1)What is the formal definition of a point charge? It is known, that coulomb's law , is valid for point charges? But the real world does not consist of point charges. And coulomb himself used two spheres in his experiments... 2)Another point, in many books I have found that they say, when spatial dimension of charge is much much less than the distance between the charges, they can be treated as point charges...Is this true? For eg. By this, can we say that an irregularly shaped boulder (with charge on it's surface) can be treated as point charge if the distance between it and a test charge is large (~ 500m.)? Won't we have to perform integration to find the exact field at the point of test charge?