Problema 5-2    Source:   Adapted of Problem 3.52 - page 61 - NILSSON & RIEDEL - Book: Circuitos Elétricos - 8ª edição - Ed. Pearson - 2010.

Use Delta-Star transformation and compute the resistance between points a - d in the circuit shown in Figure 05-02.1

Solution of the Problem 5.2

As the problem asks, let's use the transformations star-triangle to resolve it. Initially, we will calculate the equivalent circuit for the circuit highlighted in yellow, as shown above. Note that the highlighted circuit in yellow, represents a delta or triangle circuit. We need to transform it in a star circuit. Using the equations seen in Theory we calculate the equivalent circuit as can be seen in the Figure 05-02.2.

Now we can replace the star circuit in the original circuit. Look in the Figure 05-02.3 the new configuration. Note, in the right circuit, which resulted in two resistors of equal value (34 ohms) in parallel.

However, the parallel of the two resistors of 34 ohms results on 17 ohms, that together with the resistor of 3 ohms we obtain a resistor of: