stress). My question is:

"putting the same variable name in two or more physics allow comsol to solve for this variable all the physics equations associated?" or solve only for one physics? i cannot find this on the manual!

Thanks