Used on its own, Ohm’s law is insufficient to determine the magnitude of the voltages and currents present in complex circuits. For these circuits we need to make use of two further laws; Kirchhoff’s current law and Kirchhoff’s voltage law.
22.1.1 Kirchhoff's current law
Kirchhoff’s current law states that the algebraic sum of the currents present at a junction (or node) in a circuit is zero as shown in Figure 22.1.
Kirchhoff's voltage law