Electric Cables: Multiple Choice Questions And Answers

Electric Cables MCQs. Multiple Choice Questions and Answers related to Electric Cables and their insulation, mechanism of flow of current through cables and other related things in Electrical Engineering.

 

Electric Cables MCQs

 

PVC stands for ?

A. polyvinyl chloride
B. post varnish conductor
C. pressed and varnished cloth
D. positive voltage conductor

View Answer

A. polyvinyl chloride

 

In case of three core flexible cable the colour of the neutral is ?

A. blue
B. black
C. brown
D. none of the above

View Answer

A. blue

 

Which of the following insulation is used in cables ?

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

View Answer

D. Any of the above

 

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

A. insulation layer
B. sheath
C. armour
D. conductor surface

View Answer

D. conductor surface

 

Dielectric strength of rubber is around ?

A. 5 kV/mm
B. 15 kV/mm
C. 30 kV/mm
D. 200 kV/mm

View Answer

C. 30 kV/mm

 

The insulating material for a cable should have ?

A. low cost
B. high dielectric strength
C. high mechanical strength
D. all of the above

View Answer

D. all of the above

 

Which of the following protects a cable against mechanical injury ?

A. Bedding
B. Sheath
C. Armouring
D. None of the above

View Answer

C. Armouring

 

High tension cables are generally used up to ?

A. 11 kV
B. 33 kV
C. 66 kV
D. 132 kV

View Answer

A. 11 kV

 

Electric Cables MCQs

 

Low tension cables are generally used up to ?

A. 200 V
B. 500 V
C. 700 V
D. 1000 V

View Answer

D. 1000 V

 

The bedding on a cable consists of ?

A. hessian cloth
B. jute
C. any of the above
D. none of the above

View Answer

C. any of the above

 

Cables are used for 132 kV lines ?

A. High tension
B. Super tension
C. Extra high tension
D. Extra super voltage

View Answer

D. Extra super voltage

 

The minimum dielectric stress in a cable is at ?

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

View Answer

D. lead sheath

 

The insulating material for cables should ?

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

View Answer

D. have all above properties

 

The material for armouring on cable is usually ?

A. steel tape
B. galvanised steel wire
C. any of the above
D. none of the above

View Answer

C. any of the above

 

The electrostatic stress in underground cables is ?

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

View Answer

C. maximum at the conductor and minimum at the sheath

 

A cable carrying alternating current has ?

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

View Answer

B. hysteresis and leakage losses only

 

Electric Cables MCQs

 

The insulating material for a cable should have ?

A. low permittivity
B. high resistivity
C. high dielectric strength
D. all of the above

View Answer

D. all of the above

 

Copper as conductor for cables is used as ?

A. annealed
B. hardened and tempered
C. hard drawn
D. alloy with chromium

View Answer

A. annealed

 

The breakdown voltage of a cable depends on ?

A. presence of moisture
B. working temperature
C. time of application of the voltage
D. all of the above

View Answer

D. all of the above

 

The thickness of metallic shielding on cables is usually ?

A. 0.04 mm
B. 0.2 to 0.4 mm
E. 3 to 5 mm
D. 40 to 60 mm

View Answer

A. 0.04 mm

 

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

View Answer

A. avoid excessive sheath losses

 

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

View Answer

C. voltage

 

Empire tape is ?

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

View Answer

A. varnished cambric

 

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. the capacitance of insulated conductors
D. all above parameters

View Answer

C. the capacitance of insulated conductors

 

Electric Cables MCQs

 

The surge resistance of cable is ?

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

View Answer

C. 50 ohms

 

Conduit pipes are normally used to protect _______ cables ?

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

View Answer

A. unsheathed cables

 

In cables the charging current ?

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

View Answer

B. leads the voltage by 90°

 

The disadvantage with paper as insulating material is ?

A. it is hygroscopic
B. it has high capacitance
C. it is an organic material
D. none of the above

View Answer

A. it is hygroscopic

 

Cables for 220 kV lines are invariably ?

