IOCL Junior Operator MCQ Part-8 || IOCL Junior Operator General Science Questions and Answers51. Why are single-core cables not usually armoured?1 . To reduce manufacturing costs 2 . To avoid excessive sheath losses 3 . To increase flexibility 4 . To improve conductivity Answer and SolutionAnswer: "To avoid excessive sheath losses " Single-core cables are not usually armoured to avoid excessive sheath losses. Armouring can introduce additional losses, which are undesirable in low-voltage applications. The lead sheath acts as a moisture barrier, protecting the insulation from environmental damage. Discuss52. For voltages up to 66 kV, what type of cable is generally preferred for 3-phase service?1 . Three-core cables 2 . Pressure cables 3 . Single-core cables 4 . Extra super voltage cables Answer and SolutionAnswer: "Three-core cables " For 3-phase service up to 66 KV, three-core cables are preferred due to economic reasons. These cables are more cost-effective for delivering 3-phase power at medium to high voltages. Three-core cables are more economical for these voltages due to reduced material and installation costs. Discuss53. What is the typical voltage range for belted cables?1 . Up to 11 KV 2 . Up to 22 KV 3 . Both 1 and 2 4 . From 22 KV to 33 KV Answer and SolutionAnswer: "Both 1 and 2 "Belted cables are typically used for voltages up to 11 KV. However, in extraordinary cases, their use may be extended up to 22 KV. Discuss54. What material is used to insulate the cores in a belted cable?1 . Impregnated paper 2 . Fibrous insulating material (jute etc.) 3 . Lead sheath 4 . Paper belt Answer and SolutionAnswer: "Impregnated paper "The cores in a belted cable are insulated from each other by layers of impregnated paper. This material provides effective electrical insulation. Discuss55. What is the purpose of the paper belt in a belted cable?1 . To provide additional insulation 2 . To fill the gap between the insulated cores 3 . To protect against mechanical injury 4 . To prevent the ingress of moisture Answer and SolutionAnswer: "To provide additional insulation "The paper belt, made of impregnated paper tape, is wound around the grouped insulated cores to provide additional insulation. It helps in enhancing the overall insulation properties of the cable. Discuss56. What material is used to fill the gap between the insulated cores in a belted cable?1 . Impregnated paper 2 . Lead sheath 3 . Paper belt 4 . Fibrous insulating material (jute etc.) Answer and SolutionAnswer: "Fibrous insulating material (jute etc.) " The gap between the insulated cores in a belted cable is filled with fibrous insulating material such as jute. This material helps in maintaining the structural integrity and insulation properties of the cable. Discuss57. What is the purpose of the lead sheath in a belted cable?1 . To provide additional insulation 2 . To prevent electromagnetic interference 3 . To protect against mechanical injury and ingress of moisture 4 . To fill the gap between the insulated cores Answer and SolutionAnswer: "To protect against mechanical injury and ingress of moisture " The lead sheath in a belted cable is used to protect the cable against mechanical injury and the ingress of moisture. It ensures the durability and reliability of the cable in various environmental conditions. Discuss58. Why is the belted type construction suitable only for low and medium voltages?1 . Because of the radial electrostatic stresses 2 . Because of the tangential electrostatic stresses 3 . Because of the mechanical stresses 4 . Because of the thermal stresses Answer and SolutionAnswer: "Because of the radial electrostatic stresses " The belted type construction is suitable for low and medium voltages because it handles radial i.e., across the insulation (or outward) electrical stresses well. At higher voltages, there are additional stresses that act sideways through the insulation layers, which can cause problems like overheating and insulation failure. This sideways stress ( tangential stresses) is harder for the belted construction to manage, making it less suitable for high-voltage applications. Discuss59. What is the typical voltage range for screened cables?1 . Up to 11 KV 2 . Up to 33 KV 3 . Up to 66 KV 4 . Beyond 66 KV Answer and SolutionAnswer: "Up to 33 KV "Screened cables are typically used for voltages up to 33 KV. However, in particular cases, their use may be extended to operating voltages up to 66 KV. Discuss60. What are the two principal types of screened cables?1 . H-type and S.L. type 2 . Belted and Screened 3 . Single-core and Multi-core 4 . Pressure and Solid type Answer and SolutionAnswer: "H-type and S.L. type "The two principal types of screened cables are H-type and S.L. (Separate Lead) type cables. Discuss123456789
