Force Due to Electric Field

I am trying to obtain the force due to electric field.
If someone can help me' that'll be great

Here is my case
- electrostatic module
- Upper Surface of the airfoil has two copper electrodes (one on the surface the other embedded inside the airfoil)
-Airfoil is a dielectric silicon
- The rest of the domain is air
- 8000V to the electrode on the surface, and -8000V to the embedded electrode


I want to know the force due to the electric field from these electrodes.
I've used force calculation node, and defined its domain as air, but it shows the force is constant throughout the domain

Any help will be appreciated.