Question

If the shape of an object is non uniform ,where is the surface charge density maximum

Answer 1

It's because of the electric field developed around the conductor.

If the shape of conductor is regular, the electric field lines are uniformly distributed and hence the charge distribution.

If the shape is not regular, the electric field lines are not uniform and hence, it orients the charge distribution to be non-uniform.

That's the reason why charge concentration of spherical electrodes is less than pointed electrodes.