Charge conservation law, one of the fundamental exact laws of nature, which states that the algebraic sum of the electric charges of any closed (electrically isolated) system remains unchanged, whatever processes take place inside that system. Established in the 18th century. The discovery of the electron, which carries a negative electric charge, and of the proton, which has a positive charge of the same magnitude, proved that electric charges do not exist on their own but are bound to particles (charge is an intrinsic property of particles). Other elementary particles carrying a positive or negative charge equal in magnitude to that of the electron were discovered later. Electric charge is therefore discrete: the charge of any body is an integer multiple of the elementary electric charge.
Since every particle is characterised by a definite electric charge of its own, in the field of physical phenomena where particles are not transformed into one another the charge conservation law can be regarded as a consequence of the conservation of the number of particles. Thus, when macroscopic bodies are electrified the number of charged particles does not change; only their distribution in space does, charged particles being carried from one body to another. In elementary particle physics, which is marked by processes in which particles are transformed into one another, the number of particles is not conserved — some particles disappear and others are born — but the charge conservation law is always strictly obeyed: the total charge remains unchanged in all interactions and transformations of particles. The birth of a “new” charged particle is possible only either with the simultaneous disappearance of an “old” particle of the same charge, or in a pair with another particle whose charge is of the opposite sign (for example, in the birth of a particle-antiparticle pair); and in all such transformations the other conservation laws must be obeyed as well — those of energy, momentum and so on.
The charge conservation law, together with the law of conservation of energy, “explains” the stability of the electron. The electron (and the positron) is the lightest of the charged particles, and so it cannot decay into anything: decay into heavier charged particles (a muon or a π-meson, for example) is forbidden by the law of conservation of energy, and decay into lighter neutral particles (a photon or a neutrino) is forbidden by the charge conservation law. The accuracy with which the charge conservation law holds can be judged from the fact that an electron does not lose its charge for at least 5*1021 years.
Since every particle is characterised by a definite electric charge of its own, in the field of physical phenomena where particles are not transformed into one another the charge conservation law can be regarded as a consequence of the conservation of the number of particles. Thus, when macroscopic bodies are electrified the number of charged particles does not change; only their distribution in space does, charged particles being carried from one body to another. In elementary particle physics, which is marked by processes in which particles are transformed into one another, the number of particles is not conserved — some particles disappear and others are born — but the charge conservation law is always strictly obeyed: the total charge remains unchanged in all interactions and transformations of particles. The birth of a “new” charged particle is possible only either with the simultaneous disappearance of an “old” particle of the same charge, or in a pair with another particle whose charge is of the opposite sign (for example, in the birth of a particle-antiparticle pair); and in all such transformations the other conservation laws must be obeyed as well — those of energy, momentum and so on.
The charge conservation law, together with the law of conservation of energy, “explains” the stability of the electron. The electron (and the positron) is the lightest of the charged particles, and so it cannot decay into anything: decay into heavier charged particles (a muon or a π-meson, for example) is forbidden by the law of conservation of energy, and decay into lighter neutral particles (a photon or a neutrino) is forbidden by the charge conservation law. The accuracy with which the charge conservation law holds can be judged from the fact that an electron does not lose its charge for at least 5*1021 years.