Law of Conservation of Electric Charge
In physics, there are two very important principles concerning the electric charge.
First is the law of conservation of electric charge. This law states that:
The algebraic sum of all the electric charges in any closed system is constant.
The only way to change the net charge of a system is to bring in charge from elsewhere, or remove charge from the system.
Charge can be created and destroyed, but only in positive-negative pairs.
Conservation of charge is thought to be a universal conservation law. No experimental evidence for any violation of this principle has ever been observed. In particle physics, charge conservation means that in elementary particle reactions that create charged particles, equal numbers of positive and negative particles are always created, keeping the net amount of charge unchanged. Even in high-energy interactions in which particles are created and destroyed, such as the creation of positron-electron pairs, the total charge of any closed system is exactly constant.
The second important principle is:
The magnitude of charge of the electron or proton is a natural unit of charge.
We say that charge is quantized. That is, every observable amount of electric charge is always an integer multiple of this basic unit. This unit is called the elementary charge, e, approximately equal to 1.602×10−19 coulombs (except for particles called quarks, which have charges that are integer multiples of 1⁄3e).