The conservation of energy and conservation of charge when applied to electrical circuits are known as Kirchoff's laws.
Conservation of energy - zero algebraic sum of the voltage drops around a closed circuit loop (imaginary loop)
Conservation of charge - zero algebraic sum of the currents flowing into a point (total charge in, equals total charge out)
When applying these laws to solve for circuit unknowns we will find the following definitions useful:
Using these definitions we can apply Kirchoff's laws to a circuit to solve for the unknown quantities. The general procedure is:
But before we look at general circuits lets consider how simple resistors add.