Cable -- Electrical Engineering (MCQ) questions and answers

1. Which of the following protects a cable against mechanical injury ?

A. Bedding
B. Sheath
C.Insulation
D. Armouring

2.Empire tape is

A.vulcanised rubber
B. impregnated paper
C.varnished cambric
D. none of the above

3. The thickness of the layer of insulation on the conductor, in cables, depends upon

A. reactive power
B. power factor
C.voltage
D.current carrying capacity

4. The insulating material for cables should

A. be acid proof
B. be non-inflammable
C. be non-hygroscopic
D. have all above properties

5.Which of the following insulation is used in cables ?

A. Varnished cambric
B.Rubber
C.Paper
D. Any of the above

6.The current carrying capacity of cables in D.C. is more thanthat in A.C. mainlydue to

A.absence of harmonics
B.non-existence of any stability limit
C.absence of ripples
D.smaller dielectric loss

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

A. unsheathed cables
B. armoured
C.PVC sheathed cables
D.all of the above

8.The minimum dielectric stress in a cable is at

A.armour
B.bedding
C. conductor surface
D.lead sheath

9.In single core cables armouring is not done to

A. avoid excessive sheath losses
B.make it flexible
C.either of the above
D. none of the above

10.The surge resistance of cable is

A. 100 ohms
B. 5 ohms
C. 50 ohms
D. 20 ohms

11.In the cables, the location of fault is usually found out by comparing

A.the resistance of the conductor
B. the inductance of conductors
C. all above parameters
D. the capacitances of insulated conductors

12.In capacitance grading of cables we use a ______ dielectric.

A. porous
B.hygroscopic
C. composite
D. homogeneous

13.The relative permittivity of rubber is

A. between 12 and 14
B.between 8 and 10
C.between 2 and 3
D.between 10 and 15

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

A. remains unchanged
B. becomes double
C.becomes one-half
D. becomes one-fourth

15. Solid type cables are considered unreliable beyond 66 kV because

A. insulation may melt due to higher temperature
B.skin effect dominates on the conductor
C. of corona loss between conductor and sheath material
D. there is a danger of breakdown of insulation due to the presence of voids

16. In cables the charging current

A.lags the voltage by 90°
B.leads the voltage by 180°
C. lags the voltage by 180°
D. leads the voltage by 90°

17. The electrostatic stress in underground cables is

A. maximum at the conductor and minimum at the sheath
B. zero at the conductor as well as on the sheath
C. minimum at the conductor and maximum at the sheath
D. same at the conductor and the sheath

18.The insulation of the cable decreases with

A. the increase in length of the insulation
B. the decrease in the length of the insulation
C.either (a) or (b)
D.none of the above

19.A cable carrying alternating current has

A.hysteresis and leakage losses only
B. hysteresis losses only
C. hysteresis, leakage and copper losses only
D. hysteresis, leakage, copper and friction losses

20.Underground cables are laid at sufficient depth

A. to minimise temperature stresses
B. to avoid being unearthed easily due to removal of soil
C. to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
D.for all of the above reasons