October 2023

Q. A 0-1 Ampere moving iron ammeter has an internal resistance of 50 mΩ and inductance of 0.1 mH. A shunt coil is connected to extend its range to 0-10 Ampere for all operating frequencies. The time constant in milliseconds and resistance in mΩ of the shunt coil respectively are (A) 2, 5.55                  (B) 2, […]

Q. A separately excited dc motor has an armature resistance 𝑅𝑎 = 0.05 Ω. The field excitation is kept constant. At an armature voltage of 100 V, the motor produces a torque of 500 Nm at zero speed. Neglecting all mechanical losses, the no-load speed of the motor (in radian/s) for an armature voltage of

Q. A 1000 × 1000 bus admittance matrix for an electric power system has 8000 non-zero elements. The minimum number of branches (transmission lines and transformers) in this system are (up to 2 decimal places). Ans: 3500 Sol:

Q. The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are 𝑗0.1 pu, 𝑗0.05 pu and 𝑗0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is 𝑗0.01 pu, then

Q. Consider a non-singular 2×2 square matrix A . If trace(A) = 4 and trace(A2 ) = 5 , the determinant of the matrix A is__________(up to 1 decimal place). Ans: 5.5 Sol:

Q. In the logic circuit shown in the figure, Y is given by (A) Y = ABCD                                              (B) Y = (A + B)(C + D) (C) Y = A + B + C + D                                  (D) Y = AB + CD Ans: Y = AB + CD

Q. The value of the directional derivative of the function 𝛷(𝑥, 𝑦, 𝑧) = 𝑥𝑦2 + 𝑦𝑧2 + 𝑧𝑥2 at the point (2, -1, 1) in the direction of the vector 𝐩 = 𝐢 + 2𝐣 + 2𝐤 is (A) 1                           (B) 0.95                      (C) 0.93                      (D) 0.9 Ans: 1 Sol:

Q. In the figure, the voltages are 𝑣1(𝑡) = 100cos(𝜔𝑡), 𝑣2(𝑡) = 100cos(𝜔𝑡 + 𝜋/18) and 𝑣3(𝑡) = 100cos(𝜔𝑡 + 𝜋/36). The circuit is in sinusoidal steady state, and 𝑅 << 𝜔𝐿. 𝑃1, 𝑃2 and 𝑃3 are the average power outputs. Which one of the following statements is true? (A) 𝑃1 = 𝑃2 = 𝑃3

Q. The graph of a network has 8 nodes and 5 independent loops. The number of branches of the graph is (A) 11                         (B) 12                         (C) 13                        (D) 14 Ans: 12