21. If the 3 − phase balanced source in the given figure delivers 1500 W at a leading power factor of 0.844, then the value of ZL is approximate __________
A. 90∠32.44°
B. 80∠32.44°
C. 80∠ − 32.44°
D. 90∠ − 32.44°
22. An RLC series circuit has a resistance R of 20Ω and a current which lags behind the applied voltage by 45°. If the voltage across the inductor is twice the voltage across the capacitor, the value of inductive resistance is ____________
A. 10 Ω
B. 20 Ω
C. 40 Ω
D. 60 Ω
23. In the Wheatstone bridge shown below, if the resistance in each arm is increased by 0.05%, then the value of Vout will be?
A. 50 mV
B. Zero
C. 5mV
D. 0.1mV
24. The voltage drop across a standard resistor of 0.2 Ω is balanced at 83 cm. The magnitude of the current, if the standard cell emf of 1.53 V is balanced at 42 m is ___________
A. 13.04 A
B. 10 A
C. 14.95 A
D. 12.56 A
25. The readings of polar type potentiometer are
I = 12.4∠27.5°
V = 31.5∠38.4°
Then the Reactance of the coil will be?
A. 2.51 Ω
B. 2.56 Ω
C. 2.54 Ω
D. 2.59 Ω
26. The simultaneous applications of signals x (t) and y (t) to the horizontal and vertical planes respectively, of an oscilloscope, produce a vertical figure of 8 displays. If P and Q are constants and x(t) = P sin (4t + 30), then y(t) is equal to _________
A. Q sin (4t – 30)
B. Q sin (2t + 15)
C. Q sin (8t + 60)
D. Q sin (4t + 30)
27. A resistor of 10 kΩ with a tolerance of 5% is connected in parallel with 5 kΩ resistors of 10% tolerance. The tolerance limit is _______
A. 9%
B. 12.4%
C. 8.33%
D. 7.87%
28. A 200/1 Current Transformer (CT) is wound with 400 turns on the secondary on a toroidal core. When it carries a current of 180 A on the primary, the ratio is found to be − 0.5%. If the number of secondary turns is reduced by 1, the new ratio error (in %) will be?
A. 0.0
B. − 0.5
C. − 1.0
D. − 2.0
29. In the Two wattmeter method of measuring power in a balanced three-phase circuit, one wattmeter shows zero and the other positive maximum. The load power factor is ___________
A. 0
B. 0.5
C. 0.866
D. 1.0
30. The meter constant of a single-phase, 230 V induction watt-meter is 600 rev/kW − h. The speed of the meter disc for a current of 15 A at 0.8 power factor lagging will be?
A. 30.3 rpm
B. 25.02 rpm
C. 27.6 rpm
D. 33.1 rpm