A. mica insulated
B. paper insulated
C. compressed oil or compressed gas insulated
D. rubber insulated

View Answer

C. compressed oil or compressed gas insulated

 

The advantage of cables over overhead transmission lines is ?

A. easy maintenance
B. low cost
C. can be used in congested areas
D. can be used in high voltage circuits

View Answer

C. can be used in congested areas

 

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

View Answer

A. the increase in length of the insulation

 

In a cable the voltage stress is maximum at ?

A. sheath
B. insulator
C. surface of the conductor
D. core of the conductor

View Answer

D. core of the conductor

 

Electric Cables MCQs

 

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 minimize the effect of shocks and vibrations due to gassing vehicles, etc
D. for all of the above reasons

View Answer

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

 

In a cable immediately above metallic sheath ______ is provided ?

A. earthing connection
B. bedding
C. armouring
D. none of the above

View Answer

B. bedding

 

Cables, generally used beyond 66 kV are ?

A. oil filled
B. S.L. type
C. belted
D. armoured

View Answer

A. oil filled

 

The current carrying capacity of cables in D.C. is more than that in A.C. mainly due to ?

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

View Answer

C. smaller dielectric loss

 

The intersheaths in the cables are used to ?

A. minimize the stress
B. avoid the requirement of good insulation
C. provide proper stress distribution
D. none of the above

View Answer

C. provide proper stress distribution

 

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

A. inter-sheaths
B. insulating materials with different dielectric constants
C. both A and B
D. none of the above

View Answer

C. both A and B

 

In capacitance grading of cables we use a _______ dielectric ?

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

View Answer

A. composite

 

The relative permittivity of rubber is ?

A. between 2 and 3
B. between 5 and 6
C. between 8 and 10
D. between 12 and 14

View Answer

A. between 2 and 3

 

Electric Cables MCQs

 

In the cables, sheaths are used to ?

A. prevent the moisture from entering the cable
B. provide enough strength
C. provide proper insulation
D. none of the above

View Answer

A. prevent the moisture from entering the cable

 

If the length of a cable is doubled, its capacitance ?

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

View Answer

C. becomes double

 

Pressure cables are generally not used beyond ?

A. 11 kV
B. 33 kV
C. 66 kV
D. 132 kV

View Answer

C. 66 kV

 

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 ?

A. one half
B. double
C. four times
D. none of the above

View Answer

A. one half

 

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

View Answer

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

 

The metallic sheath may be made of lead or lead alloy or of aluminium ?

A. Yes
B. No

View Answer

B. No

 

It is difficult to maintain oil filled cables ?

A. Yes
B. No

View Answer

A. Yes

 

In congested areas where excavation is expensive and inconvenient ‘draw in system’ of laying of underground cables is often adopted ?

A. Yes
B. No

View Answer

A. Yes

 

Electric Cables MCQs

 

Polyethylene has very poor dielectric and ageing properties ?

A. Yes
B. No

View Answer

B. No

 

If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be ?

A. 5 kV/mm
B. 10 kV/mm
A. 15 kV/mm
D. 30 kV/mm

View Answer

B. 10 kV/mm

 

Natural rubber is obtained from milky sap of tropical trees ?

A. Yes
B. No

View Answer

A. Yes

 

In capacitance grading a homogeneous dielectric is used ?

A. Yes
B. No

View Answer

B. No

 

Rubber is most commonly used insulation in cables ?

A. Yes
B. No

View Answer

A. Yes

 

If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be ?

A. 2 cm
B. 10 cm
C. 50 cm
D. 400 cm

View Answer

C. 50 cm

 

Capacitance grading of cable implies ?

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

View Answer

A. use of dielectrics of different permeabilities

 

The advantage of oil filled cables is ?

A. more perfect impregnation
B. smaller overall size
C. no ionisation, oxidation and formation of voids
D. all of the above

View Answer

D. all of the above

 

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

A. Polyvinyle chloride
B. Vulcanised rubber
C. Impregnated paper
D. Compressed SFe gas

View Answer

D. Compressed SFe gas

 

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