## Kirchhoff's rules

So far we have considered series connections and parallel connections separately. But when the circuits become more complicated, e.g. consist of a combination of series and parallel connections, we need rules that we can apply to this.

Let us now get to know the Kirchhoff's rules from Gustav Robert Kirchhoff, which apply to all DC circuits.

- Kirchhoff's rules
- 1. Kirchhoff's rule (knot rule):
- The sum of the currents flowing to a branching point (node) is equal to the sum of the currents flowing away from this branching point.
- The following applies: ${\mathrm{I.}}_{\text{1}}={\mathrm{I.}}_{2}+{\mathrm{I.}}_{3}+{\mathrm{I.}}_{4}+{\mathrm{I.}}_{5}+\mathrm{...}$
- 2. Kirchhoff's rule (mesh rule):
- When running through a closed circuit (mesh) in a specified direction of rotation, the sum of all voltages is zero.
- The following applies: ${U}_{\text{away}}+{U}_{\text{CD}}+{U}_{\text{R.}}=0$