When should I use one and when should I use the other? For example, suppose I have a rod of length 2L, with an edge on the point -L on the X axis and another on L. The rod is uniformly charged, with total charge Q>0. having that said, if i wanted to calculate the electric field in an arbitrary (0,y,0) point, couldnt I use Gauss's law, using a cilinder as my gauss surface? And if the field is not specifically radial, in order to calculate it for a (x,0,0) point, i would have to integrate using coulomb's law, considering it a continuous distribution, correct? So, the problem lies within the first problem: It gives me two different results wether i use the method described(Gauss's law), or if I use coulomb's law for continuous distributions of charge, and integrate from -L to L. which of the methods is wrong, and why?