- The fundamental elementary charge is carried by electrons (negative charge) and protons (positive charge).
- Both electrons and protions are mobile. For isntance, electrons in their trajectories around the atomic nucleus and protons in the translation of the atoms.
- If an object has a non zero net charge, it means that there is an excess of positive or negative charge, related to the opposite charge. For instance, if in a material there are more electrons than protons, then, the material will be charge negatively.