Which principle states that the total electric charge in an isolated system remains constant over time?

The principle that states that the total electric charge in an isolated system remains constant over time is the principle of conservation of charge. This principle asserts that even though electric charges can be transformed from one form to another or can move from one part of the system to another, the overall quantity of charge remains unchanged. This means that in any process taking place in an isolated system, the sum of positive and negative charges will balance out to a constant value, ensuring that charge is neither created nor destroyed.

This principle is foundational in understanding electric interactions and is crucial in fields such as electrostatics and circuit theory. In essence, it's a way to describe the behavior of electric charge in a coherent and predictable manner.