The electric charge is a type of physical property of matter, scalar and signed, responsible for one of the fundamental interactions of matter, the electromagnetic interaction, and the source of the electromagnetic field. There are two types of electric charges: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral.
Precise measurements of electrical charges were carried out by the French physicist Charles Coulomb in the 1780s using a device called a torsional balance measuring the force generated between two electrically charged objects. The results of Coulomb’s work led to the development of a unit of electrical charge named in his honor, the coulomb. If two “point” objects (hypothetical objects having no appreciable surface area) were equally charged to a measure of 1 coulomb, and placed 1 meter apart, they would generate a force of about 9 billion newtons, either attracting or repelling depending on the types of charges involved.
Charge conservation is the principle that the total electric charge in an isolated system never changes. The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved. Charge conservation, considered as a physical conservation law, implies that the change in the amount of electric charge in any volume of space is exactly equal to the amount of charge flowing into the volume minus the amount of charge flowing out of the volume.