7 / 31 ACSR Q18. The current through a series RL circuit is when excited by a unit impulse voltage. The values of R and L are respectively, 8,4 4,2 2,4 1,4 Q19. The critical frequency of an ionosphere is 10 MHz. What is the maximum launching angle from the horizon for which a 20 MHz wave will be reflected by the layer? 0° 30° 45° 90° Q20. A half- wave thyristor converter supplies a purely inductive load, as shown in Figure. If the triggering angle of the thyristor is 120°, the extinction angle. 240° 180° 200° 120° Q21. In the ac bridge in the figure Z₁ = 450 ohm, Z₂ = (300-j600) ohm, Z₃ = (200+j100) ohm. The of unknown impedance Z₄ at balance is (100+j150) ohm (100-j150) ohm (300+j150) ohm (0 +j150) ohm. Q22. Consider the following statements regarding a firs t order system with a proportional (P) controller which exhibits an offset to a step input: Increase the gain of the P controller. Add derivative mode. Add integral mode.
7 / 31 ACSR Q18. The current through a series RL circuit is when excited by a unit impulse voltage. The values of R and L are respectively, 8,4 4,2 2,4 1,4 Q19. The critical frequency of an ionosphere is 10 MHz. What is the maximum launching angle from the horizon for which a 20 MHz wave will be reflected by the layer? 0° 30° 45° 90° Q20. A half- wave thyristor converter supplies a purely inductive load, as shown in Figure. If the triggering angle of the thyristor is 120°, the extinction angle. 240° 180° 200° 120° Q21. In the ac bridge in the figure Z₁ = 450 ohm, Z₂ = (300-j600) ohm, Z₃ = (200+j100) ohm. The of unknown impedance Z₄ at balance is (100+j150) ohm (100-j150) ohm (300+j150) ohm (0 +j150) ohm. Q22. Consider the following statements regarding a firs t order system with a proportional (P) controller which exhibits an offset to a step input: Increase the gain of the P controller. Add derivative mode. Add integral mode.