NCL PREVIOUS YEAR PAPER 2020 -Written test for the Post of Technician Electrician , G4E , Gyan4ele by lipun panigrahi
1. In a Power Plant a reserve generating capacity which is in operation but not in service, is known as:
A) Hot reserve
B) Cold reserve
D) Firm power
Ans:- A
2. Which Lightening stroke is most dangerous:
B)Direct stroke on ground wire
C)Direct stroke on line conductor
D)Indirect stroke on conductor
Ans:- C
3. Transmission efficiency increases as:
A)Voltage and Power factor both increase
B)Voltage and Power factor both decrease
C)Voltage increase but power factor decrease
D)Voltage decrease but power factor increase
Ans:- A
4.When Alternating Current passes through a conductor:
A) It remains uniformly distributed throughout the section of conductor
B) Portion of conductor near the surface carries more current as compared to the core
C) Portion of conductor near the surface carries less current as compared to the core
D)Entire current passes through the core of the conductor
Ans:- B
5. The effective resistance of a conductor will be the same as “ohmic resistance”, when:
A) Current is in true sine wave form
B) Voltage is low
C) Power factor is unity
D)Current is uniformly distributed in the conductor cross section
Ans:- D
6. Skin effect depends on:
A) Size of the conductor
B) Frequency of the current
C) Resistivity of the conductor material
D) All of the above
Ans:- D
7. In overhead transmission lines the effect of the capacitance can be neglected when the length of the line is less than:
