Block diagrams are well suited for the modelling of control systems .
See for example the simple electric circuit in the figure below. Given the physical device, it is straightforward to draw the electric circuit diagram shown on the left side of the figure. Transforming the electric circuit into the block diagram in the middle of the figure needs some work and is not practical for larger circuits. Furthermore, the physical insight provided by the electric circuit diagram is lost in the block diagram. Block diagrams are inappropriate for the modelling of physical systems because they are designed to visualize signal flow .