Surface Density of Loads
A body in electrostatic equilibrium, that is, when all possible responsible for its electrification lie on its surface, can be characterized by its average surface density of charges. which by definition is the result of the electric charge quotient Q, by the area of its surface THE.
Being its unit adopted in SI the C / m².
Note that for negative charges the average surface density of charges is also negative since the area is always positive.
The average term is used since electric charges are hardly evenly distributed over the entire surface of a body, so it is possible to see that the modulus of this density is inversely proportional to its radius of curvature, that is, in sharp electrified objects. there is a higher concentration of charge at its end (tip).
Uniform Electric Field (CEU)
We say that an electric field is uniform in a region when its lines of force are parallel and equally spaced from each other, implying that its electric field vector in this region have at all points the same intensity, direction and meaning.
A common way to achieve a uniform electric field is to use two flat and equal conductive plates. If the plates are laid parallel, having charges of the same intensity but of opposite signal, the electric field generated between them will be uniform.