Problem + Hard 55-1    Source:   Problem 12 - List of RLC Problems - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2011 - Prof. doctor Valner Brusamarello.

For the circuit in the figure below we have V = 5,   I = 3 + j4 and E = 40√2∠45°. Determine   Z,   X   and   V_ab.

Problem + Hard 55-2    Source:   Question 1 - List 1st area - Discipline Electrical Circuits of the School of Engineering - UFRGS - 1972 - Prof. doctor Sérgio Machado Bordini.

Problem + Hard 55-3    Source:   Problem 18 - List of RLC Problems - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2011 - Prof. doctor Valner Brusamarello.

For the circuit in the figure below, E is in phase with E₁ and the voltmeter V measures 60 volts. Furthermore, X is a component R , L or pure C.   Determine E₁,  E   and   X.

Problem + Hard 55-4    Source:   Problem 38 - List of RLC Problems - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2011 - Prof. doctor Valner Brusamarello.

For the circuit in the figure below we have to |V_R| = 2. |I|. We know that V_R is delayed 90° with respect to I. Furthermore, X is a component R , L or pure C.   Determine R and  X.

Problem + Hard 55-5    Source:   Adapted from Problem 30 - List of RLC Problems - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2017 - Prof. doctor Valner Brusamarello.

Knowing that V_ab = 60√3∠θ and that the voltmeter V measures 60 volts between the points 1 and 2, determine:

a) V_cb knowing that it is 30° behind V _ab.

b) The value of V_ac and I_T.

b) The values ​​of R and X.

Problem + Hard 55-6    Source:   Problem 33 - List of RLC Problems - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2017 - Prof. doctor Valner Brusamarello.

Determine the values ​​of R and X in the circuit of the figure below knowing that I = 1.6∠73.1°.

Attention - In the list of exercises at UFRGS, the answer to this problem has a typo. The correct answer is:   X = -9,  and  R = 1.5. The list contains X = 9. In this case X would be an inductor. It's not the case. X is a capacitor with reactance of 9 ohms, as will be demonstrated in the solution to the problem.

Problem + Hard 55-7    Source:   Problem 7 - RLC 2008 Problem List IV - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2008 - Prof. doctor Valner Brusamarello.

In the circuit below, determine the magnitude and phase of the voltage source E, and the value of Z (it is known that Z = X∠60°, where X is a constant to be determined). Also determine the value of the constant A, knowing that the current I₃ is 15 A and the voltmeter V reads 75 V. It is also known that the angle α is 60° ahead of V_ab. Note that the voltage over Z is provided in the circuit.

Resistors Values:   R₁ = 10√3Ω   R₂ = R₃ = 2.5√3 Ω

Problem + Hard 55-8    Source:   Adapted from Problem 4 - RLC 2008 Problem List IV - Discipline Electrical Circuits of the School of Engineering - UFRGS - 2008 - Prof. doctor Valner Brusamarello.

In the circuit below, the voltmeter V measure 70 volts. In addition, the voltage E is 30° behind V_ab. Determine the magnitude and phase of the voltage source E, as well as the value and nature of X. Also determine the value of V_ab , I and the voltage V_ca. Make one phasor diagram of the main voltages in the circuit.