Correct : A. only if the resistance of the field circuit is less than critical value
3. The terminal voltage of a series generator is 150 V when the load current is 5 A. If the
load current is increased to 10 A, the terminal voltage will be
Correct : C. greater than 150 V
4. The open circuit voltage of a compound generator is 250 V. At full load the terminal
voltage
Correct : C. may be greater or less than 250 V
5. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be
Correct : B. 267.5 V
6. The essential condition for parallel operation of two D.C. generators is that they have
Correct : C. the same drooping voltage charac-teristics
7. When two D.C. generators are running in parallel an equilizer bar is used
Correct : D. so that the two identical machines will pass approximately equal currents to the load
8. With a D.C. generator which of the following regulation is preferred ?
Correct : D. 1% regulation
9. Which generator would you prefer for feeding long D.C. transmission lines ?
Correct : C. Over compound generator
10. In a D.C. generator the critical resistance can be increased by
Correct : C. increasing its speed
11. The number of armature parallel paths in a two-pole D.C. generator having duplex lap
winding is
Correct : B. 4
12. For both lap and wave windings, there are as many commutator bars as the number of
Correct : C. winding elements
13. The series field of a short-shunt D.C. generator is excited by
Correct : D. load current
14. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C.
generator is approximately
Correct : D. 5 percent
15. Shunt generators are most suited for stable parallel operation because of their
Correct : C. drooping voltage characteristics
16. The main factor which leads to unstable parallel operation of flat and over
compounded generators is
Correct : A. their rising voltage characteristics
17. If a self excited D.C. generator after being installed, fails to build up on its first trial run,
the first thing to do is to
Correct : A. reverse the field connections
18. The insulating material for a cable should have
Correct : D. all of the above
19. Which of the following protects a cable against mechanical injury ?
Correct : C. Armouring
20. Which of the following insulation is used in cables ?
Correct : D. Any of the above
21. Empire tape is
Correct : A. varnished cambric
22. The thickness of the layer of insulation on the conductor, in cables, depends upon
Correct : C. voltage
23. The bedding on a cable consists of
Correct : C. any of the above
24. The insulating material for cables should
Correct : D. have all above properties
25. In a cable immediately above metallic sheath _____ is provided.
Correct : B. bedding
26. The current carrying capacity of cables in D.C. is more thanthat in A.C. mainly due to
Correct : C. smaller dielectric loss
27. In case of three core flexible cable the colour of the neutral is
Correct : A. blue
28. cables are used for 132 kV lines.
Correct : D. Extra super voltage
29. Conduit pipes are normally used to protect _____ cables.
Correct : A. unsheathed cables
30. The minimum dielectric stress in a cable is at
Correct : D. lead sheath
31. In single core cables armouring is not done to
Correct : A. avoid excessive sheath losses
32. Dielectric strength of rubber is around
Correct : C. 30 kV/mm
33. Low tension cables are generally used upto
Correct : D. 1000 V
34. In a cable, the maximum stress under operating conditions is at
Correct : D. conductor surface
35. High tension cables are generally used upto
Correct : A. 11kV
36. The surge resistance of cable is
Correct : C. 50 ohms
37. PVC stands for
Correct : A. polyvinyl chloride
38. In the cables, the location of fault is usually found out by comparing
Correct : C. the capacitances of insulated conductors
39. In capacitance grading of cables we use a ______ dielectric.
Correct : A. composite
40. Pressure cables are generally not used beyond
Correct : C. 66 kV
41. The material for armouring on cable is usually
Correct : C. any of the above
42. Cables, generally used beyond 66 kV are
Correct : A. oil filled
43. The relative permittivity of rubber is
Correct : A. between 2 and 3
44. Solid type cables are considered unreliable beyond 66 kV because
Correct : D. there is a danger of breakdown of insulation due to the presence of voids
45. If the length of a cable is doubled, its capacitance
Correct : C. becomes double
46. In cables the charging current
Correct : B. leads the voltage by 90°
47. A certain cable has an insulation of relative permittivity 4. If the insulation is replaced by one of relative permittivity 2, the capacitance of the cable will become
Correct : A. one half
48. If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the
dielectric strength of insulation should be
Correct : B. 10 kV/mm
49. In the cables, sheaths are used to
Correct : A. prevent the moisture from entering the cable
50. The intersheaths in the cables are used to
Correct : C. provide proper stress distribution
51. The electrostatic stress in underground cables is
Correct : C. maximum at the conductor and minimum at the sheath
52. The breakdown of insulation of the cable can be avoided economically by the use of
Correct : C. both (a) and (b)
53. The insulation of the cable decreases with
Correct : A. the increase in length of the insulation
54. A cable carrying alternating current has
Correct : B. hysteresis and leakage losses only
55. In a cable the voltage stress is maximum at
Correct : D. core of the conductor
56. Capacitance grading of cable implies
Correct : A. use of dielectrics of different permeabilities
57. Underground cables are laid at sufficient depth
Correct : C. to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
58. The advantage of cables over overhead transmission lines is
Correct : C. can be used in congested areas
59. The thickness of metallic shielding on cables is usually
Correct : A. 0.04 mm
60. Cables for 220 kV lines are invariably
Correct : C. compressed oil or compressed gas insulated
61. Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ?
Correct : D. Compressed SFe gas
62. If a power cable and a communication cable are to run parallel the minimum distance
between the two, to avoid interference, should be
Correct : C. 50 cm
63. Copper as conductor for cables is used as
Correct : A. annealed
64. The insulating material should have
Correct : D. all of the above
65. The advantage of oil filled cables is
Correct : D. all of the above
66. The disadvantage with paper as insulating material is
Correct : A. it is hygroscopic
67. The breakdown voltage of a cable depends on
Correct : D. all of the above
68. In capacitance grading a homogeneous dielectric is used.
Correct : B. No
69. In congested areas where excavation is expensive and inconvenient 'draw in system'
of laying of underground cables is often adopted.
Correct : A. Yes
70. Natural rubber is obtained from milky sap of tropical trees.
Correct : A. Yes
71. Rubber is most commonly used insulation in cables.
Correct : A. Yes
72. Polyethylene has very poor dielectric and ageing properties.
Correct : B. No
73. The metallic sheath may be made of lead or lead alloy or of aluminium.