Why is charge conserved

This image shows the nuclear process of a beta decay, where a neutron decays to a proton and an electron. The net charge before and after the event is the same by this law.

Wilson and A. Buffa, "Electric Charge" in College Physics , 5th ed. Conservation is a common theme in chemistry and physics. When you balance chemical equations , you are ensuring that the total number of atoms remain constant throughout the reaction. Here, it is the conservation of mass that is concerned. Another common conservation principle is energy. We usually use this principle in physics when we equate the initial energy of an event to the final energy of an event. To give a brief quantitative overview of electric charge, the unit for charge is the Coulomb, denoted by "C".

These are referred to as the elementary charge. However, the laws of physics, extrapolations of local measurements, and simple reasoning seem to all tell us that the overall electric charge of the universe is exactly zero. In other words, there is exactly as much positive electric charge in the universe as there is negative electric charge.

The theoretical reason for making this conclusion is the Law of Conservation of Charge. Because of certain symmetries in the structure of the universe, the total electric charge of an isolated system is always conserved. This means that the total charge of an isolated system is the same at all points in time. The Law of Conservation of Charge is a fundamental, strict, universal law. In thousands to millions of different experiments, this law has never been observed to be violated, not even once.

Furthermore, this law is the only logical way to explain the world around us. But somehow it is okay to destroy two oppositely charged particles at once! Why is that so? Let's just take a look at electron-positron annihilation; Two equally oppositely charged particle are bombarded into each other, both are instantly destroyed lose their existence and gamma ray photons emerge. But certainly it also raises the question what if you observe only a positron or an electron, in observed system certainly charge will not be conserved however overall it maybe.

It jumps out and say that you cannot destroy individual charges, but if you get 2 equally and oppositely charged particles we can destroy both! Since, clearly it can be destroyed, just in pairs also created in pairs. No, we have not been taught that. We've been taught that electric charge , i. Imagine that, within some volume there is some net electric charge Q.

Assuming there is no current through the boundary of the volume, we are taught that the net electric charge within the volume will always be Q. This comes from the continuity equation. Now, the fact that Q does not change with time does not imply that pairs of oppositely charged particles cannot be created or destroyed.

This means that the number of positively charged particles must equal the number of negatively charge particles at all times.