SSC Electrical Junior engineer exam paper 2011 morning
को
लिंक पाएं
Facebook
X
Pinterest
ईमेल
दूसरे ऐप
1. If in an R-L-C series circuit the current lags the applied
voltage by 60 than ?
...
Answer is B) If current lags the applied voltage by 60, We know XL is greater than XC
so XL-XC = Xl
tan60° = Xl/R = (XL – Xc)/R
√3R = (XL – Xc)
.
2. A lossy capacitor with loss angle of 0.01 radian, draws a current
of 0.5 A when supplied at 1000 V from a sinusoidal voltage source. The
active power consumed by the capacitor is ?
...
Answer is A) Loss angle = 0.01 radian
θL = 0.01 x 180/π = 0.57 ———- (Converting radian into degree)
P.F. angle = 90 – 0.57 = 89.43
Active power consumed = V I cosθ
= 1000 × 0.5 × cos(89.427)
= 4.999 ≅ 5.
3. An ac voltage source with an internal impedance Z1 is connected to
a load of impedance Z2. For maximum power transfer to the load, the
condition is ?
...
Answer is D) For maximum power transfer, input Impedance must be equal to the conjugate of output Impedance.
As we know that The impedance of an input of something to which a signal is applied is a measure of how much power that input will tend to draw (from a given output voltage). This impedance is known as the load impedance.
Therefore Z2 = Z1*.
4. The resonant frequency of the ac series circuit shown in figure
given below, in Hz, is ?
...
Answer is A) When the coils are joined in series with additive flux the equivalent inductance is
Leq = L1 + L2 – 2M = 2 + 2 – 2 x 1 = 2H
The resonant frequency of the AC series circuit in Herz is given as
F = 1/2π√LC
Where L = 2H & C = 2F
F = 1/2π√LC = 1/2π√4
= 1/4π.
5. A current wave starts at zero, rises instantaneously then remains
at a valueof 20A for 10 sec, thendecreases instantaneously, remaining at
a value of –10A for 20 sec, and then repeats this cycle. The rms volue
of the wave is ?
...
Answer is D) Watch the Video.
6. Two incandescent bulbs of rating 230 V, 100W and 230V, 500 W are
connected in parallel across the mains. As a result, what will happen ?
...
Answer is B) Watch the Video.
7. In two wattmeter method of measurement of three-phase powerof a
balanced load, if both the wattmeters indicate the same reading, then
the power factor of the load is ?
...
Answer is C) Watch the Video.
8. Measurement of……is affected by the presence of thermo-emf in the
measuring circuit– ?
...
Answer is A) Watch the Video.
9. The response time of an indicating instrument is determined by
its– ?
...
Answer is B) Watch the Video.
10. SThe ratio of thereading of two wattmetters connected to measure
active power ina balanced 3-phase load is 2: 1 The power factor of the
load is ?
...
Answer is A) Watch the Video.
11. The power input to a 3-phase, 50Hz, 400V, 4- pole induction motor
is 60KW and its stator losses are 1 KW. If this motor is running at 4%
slip, the rotor copper loss is– ?
...
Answer is B) Watch the Video.
12. In a transformer, the core loss is found to be 46W a 50 Hz and is
80 W a 70 Hz, both losses being measured at the same peak flux density.
The hysteresis loss and eddy current loss at 60Hz is–?
...
Answer is D) Watch the Video.
13. The voltage wave given by v=4 cost ?t produces a current wave
i=1.5 cos ?t-2.598 Sin ?t in a circuit. The current wave ?
...
Answer is A) Watch the Video.
14. The damping in D' Arsonval galvanometer is obtained by– ?
...
Answer is B) Watch the Video.
15. If ? represent deflection of pointer, the controlling torque in
a spring-controlled indicating instrument is proportional to– ?
...
Answer is A) Watch the Video.
16. The range of a dc milliameter can be extended by using a– ?
...
Answer is B) Watch the Video.
17. For use in ac circuits, potential coil circuit of electrodynamic
wattmeter should be purely– ?
...
Answer is A) Watch the Video.
18. A dc shunt generator builds upto 230V. Other conditions remaining
same, if only the residual magnetism of the original machine is
reversed, the voltage to which the generator will build up is– ?
...
Answer is C) Watch the Video.
