What is Conservation Of Charge?

When a glass rod is rubbed with silk, a positive charge appears on the rod. Measurement shows that a corresponding negative charge appears on the silk. This suggests that rubbing does not create charge but merely transfers it from one object to another, disturbing slightly the electrical neutrality of each. This hypothesis of the conservation of charge has stood up under careful experimental tests both for large-scale objects and for atoms, nuclei, and elementary particles. No exceptions have ever been found.

In analogy with other conservation law, such as conservation of momentum or conservation of energy, we can express conservation of electric charge as

Σq = constant or q_i = q_f.

In any process occurring in an isolated system the net initial charge must equal the net final charge. In finding the net charge, it is important to take into account the signs of the individual charges.