A) 200 km
B) 160 km
C) 100 km
D) 80 km
Ans:- D
8. The surge impedance for overhead line is taken as:
A)10 – 20 ohms
B) 50 – 60 ohms
C)100 – 200 ohms
D)1000 – 2000 ohms
Ans:- C
9. Pin insulators are normally used up to voltage of about:
A) 100 KV
B) 66 KV
C) 33 KV
D) 25 KV
Ans:- C
10. Corona usually occurs when the electrostatic stress in the air around the conductor succeeds:
A) 30 KV (maximum value)/cm
B) 22 KV (maximum value)/cm
C) 11 KV (rms value)/cm
D) 6.6 KV (rms value)/cm
Ans:- A
11. When the power is to be transmitted over a distance of 500 km, the transmission voltage should be in the range of:
A) 33 KV – 66 KV
B) 66 KV – 100 KV
C)110 KV – 150 KV
D) 150 KV – 220 KV
Ans:- D
12. Litz wires are used for intermediate frequencies, to overcome:
A)Corona effect
B)Skin effect
C)Radio interference
D)All of the above
Ans:- B
13. In order to reduce skin effect at UHF:
A) Conductors are painted
B) Conductors are anodized
C) Copper tubes with silver plating are used
D) Copper rods with silver plating are used
Ans:- C
14. A Relay used on long transmission lines is:
A) Mho’s Relay
B) Reactance Relay
C)Impedance Relay
D) No Relay is used
Ans:- A
15. The function of steel wire in a ACSR conductor is:
A)To take care of surges
B)To prevent corona
C)To reduce inductance and hence improve Power factor
D)To provide additional mechanical strength
Ans:- D
16. Boosters are basically:
A) Inductors
B) Capacitors
C) Transformers
D) Synchronous motors
Ans:- C
17. Which of the following short circuit is the most dangerous:
A)Line to line short circuit
B)Dead short circuit
C)Line to ground short circuit
D)Line to line and ground short circuit
Ans:- B
18. In a transmission line, if a booster transformer are to be used, preferred location will be:
A)At the receiving end
B) At the sending end
C) At the intermediate point
D) Anywhere in the line
Ans:- C
19. Insulators for high voltage applications are tested for:
A) Power frequency tests
B) Impulse tests
C)Both A and B
D) None of the above
Ans:- C
20. The electrical breakdown strength of insulating materials depends on:
A) Nature of applied voltage
B) Imperfections in dielectric material
C) Pressure, temperature and humidity
D) All of the above
Ans:- D
21. Which of the following gas has been used as insulating medium in electric appliances?
A) Nitrogen
B) Carbon dioxide
C)Sulphur hexafluoride
D) Freon
Ans:- C
22. Electromechanical breakdown of solid insulating materials occurs due to:
A) Magnetic hum
B) Vibrations
C)Mechanical stresses produced by the electric field
D)Electrical stresses produced by the voltage fluctuations
Ans:- C
23. 3 A 3300/250 V, 50 Hz single phase transformer is built on a core having an effective cross – sectional area of 125 cm2 and to turn on the low voltage winding. Then the number of turns on the high voltage winding is:
A)663
B) 924
C)1848
D) 462
Ans:- B
24. A transformer with 800 primary turns and 200 secondary turns is supplied from a 100 V A.C. supply. Calculate the Secondary Voltage:
A)400 V
B) 25 V
C)250 V
D) 40 V
Ans:- B
25. A transformer with 800 primary turns and 200 secondary turns is supplied from a 100 V A.C. supply. Calculate the Volts per turn:
A)0.25
B) 8
C) 4
D) 0.125
Ans:- D
26. A 25 KVA transformer has a voltage ratio of 3300/400 V. Calculate the Primary and Secondary Currents:
A)16 A, 132 A
B) 7.58 A, 62.5 A
C) 13.2 A, 160 A
D) 6.25 A, 75.8 A
Ans:- B
27. Which of the following is minimized by laminating the core of a transformer:
A)Hysteresis loss
B) Eddy Current loss
C)Heat loss
D) All of the above
Ans:- B
28. Iron loss in transformer occurs in:
A)Core
B) Winding
C)Insulating Oil
D)Main Body
Ans:- A
29. Under no load condition, which of the following loss is negligible?
A)Hysteresis loss
B)Eddy Current loss
C)Copper loss
D)All losses have same magnitude
Ans:- C
30. Copper loss in a transformer occurs in
A) Core
B) Winding
C) Main Body
D) Bushing
Ans:- B
31. For a transformer, the condition for maximum efficiency is:
A) Hysteresis loss = Eddy Current loss
B) Core loss = Hysteresis loss
C) Copper loss = Iron loss
D) Total loss = ⅔ x Copper loss
Ans:- C
32. Eddy Current losses in a transformer core can be reduced by:
A)Reducing the thickness of laminations
B)Increasing the thickness of laminations
C)Increasing the air gap in the magnetic circuit
D)Reducing the air gap in the magnetic circuit
Ans:- A
33. In a transformer, the magnetic coupling between the Primary and Secondary Circuit can be increased by:
A) Increasing the number of turns
B) Using soft material for windings
C) Using the magnetic core of low reluctance
D) Using transformer oil of better quality
Ans:- C
34. Which loss in a transformer varies significantly with load?
A)Hysteresis loss
B) Eddy Current loss
C)Copper loss
D) Core loss
Ans:- C
35. The Power factor in a transformer:
A) Is always unity
B)Is always leading
C)Is always lagging
D)Depends on the power factor of the load
Ans:- D
36. At no load, the current taken by a transformer:
A) Lags behind the applied voltage by 800
B) Lags behind the applied voltage by 500
C) Leads the applied voltage by 500
D) Leads the applied voltage by 800
Ans:- A
37. A short circuit test on a transformer gives:
A) Copper losses at full load
B) Copper losses at half load
C) Iron losses at any load
D) Sum of iron losses and copper losses
Ans:- A
38. A step up transformer increases:
A)Power
B) Power factor
C)Voltage
D) Frequency
Ans:- C
39. In a step down transformer:
A)Secondary turns are less than Primary turns
B)Secondary power is less than Primary power
C)Phase shift is always 1800
D)Secondary current is always more than Primary current
Ans:- A
40.In high frequency transformers:
