cables Mcqs
1. In case of three core flexible cable the colour of the neutral is_________?
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A. none of the above

B. brown

C. black

D. blue
2. In single core cables armouring is not done to________?
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A. either of the above

B. avoid excessive sheath losses

C. none of the above

D. make it flexible

3. Polyethylene has very poor dielectric and ageing properties
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A. Yes

B. No
4. The insulating material should have____________?
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A. low permittivity

B. all of the above

C. high resistivity

D. high dielectric strength

5. If the length of a cable is doubled, its capacitance____________?
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A. becomes one-half

B. becomes one-fourth

C. becomes double

D. remains unchanged

6. It is difficult to maintain oil filled cables____________?
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A. No

B. Yes
7. In cables the charging current__________?
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A. leads the voltage by 90

B. leads the voltage by 180

C. lags the voltage by 180

D. lags the voltage by 90

8. The disadvantage with paper as insulating material is____________?
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A. it has high capacitance

B. it is an organic material

C. it is hygroscopic

D. none of the above

9. The relative permittivity of rubber is____________?
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A. between 5 and 6

B. between 12 and 14

C. between 8 and 10

D. between 2 and 3
10. Rubber is most commonly used insulation in cables
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A. Yes

B. No

11. The breakdown voltage of a cable depends on_____________?
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A. working temperature

B. all of the above

C. presence of moisture

D. time of application of the voltage

12. Cables, generally used beyond 66 kV are___________?
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A. oil filled

B. belted

C. armoured

D. S.L. type

13. The insulating material for cables should____________?
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A. have all above properties

B. be non-inflammable

C. be acid proof

D. be non-hygroscopic

14. Empire tape is__________?
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A. impregnated paper

B. vulcanised rubber

C. none of the above

D. varnished cambric
15. Which of the following insulation is used in cables ?
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A. Rubber

B. Any of the above

C. Paper

D. Varnished cambric

16. cables are used for 132 kV lines____________?
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A. Super tension

B. High tension

C. Extra super voltage

D. Extra high tension

17. Underground cables are laid at sufficient depth___________?
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A. for all of the above reasons

B. to minimize the effect of shocks and vibrations due to gassing vehicles, etc

C. to minimise temperature stresses

D. to avoid being unearthed easily due to removal of soil

18. If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be_______________?
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A. 15 kV/mm

B. 30 kV/mm

C. 10 kV/mm

D. 5 kV/mm

19. Copper as conductor for cables is used as________?
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A. hard drawn

B. hardened and tempered

C. alloy with chromium

D. annealed
20. The electrostatic stress in underground cables is_________?
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A. none of the above

B. same at the conductor and the sheath

C. maximum at the conductor and minimum at the sheath

D. zero at the conductor as well as on the sheath

E. minimum at the conductor and maximum at the sheath

21. In congested areas where excavation is expensive and inconvenient draw in system of laying of underground cables is often adopted
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A. Yes

B. No

22. In the cables, sheaths are used to___________?
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A. provide enough strength

B. none of the above

C. prevent the moisture from entering the cable

D. provide proper insulation

23. PVC stands for____________?
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A. positive voltage conductor

B. pressed and varnished cloth

C. post varnish conductor

D. polyvinyl chloride

E. none of the above

24. The advantage of oil filled cables is_________?
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A. more perfect impregnation

B. smaller overall size

C. all of the above

D. no ionisation, oxidation and formation of voids

25. Conduit pipes are normally used to protect _______ cables
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A. PVC sheathed cables

B. all of the above

C. unsheathed cables

D. armoured

26. In capacitance grading a homogeneous dielectric is used
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A. Yes

B. No
27. The material for armouring on cable is usually__________?
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A. any of the above

B. none of the above

C. galvanised steel wire

D. steel tape

28. Which of the following protects a cable against mechanical injury___________?
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A. Armouring

B. Bedding

C. None of the above

D. Sheath

29. The surge resistance of cable is__________?
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A. 100 ohms

B. 50 ohms

C. 5 ohms

D. 20 ohms

30. A cable carrying alternating current has__________?
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A. hysteresis, leakage, copper and friction losses

B. hysteresis losses only

C. hysteresis and leakage losses only

D. hysteresis, leakage and copper losses only

31. Pressure cables are generally not used beyond__________?
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A. 66 kV

B. 33 kV

C. 132 kV

D. 11 kV

32. The breakdown of insulation of the cable can be avoided economically by the use of___________?
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A. inter-sheaths

B. insulating materials with different dielectric constants

C. both (A) and (B)

D. none of the above

33. The minimum dielectric stress in a cable is at_____________?
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A. conductor surface

B. bedding

C. lead sheath

D. armour

34. Solid type cables are considered unreliable beyond 66 kV because___________?
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A. skin effect dominates on the conductor

B. there is a danger of breakdown of insulation due to the presence of voids

C. of corona loss between conductor and sheath material

D. insulation may melt due to higher temperature

35. The thickness of metallic shielding on cables is usually_______________?
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A. 0.04 mm

B. 3 to 5 mm

C. 40 to 60 mm

D. 0.2 to 0.4 mm

36. Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ____________?
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A. Compressed SFe gas

B. Polyvinyle chloride

C. Impregnated paper

D. none of the above

E. Vulcanised rubber

37. The current carrying capacity of cables in D.C. is more than that in A.C. mainly due to__________?
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A. absence of harmonics

B. none of the above

C. non-existence of any stability limit

D. absence of ripples

E. smaller dielectric loss
38. Natural rubber is obtained from milky sap of tropical trees
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A. Yes

B. No

39. The metallic sheath may be made of lead or lead alloy or of aluminium ?
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A. Yes

B. No
40. Cables for 220 kV lines are invariably____________?
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A. none of the above

B. rubber insulated

C. compressed oil or compressed gas insulated

D. mica insulated

E. paper insulated

41. The thickness of the layer of insulation on the conductor, in cables, depends upon___________?
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A. voltage

B. reactive power

C. power factor

D. current carrying capacity

42. The intersheaths in the cables are used to_____________?
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A. avoid the requirement of good insulation

B. provide proper stress distribution

C. none of the above

D. minimize the stress

43. In the cables, the location of fault is usually found out by comparing____________?
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A. the resistance of the conductor

B. the capacitances of insulated conductors

C. all above parameters

D. the inductance of conductors

44. Low tension cables are generally used up to___________?
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A. 500 V

B. 1000 V

C. 700 V

D. 200 V

45. The advantage of cables over overhead transmission lines is___________?
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A. can be used in congested areas

B. can be used in high voltage circuits

C. low cost

D. easy maintenance

46. The bedding on a cable consists of____________?
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A. none of the above

B. any of the above

C. jute

D. hessian cloth

47. In a cable, the maximum stress under operating conditions is at___________?
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A. insulation layer

B. armour

C. sheath

D. conductor surface
48. If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be______________?
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A. 400 cm

B. 50 cm

C. 10 cm

D. 2 cm

49. In a cable immediately above metallic sheath ______ is provided
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A. none of the above

B. armouring

C. earthing connection

D. bedding
50. In a cable the voltage stress is maximum at____________?
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A. sheath

B. insulator

C. core of the conductor

D. surface of the conductor