Kirchhoff's current law
When analyzing electric circuits, two basic laws of electricity are the most useful, Kirchhoff's current law and Kirchhoff's voltage law. These equations often use either the branch method, the loop current method or the nodal method to create a set of linear equations that must be solved to determine all of the voltages and currents in a complex electrical circuit.
Kirchhoff's current law can be stated as: "At any junction of wires in a circuit, the sum of all currents entering the junction exactly equals the sum of all the currents leaving the junction. In other words, electric charge is conserved."