That's a great request! Here are 25 Multiple Choice Questions (MCQs) on the topic of electrical cables, covering construction, classification, and properties.
🔌 Cable Multiple Choice Questions (MCQ)
Part 1: Cable Construction and Components
1. The outermost protective covering of an underground cable is called the:
A. Insulation
B. Sheath
C. Bedding
D. Serving
Correct Answer: D. Serving
2. What is the main purpose of the metallic sheath in an underground cable?
A. To provide mechanical strength.
B. To protect the cable against moisture, gases, and other liquids.
C. To prevent the flow of charging current.
D. To provide a path for the return current.
Correct Answer: B. To protect the cable against moisture, gases, and other liquids.
3. In a cable, the layer of material applied immediately above the metallic sheath is called:
A. Bedding
B. Armouring
C. Serving
D. Insulation
Correct Answer: A. Bedding
4. The armouring in an electric cable is provided to:
A. Increase the current-carrying capacity.
B. Protect the cable from mechanical injury.
C. Facilitate stress grading.
D. Reduce the overall cost.
Correct Answer: B. Protect the cable from mechanical injury.
5. The material typically used for the conductor in electrical power cables is:
A. Steel
B. Copper or Aluminium
C. Lead
D. Rubber
Correct Answer: B. Copper or Aluminium
6. Which of the following is NOT a desirable property for an insulating material in a cable?
A. High Dielectric Strength
B. High Resistivity
C. High Permittivity (Dielectric Constant)
D. Non-hygroscopic (Water-resistant)
Correct Answer: C. High Permittivity (Dielectric Constant)
7. PVC stands for:
A. Positive Voltage Conductor
B. Pressed and Varnished Cloth
C. Polyvinyl Chloride
D. Power Voltage Cable
Correct Answer: C. Polyvinyl Chloride
Part 2: Cable Classification and Voltage Levels
8. Low Tension (L.T.) cables are generally used for operating voltages up to:
A. 11 kV
B. 3.3 kV
C. 650 V
D. 1 kV
Correct Answer: D. 1 kV
9. High Tension (H.T.) cables are typically designed to operate up to:
A. 1 kV
B. 11 kV
C. 33 kV
D. 66 kV
Correct Answer: B. 11 kV
10. Cables that are generally used beyond 66 kV are often of which type?
A. Belted cables
B. Screened cables (H-type)
C. Pressure cables (Oil-filled or Gas-filled)
D. Armoured cables
Correct Answer: C. Pressure cables (Oil-filled or Gas-filled)
11. Which type of cable is structurally simple and is mainly used for voltages up to 11 kV?
A. Screened Cable
B. Belted Cable
C. Pressure Cable
D. Coaxial Cable
Correct Answer: B. Belted Cable
12. Cross-Linked Polyethylene (XLPE) is an example of what type of insulating material?
A. Thermoplastic
B. Thermosetting
C. Halogen-free thermoplastic
D. Vulcanised rubber
Correct Answer: B. Thermosetting
13. In a 3.5 core cable, the neutral conductor has a cross-sectional area that is typically:
A. Half the area of the phase conductors.
B. Equal to the area of the phase conductors.
C. Double the area of the phase conductors.
D. Negligible.
Correct Answer: A. Half the area of the phase conductors.
Part 3: Electrical Characteristics and Stress
14. In cables, the thickness of the insulation layer depends mainly on the:
A. Current to be carried
B. Power factor
C. Operating voltage
D. Length of the cable
Correct Answer: C. Operating voltage
15. The electrostatic stress in an underground cable is maximum at the:
A. Lead sheath
B. Bedding layer
C. Armouring layer
D. Conductor surface
Correct Answer: D. Conductor surface
16. The concept of using dielectrics of different permittivities (dielectric constants) to equalize the stress distribution in a cable is known as:
A. Inter-sheath grading
B. Capacitance grading
C. Voltage balancing
D. Homogeneous insulation
Correct Answer: B. Capacitance grading
17. What is the effect on the capacitance of a cable if its length is doubled?
A. It becomes one-fourth.
B. It remains unchanged.
C. It becomes double.
D. It becomes one-half.
Correct Answer: C. It becomes double.
($C \propto L$, where $C$ is capacitance and $L$ is length)
18. The charging current in a cable:
A. Lags the voltage by $90^\circ$.
B. Leads the voltage by $90^\circ$.
C. Is in phase with the voltage.
D. Leads the voltage by $60^\circ$.
Correct Answer: B. Leads the voltage by $90^\circ$.
19. For a single-core cable, the ratio of the sheath diameter to the core diameter ($D/d$) for minimum stress at the conductor surface is approximately:
A. 1.718
B. 2.718 (i.e., $e$)
C. 3.14
D. 4.00
Correct Answer: B. 2.718 (i.e., $e$)
Part 4: Specific Cable Types and Terminology
20. What is the term for the maximum current a conductor can carry continuously under the conditions of use without exceeding its temperature rating?
A. Voltage Rating
B. Short-circuit Capacity
C. Ampacity
D. Breakdown Voltage
Correct Answer: C. Ampacity
21. A cable that uses strands of glass or plastic fiber to transmit data as light signals is a:
A. Coaxial cable
B. Twisted-pair cable
C. Fibre Optic cable
D. Armoured cable
Correct Answer: C. Fibre Optic cable
22. Which of the following cable types is typically used for telecommunication and has a central conductor surrounded by a layer of insulation, then a shield, and finally an outer sheath?
A. Twisted-pair
B. Coaxial
C. Fibre Optic
D. Busbar
Correct Answer: B. Coaxial
23. The main advantage of stranded conductors over solid conductors is:
A. Lower cost
B. Greater flexibility
C. Higher maximum voltage rating
D. Simpler termination
Correct Answer: B. Greater flexibility
24. The minimum dielectric stress in a single-core cable under operating conditions occurs at the:
A. Sheath surface
B. Conductor surface
C. Middle of the insulation
D. Bedding layer
Correct Answer: A. Sheath surface
25. A commonly used armoured cable for high-tension overhead transmission lines is:
A. AAC (All Aluminium Conductor)
B. AAAC (All Aluminium Alloy Conductor)
C. ACSR (Aluminium Conductor Steel Reinforced)
D. PVC (Polyvinyl Chloride)
Correct Answer: C. ACSR (Aluminium Conductor Steel Reinforced)
Would you like to review the solutions or have a diagram of a typical underground cable's construction?
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