Problem 16-5    Source:    Problem 4.62 - page 97 - NILSSON, James W. & RIEDEL, Susan A. - Book: Circuitos Elétricos - 5ª edição - Ed. LTC (Livros Técnicos e Científicos) - 1996.

The Wheatstone bridge in the circuit show in Figure 16-05.1. is balanced when R₂ = 3000 Ω. If the galvanometer has a resistance of R_i = 50 ohms, what is the current indicated by the galvanometer when R₂ = 3003 Ω? .

Solution of the Problem 16-5

To establish the necessary equations for determining the value of I_G , let's use the Kirchhoff method for currents and use the circuit shown in the Figure 16-05.2 for reference.

Thus, for the mesh indicated by the red arrow we have the equation:

And for the mesh indicated by the black arrow we have the equation:

And finally for the brown arrow, we have:

Therefore, we have three equations to three unknowns that solved by the program "Octave", we find the following values:

Therefore, we can state that the galvanometer will read an approximate value of 3.5 µA.