Electric field generated by a small object I've just begun to study electrostatics and I've read the coulomb law, it describes the electric field generated by a point charge as characterized by a spherical shape. I think it is due to the fact that we idealize a point charge as a very small spherical mass.
In the book I'm reading (John David Jackson: Classical Electrodynamics) it's told that Coulomb used generic small objects for doing his experiments, so I suspect that every small object of any shape generates, for distances compared to its size, an electric field with a spherical shape.
Is this correct? Is it possible to understand why, or does it imply knowledge that I still cannot understand?
 A: One interesting fact is that for perfect spheres the radius doesn't matter for the produces field. A sphere with charge $Q$ produces a field proportional to $Q/r^2$, where $r$ is the distance to the center of the sphere, irregardless of the size of a sphere. For objects that differ from spheres you can use the multipole expansion. The multipole expansion is a formal way of writing down the field as increasingly more difficult approximations to the simplest case: a point particle. This is like the Taylor expansion of electrostatics.
The multipole might be a bit too formal for your current level of understanding so I will give a brief outline of the link I mentioned. To calculate the potential at some position $r$ due to a charged object you perform the following integral:
$$V(\vec r)=\frac{1}{4\pi\epsilon_0}\int_V\frac{\rho(\vec r')}{|\vec r-\vec r'|}dV'$$
with $\rho$ the charge density. If you haven't seen this integral yet hang on for a second. It can be shown (using a Taylor series actually) that this integral can be written as
$$V(\vec r)=\frac{1}{4\pi\epsilon_0 r}\int_V\rho(\vec r')\left(1-\frac{\hat r\cdot \vec r'}{r}+\mathcal{O}\left(\frac{r'}{r}\right)^2\right)dV'$$
When $r'/r$ gets smaller (when the distance gets much larger than the dimensions of the object) you can neglect more and more terms. If you only leave the '$1$' term (the monopole term) the integral becomes the total charge $Q$ and you get the formula for a point charge. The larger the distance and the better the object looks like a sphere, the less terms you need to describe the electric field.
A: 
so i suspect that every small object of any shape generates, for distances compared to its size, an electric field with a spherical shape

You are correct, it is an experimental fact,  which is modeled mathematically with a point charge, the field being $1/r^2$. it fits macroscopic charge distributions as long as the size of the charge distribution is within errors a "point". 
When one goes to the very small sizes that quantum mechanics is needed for explaining the behavior, new mathematical theories for interactions are used , which you will learn if you continue studying physics, quantum electrodynamics (QED). The quantum frame blends naturally with the  classical frame for large dimensions.
You have to understand that physics is the discipline that fits experimental obsevations/facts with mathematical models, taking extra axioms, called laws , postulates, principles to pick those mathematical functions that fit the data. 
A: 
so I suspect that every small object of any shape generates, for
  distances compared to its size, an electric field with a spherical
  shape.

Quantum mechanics aside, the actual geometry of the charge (sphere, oval, cube, etc) is not so important as its “compactness” relative to the distance from the charge where Coulomb’s law is applied. The closer you get the more compact that distribution has to be in order for Coulomb’s law to hold. So in order for the law to hold at any distance you simply assume the charge is concentrated at a “point”.
In view of the above, yes every small object of any shape generates, for distances large compared to its size, an electric field with a spherical shape. For that matter, a spherical shape, for distances much greater compared to its size, generates the same electric field as every small object. They all can be considered to be a point charge.
Hope this helps.