A) Carbon cores are used
B) Wooden cores are used
C) Ferrite cores are used
D) Aluminum cores are used
Ans:- C
41. Open circuit test on a transformer yields:
A) Core losses
B) Copper losses
C) Sum of core and copper losses
D)Leakage of reactance
Ans:- A
42. The leakage flux in a transformer depends upon:
A) Load current
B)Load current and voltage
C)Load current, voltage and frequency
D) Load current, voltage, frequency and power factor
Ans:- A
43. Which of the following is not a routine test on transformer?
A) Polarity test
B)Radio interference test
C)Core insulation voltage test
D)Impedance test
Ans:- B
44. In a transformer, if peak voltage is fed to primary:
A) The iron loss will be less
B) The iron loss will be more
C) The copper loss will be less
D) The windage loss will be more
Ans:- A
45. The function of transformer oil in a transformer is:
A) To provide insulation and cooling
B) To provide protection against lightening
C) To provide protection against short circuit
D) To lubricate the moving parts
Ans:- A
46. Buchholz relay is used on:
A) Air cooled transformers
B) Oil cooled transformers
C)Welding transformers
D)Furnace transformers
Ans:- B
47. In a distribution transformer, normally:
A) Core losses are equal to copper losses
B) Core losses are more than copper losses
C) Core losses are less than copper losses
D) Core losses are half of the copper losses
Ans:- C
48. A Buchholz relay will operate in a transformer whenever there is:
A) Large internal fault
B) Saturation of magnetic circuit
C) Overload
D) Any of the above
Ans:- A
49. A transformer can have zero voltage regulation at:
A) Zero power factor
B)Lagging power factor
C)Leading power factor
D)Unity power factor
Ans:- C
50. An autotransformer is used:
A) When operator is not available
B) When copper losses are to be reduced
C) When higher efficiency is desired
D) When the transformation ratio is small
Ans:- D
51. If the transformer core is made of copper:
A) Copper loss will be less
B) Eddy current loss will be more
C) Hysteresis loss will be more
D) None of the above
Ans:- B
52. The efficiency of the two identical transformers under load conditions can be determined by:
A)Back to back test
B)Open circuit test
C)Short circuit test
D)Any of the above
Ans:- A
53. If a transformer core is made of copper and coils are made up of steel wire, then:
A) Magnetizing current will be reduced
B) Copper loss in the winding will be more
C) Eddy current loss will be less
D) All of the above
Ans:- B
54. Which of the following loss in a transformer is zero even at full load?
A) Eddy current loss
B)Hysteresis loss
C)Core loss
D)Friction loss
Ans:- D
55. In Scott connections the main transformer has centre tap on:
A) Primary windings
B)Secondary windings
C)Both primary and secondary windings
D)None of the above
Ans:- C
56. A Tap changer is used on a transformer for:
A)Adjustment in primary voltage
B)Adjustment in secondary voltage
C)Adjustment in both primary and secondary voltage
D)Adjustment in power factor
Ans:- B
57. Over currents in a transformer affect:
A) Insulation life
B)Temperature rise
C)Mechanical stress
D)All of the above
Ans:- D
58. A current transformer can be used with which of the following instruments?
A)Ammeter
B)Wattmeter
C)Watt hour meter
D)Any of the above
Ans:- D
59. Which of the following is not a fitting on the transformer?
A)Breather
B)Conservator
C)Buchholz relay
D)Commutator
Ans:- D
60. The reactance of the transformer depends on:
A)Size of core
B) Size of tank
C)Leakage flux
D)All of the above
Ans:- C
61. If the frequency of supply voltage is doubled, which loss will increase?
A)Eddy current loss
B)Hysteresis loss
C)Copper loss
D)None of the above
Ans:- A
62. In which of the following transformer, part of primary winding also serves as the secondary winding?
A)Step up transformer
B)Current transformer
C)Potential transformer
D)Autotransformer
Ans:- D
63. Which of the following frequencies has the longest period:
A)1 Hz
B) 10 Hz
C)1 KHz
D)10 KHz
Ans:- A
64. Which device convert AC into DC:
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