This paper is dedicated to the physical understanding of electrostatic forces with a one-dimensional reference problem. First a non-dimensional analysis prescribes the kind of assumptions to consider for the electric field model. An analytical study of electro-mechanical coupling is then performed to understand the type of non-linearity added by electrostatic forces, and static and dynamic analysis are used to define new characteristic parameters. To come closer to more realistic problems, cubic mechanical stiffness is added to account for the large displacement hypothesis prescribed for certain types of MEMS and damping effects are studied.