19. A 100 kVA single phase transformer exhibits maximum efficiency at
80% of full load and the total loss in the transformer under this
condition is 1000W. The ohmic lossea at full load will be– ?
...
Answer is A) Watch the Video.
20. If a 3-phase induction motor hums during starting up, the
probable cause could be– ?
...
Answer is D) Watch the Video.
21. In a 3-phase synchronous generator, the stator winding is
connected in star, because a delta connection would– ?
...
Answer is B) Watch the Video.
22. A 40 kV/A transformer has a core loss of 400 W and full load
copper loss of 800W. The fraction of rated load at maximum efficiency
is– ?
...
Answer is C) Watch the Video.
23. The torque developed in a dc series motor in unsaturated magnetic
circuit condition is– ?
...
Answer is C) Watch the Video.
24. A 220 V shunt motor develops a torque of 60 Nm at an armature
current of 10A. The torque developed when the armature current is 20A,
is– ?
...
Answer is D) Watch the Video.
25. An alternator has rated field current of 3A. It is developing 180
V at a field current of 1.5A at rated speed. If its field current is
made 3A at rated speed, then the generated voltage would be– ?
...
Answer is A) Watch the Video.
26. High voltage transmission efficiency is in the range of– ?
...
Answer is D) Watch the Video.
27. In which of the following industries, are all the motors totally
enclosed and moisture proof ?
...
Answer is C) Watch the Video.
28. An 4 pole induction motor have 0.03 slip and connected to 50 Hz
source than find speed of rotating magnetic field and rotor frequiency
?
...
Answer is C) Watch the Video.
29. In suspension type insulator the potential drop is– ?
...
Answer is A) Watch the Video.
30. Of the following water turbines, which is not a reaction turbine
?
...
Answer is A) Watch the Video.
31. Sheaths are used in underground cables to– ?
...
Answer is C) Watch the Video.
32. If the frequency of a transmission system is changed from 50Hz to
100Hz, the string efficiency– ?
...
Answer is B) Watch the Video.
33. The power station where coal is used as a fuel is called– ?
...
Answer is B) Watch the Video.
34. Making capacity of a circuit breaker is equal to– ?
...
Answer is A) Watch the Video.
35. A string insulator has 4 units. The voltage across the bottom-
most unit is 33.33% of the total voltage. Its string efficiency is– ?
...
Answer is D) Watch the Video.
36. Load factor for the load duration curve shown below is ?
...
Answer is B) Watch the Video.
37. Resistance switching is normally employed in ?
...
Answer is D) Watch the Video.
38. Which one is the disadvantage of oil when used as an are-
extinguishing medium in the oil circuit breaker ?
...
Answer is A) Watch the Video.
39. If the discharge voltage of a thyrite arrester is 373kV rms and
the rated voltage is 211kVrms, the discharge factor of the arrester is
?
...
Answer is D) Watch the Video.
40. During are extinction SF6 gets ?
...
Answer is A) Watch the Video.
41. Sparking between the contacts of a circuit breaker can be reduced
by inserting ?
...
Answer is A) Watch the Video.
42. If the inductance and capacitance of a power system are
respectively 1 H and 0.01 µF and the instantaneous value of interrupted
current is 10A, then the voltage across the breaker contacts will be ?
...
Answer is D) Watch the Video.
43. Which of the following materials for heating element should be
selected if a furnace is to be used for heating upto temperature around
1500 C ?
...
Answer is C) Watch the Video.
44. The type of d.c. generator used for are welding should be a ?
...
Answer is B) Watch the Video.
45. A transistor is operating in common emitter mode as shown in
figure given below. The voltage VCE is ?
...
Answer is C) Watch the Video.
46. By increasing the transmission voltage to double of its original
value the same power can be dispatched keeping the line loss ?
...
Answer is D) Watch the Video.
47. Which of the following is true ?
...
Answer is D) Watch the Video.
48. An electric load consumes 17.32kW at a power factor of 0.707
(lagging). For changing the load power factor to 0.866b (lagging), the
capacitor that is to be connected in parallel with the load, should draw
?
...
Answer is A) Watch the Video.
49. The most appropriate way of mitigating the problem of
interference between power line and communication line is to ?
टिप्पणियाँ
एक टिप्पणी भेजें