About D.C. Generators

Following are some of the multiple choice questions on the D.C. Generators with answers that will help the students in developing their knowledge.

D.C. Generators MCQ

1. What is Superman's birth name?

  • nal-el
  • kal-el
  • mal-el
  • dal-el

2. Cables, generally used beyond 66 kV are

  • oil filled
  • S.L. type
  • belted
  • armoured

3. The metallic sheath may be made of lead or lead alloy or of aluminium.

  • Yes
  • No
  • none
  • none

4. Polyethylene has very poor dielectric and ageing properties.

  • Yes
  • No
  • none
  • none

5. Rubber is most commonly used insulation in cables.

  • Yes
  • No
  • none
  • none

6. Rubber is most commonly used insulation in cables.

  • Yes
  • No
  • none
  • none

7. Natural rubber is obtained from milky sap of tropical trees.

  • Yes
  • No
  • none
  • none

8. Natural rubber is obtained from milky sap of tropical trees.

  • Yes
  • No
  • none
  • none

9. In congested areas where excavation is expensive and inconvenient 'draw in system'of laying of underground cables is often adopted.

  • Yes
  • No
  • none
  • none

10. In congested areas where excavation is expensive and inconvenient 'draw in system'of laying of underground cables is often adopted.

  • Yes
  • No
  • none
  • none

11. In capacitance grading a homogeneous dielectric is used.

  • Yes
  • No
  • none
  • none

12. In capacitance grading a homogeneous dielectric is used.

  • Yes
  • No
  • none
  • none

13. The advantage of oil filled cables is

  • more perfect impregnation
  • smaller overall size
  • no ionisation, oxidation and formation of voids
  • all of the above

14. The advantage of oil filled cables is

  • more perfect impregnation
  • smaller overall size
  • no ionisation, oxidation and formation of voids
  • all of the above

15. The insulating material should have

  • low permittivity
  • high resistivity
  • high dielectric strength
  • all of the above

16. The insulating material should have

  • low permittivity
  • high resistivity
  • high dielectric strength
  • all of the above

17. Copper as conductor for cables is used as

  • annealed
  • hardened and tempered
  • hard drawn
  • alloy with chromium

18. If a power cable and a communication cable are to run parallel the minimum distancebetween the two, to avoid interference, should be

  • 2 cm
  • 10 cm
  • 50 cm
  • 400 cm

19. Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ?

  • Polyvinyle chloride
  • Vulcanised rubber
  • Impregnated paper
  • Compressed SFe gas

20. Cables for 220 kV lines are invariably

  • mica insulated
  • paper insulated
  • compressed oil or compressed gas insulated
  • rubber insulated

21. The thickness of metallic shielding on cables is usually

  • 0.04 mm
  • 0.2 to 0.4 mm
  • 3 to 5 mm
  • 40 to 60 mm

22. Underground cables are laid at sufficient depth

  • to minimise temperature stresses
  • to avoid being unearthed easily due to removal of soil
  • to minimise the effect of shocks and vibrations due to gassing vehicles, et
  • for all of the above reasons

23. Capacitance grading of cable implies

  • use of dielectrics of different permeabilities
  • grading according to capacitance of cables per km length
  • cables using single dielectric in different concentrations
  • capacitance required to be introduced at different lengths to counter the effect of inductance

24. In a cable the voltage stress is maximum at

  • sheath
  • insulator
  • surface of the conductor
  • core of the conductor

25. In a cable the voltage stress is maximum at

  • sheath
  • insulator
  • surface of the conductor
  • core of the conductor

26. A cable carrying alternating current has

  • hysteresis losses only
  • hysteresis and leakage losses only
  • hysteresis, leakage and copper losses only
  • hysteresis, leakage, copper and friction losses

27. The insulation of the cable decreases with

  • the increase in length of the insulation
  • the decrease in the length of the insulation
  • either (a) or (b)
  • none of the above

28. The breakdown of insulation of the cable can be avoided economically by the use of

  • inter-sheaths
  • insulating materials with different dielectric constants
  • both (a) and (b)
  • none of the above

29. The electrostatic stress in underground cables is

  • same at the conductor and the sheath
  • minimum at the conductor and maximum at the sheath
  • maximum at the conductor and minimum at the sheath
  • zero at the conductor as well as on the sheath

30. If the length of a cable is doubled, its capacitance

  • becomes one-fourth
  • becomes one-half
  • becomes double
  • remains unchanged

31. The current carrying capacity of cables in D.C. is more thanthat in A.C. mainly due to

  • absence of harmonics
  • non-existence of any stability limit
  • smaller dielectric loss
  • absence of ripples

32. In case of three core flexible cable the colour of the neutral is

  • blue
  • black
  • brown
  • none of the above

33. Cables are used for 132 kV lines.

  • High tension
  • Super tension
  • Extra high tension
  • Extra super voltage

34. Conduit pipes are normally used to protect _____ cables.

  • unsheathed cables
  • armoured
  • PVC sheathed cables
  • all of the above

35. The minimum dielectric stress in a cable is at

  • armour
  • bedding
  • conductor surface
  • lead sheath

36. In single core cables armouring is not done to

  • avoid excessive sheath losses
  • make it flexible
  • either of the above
  • none of the above

37. Dielectric strength of rubber is around

  • 5 kV/mm
  • 15 kV/mm
  • 30 kV/mm
  • 200 kV/mm

38. Low tension cables are generally used upto

  • 200 V
  • 500 V
  • 700 V
  • 1000 V

39. In a cable, the maximum stress under operating conditions is at

  • insulation layer
  • sheath
  • armour
  • conductor surface

40. High tension cables are generally used upto

  • 11kV
  • 33kV
  • 66 kV
  • 132 kV

41. High tension cables are generally used upto

  • 11kV
  • 33kV
  • 66 kV
  • 132 kV

42. The surge resistance of cable is

  • 5 ohms
  • 20 ohms
  • 50 ohms
  • 100 ohms

43. The surge resistance of cable is

  • 5 ohms
  • 20 ohms
  • 50 ohms
  • 100 ohms

44. In the cables, sheaths are used to

  • prevent the moisture from entering the cable
  • provide enough strength
  • provide proper insulation
  • none of the above

45. 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

  • one half
  • double
  • four times
  • none of the above

46. If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then thedielectric strength of insulation should be

  • 5 kV/mm
  • 10 kV/mm
  • 15 kV/mm
  • 30 kV/mm

47. In the cables, sheaths are used to

  • prevent the moisture from entering the cable
  • provide enough strength
  • provide proper insulation
  • none of the above

48. In cables the charging current

  • lags the voltage by 90°
  • leads the voltage by 90°
  • lags the voltage by 180°
  • leads the voltage by 180°

49. The intersheaths in the cables are used to

  • minimize the stress
  • avoid the requirement of good insulation
  • provide proper stress distribution
  • none of the above

50. The intersheaths in the cables are used to

  • minimize the stress
  • avoid the requirement of good insulation
  • provide proper stress distribution
  • none of the above

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