# Material Science 7

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Material Science 7

Part 1: List for questions and answers of Material Science

Q1. The thickness of insulation provided on the conductor in the cable depends on which among the following factor?

a) Operating voltage

b) Current to be carried

c) Power factor

d) Both (a) and (b)

Q2. The insulation resistance of a cable of length 10 km is 1M ohm . For a length of 100 km of the same cable, what will be the insulation resistance?

a)1 M ohm

b)10 M ohm

c)0.1 M ohm

d)0.01 M ohm

Q3. What is the main drawback of using paper as the insulating material?

a) Is hygroscopic

b) Has poor dielectric strength

c) Has a very low insulation resistivity

d) Has high capacitance

Q4. What is the limit of the conductor cross section when paper insulation is used?

a) 50 mm^2

b) 250 mm^2

c) 600 mm^2

d) 1200 mm^2

Q5. What is the dielectric strength of impregnated paper?

a) 30 kV/mm

b) 20 kV/mm

c) 15 kV/mm

d) 5 kV/mm

Q6. What is empire tape?

a) Impregnated paper

b) Vulcanised rubber

c) Enamel insulation

d) Varnished cambric

Q7. What is the percentage of added materials like sulphur, zinc lead etc in vulcanised

rubber?

a) 5-10%

b) 3-5%

c) 4-8%

d) 10-12%

Q8. How many cores are used in a cable for the transmission of voltages upto 66 kV?

a) Single core

b) Two core

c) Three core

d) All of the above

Q9. Why is the single core cables not provided with armouring?

a) Avoids excessive loss in the armour

b) Make the cable more flexible

c) Make the cable non hygroscopic

d) None of the above

Q10. QWhich among the following cables are generally suited for the voltages upto 11 kV?

a) Belted cables

b) Screened cables

c) Pressure cables

d) None of these

Q11. Which material is suitable for the manufacture of armour in a single core cable?

a) Magnetic material

b) Non magnetic and non conducting material

c) Non magnetic and conducting material

d) Magnetic and non conducting material

Q12. Why the belted type cable constructions are not suitable for voltages exceeding 22 kV?

a) Development of both radial and tangential stress

homogeneity of dielectric in belted construction

c) Local heating caused by power loss at the centre filling

d) All of the above

Q13. The cable best suited for the transmission of voltages from 33 kV to 66 kV is_______

a) Belted cables

b) Screened cables

c) Pressure cables

d) None of these

Q14. What is/ are the advantages of using H-type cables?

a) The metallic screens assist in complete impregnation of the cable with the compound

b) The metallic screens increase the heat dissipating power of the cable

c) The lead sheaths in H type are thicker then S.L type cables

d) All of these

Q15. What is the advantage(s) of screened type over the belted cables?

a) Reduced possibility of core to core faults

b) Increased current carrying capacity

c) No possibility of formation of voids within the dielectric

d) All of the above

Q16. What is the gas pressure of SF6 for a compressed gas insulated cable?

a) 10-20mm Hg

b) 80-100mm Hg

c) 3-5 kg/cm^2

d) 40-50kg/cm^2

Q17. Why are the ternary lead cables used near the railway tracks?

a) Because they have high tensile strength

b) Have a low coefficient of thermal expansion

c) Have low specific gravity

d) Can withstand shocks and vibrations

Q18. Why solid type of conductors is not preferred for the voltages exceeding 66 kV?

a) A danger of breakdown of insulation

b) Skin effect dominates the conductor

c) There is corona loss between conductor and sheath material

d) Insulation melts due to overheating

Q19. The charging current drawn by the cable _____

a) Lags behind the voltage by 90 degree

b) Leads the voltage by 90 degree

c) Are in phase with each other

d) Leads the voltage by 60 degree

Q20. What is the source of heat generation in cables?

a) Copper loss in conductor

b) Dielectric losses in cable insulation

c) Losses in metallic sheathings and armouring

d) All of these

Part 1: List for questions and answers of Material Science