Does electrical field intensity force equation apply to non-circular objects?
If you measure the field intensity close to the object, you will notice different readings near the corners due to fringing.  But as you retreat far away from the object (about a factor of 10 times the dimension of the object), the fringing effect will become unnoticeable and it will look just like a sphere (the circular object you mentioned?).  Coulomb's law is absolute and cannot be modified: it's the definition of the strength of an electric field i.e. the field intensity!