law of interaction of fixed charges was opened in 1785 by the French physicist Charles Coulomb in his experiments, he studied the forces of attraction and repulsion of charged beads.Pendant conducted their experiments using a torsion balance, which he designed.These scales have a very high sensitivity.
In his experiments to investigate the interaction pendant beads, the size of which were much smaller than the distance between them.Charged body, the size of which can be ignored in certain conditions, referred to as point charges.
pendant conducted many experiments and found the relationship between the force of interaction between charges, the product of their modules and the square of the distance between the charges.These forces obey Newton's third law, for the same charges, they are forces of repulsion, and at different - attraction.Interaction of fixed electric charges is called Coulomb or electrostatic.
Electric charge - a physical quantity that characterizes the ability of bodies or particles to enter into the electromagnetic interaction.Experimental evidence suggests that there are two kinds of electric charges - positive and negative.Opposite charges attract, and the same name - a start.This is the main difference between the electromagnetic and gravitational forces that are always attractive.
Coulomb's law holds for all point charged bodies whose size is much smaller than the distance between them.The proportionality factor in this law depends on the choice of units.The International System of SI it is 1 / 4πε0, where ε0 - dielectric constant.
Experiments have shown that the strength of the Coulomb interaction obey the superposition principle: if the charged body interacts with several bodies at the same time, the resulting force will be equal to the vector sum of the forces that act on a given body of other charged bodies.
principle of superposition says that at a fixed charge distribution of the Coulomb interaction force between any two bodies will not depend on the presence of other charged bodies.This principle should be used with caution when it comes to the interaction of charged bodies of finite size, for example, the two conducting balls.If you bring a ball charged to a system consisting of two charged balls, the interaction between these two spheres will change due to the redistribution of charges.