Electrical Cables — Part 1 MCQs with Explanations

The correct answer is (C) Becomes double Here's why: Capacitance (C) of a cable is determined by the following factors: * The dielectric constant of the insulation material. * The area of the conductors. * The distance between the conductors (thickness of insulation). * The length of the cable. Think of a cable like a parallel plate capacitor. The formula for capacitance is roughly: C = (ε * A) / d Where: ε is the permittivity (related to the dielectric constant). A is the area of overlap of the conductors. d is the distance between the conductors. When the length of the cable is doubled, it's like increasing the area of overlap (A) between the conductors. Imagine connecting two identical capacitors in parallel. The total capacitance doubles. Therefore, if you double the length of the cable, you effectively double the capacitance .

In a cable, the voltage stress refers to the electrical stress experienced by the materials within the cable when it is subjected to an electric field. The voltage stress is maximum at the surface of the conductor. This is due to the phenomenon known as the skin effect . The skin effect causes the distribution of current within a conductor to be concentrated near the surface when the frequency of the electrical signal is high. As a result, the majority of the current flows through a thin layer near the surface of the conductor, leading to a higher voltage stress at the surface compared to the core. Therefore, Option C correctly identifies that the voltage stress is maximum at the surface of the conductor in a cable.

Any of the above is the correct answer to “The bedding on a cable consists of”. This question is standard in competitive examination syllabi for Electrical Cables.

All of the above is the correct answer to “The insulating material for a cable should have”. This question is standard in competitive examination syllabi for Electrical Cables.

To minimize the effect of shocks and vibrations due to gassing vehicles, etc. is the correct answer to “Underground cables are laid at sufficient depth”. This question is standard in competitive examination syllabi for Electrical Cables.

No is the correct answer to “In capacitance grading a homogeneous dielectric is used.”. This question is standard in competitive examination syllabi for Electrical Cables.

30 kV/mm is the correct answer to “Dielectric strength of rubber is around”. This question is standard in competitive examination syllabi for Electrical Cables.

Any of the above is the correct answer to “The material for armouring on cable is usually”. This question is standard in competitive examination syllabi for Electrical Cables.

Prevent the moisture from entering the cable is the correct answer to “In the cables, sheaths are used to”. This question is standard in competitive examination syllabi for Electrical Cables.

Bedding is the correct answer to “In a cable immediately above metallic sheath ________ is provided.”. This question is standard in competitive examination syllabi for Electrical Cables.

Composite is the correct answer to “In capacitance grading of cables we use a _________ dielectric.”. This question is standard in competitive examination syllabi for Electrical Cables.

Have all above properties is the correct answer to “The insulating material for cables should”. This question is standard in competitive examination syllabi for Electrical Cables.

66 kV is the correct answer to “Pressure cables are generally not used beyond”. This question is standard in competitive examination syllabi for Electrical Cables.

There is a danger of breakdown of insulation due to the presence of voids is the correct answer to “Solid type cables are considered unreliable beyond 66 kV because”. This question is standard in competitive examination syllabi for Electrical Cables.

The increase in length of the insulation is the correct answer to “The insulation of the cable decreases with”. This question is standard in competitive examination syllabi for Electrical Cables.

Voltage is the correct answer to “The thickness of the layer of insulation on the conductor, in cables, depends upon”. This question is standard in competitive examination syllabi for Electrical Cables.

No is the correct answer to “Polyethylene has very poor dielectric and ageing properties.”. This question is standard in competitive examination syllabi for Electrical Cables.

Provide proper stress distribution is the correct answer to “The inters heaths in the cables are used to”. This question is standard in competitive examination syllabi for Electrical Cables.

Unsheathed cables is the correct answer to “Conduit pipes are normally used to protect ________ cables.”. This question is standard in competitive examination syllabi for Electrical Cables.

Extra super voltage is the correct answer to “_________ cables are used for 132 kV lines.”. This question is standard in competitive examination syllabi for Electrical Cables.

Varnished cambric is the correct answer to “Empire tape is”. This question is standard in competitive examination syllabi for Electrical Cables.

50 cm is the correct answer to “If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be”. This question is standard in competitive examination syllabi for Electrical Cables.

Hysteresis and leakage losses only is the correct answer to “A cable carrying alternating current has”. This question is standard in competitive examination syllabi for Electrical Cables.

Yes is the correct answer to “In congested areas where excavation is expensive and inconvenient 'draw in system' of laying of underground cables is often adopted.”. This question is standard in competitive examination syllabi for Electrical Cables.

Lead sheath is the correct answer to “The minimum dielectric stress in a cable is at”. This question is standard in competitive examination syllabi for Electrical Cables.

All of the above is the correct answer to “The breakdown voltage of a cable depends on”. This question is standard in competitive examination syllabi for Electrical Cables.

11 kV is the correct answer to “High tension cables are generally used up to”. This question is standard in competitive examination syllabi for Electrical Cables.

1000 V is the correct answer to “Low tension cables are generally used up to”. This question is standard in competitive examination syllabi for Electrical Cables.

One half is the correct answer to “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”. This question is standard in competitive examination syllabi for Electrical Cables.

Both (A) and (B) is the correct answer to “The breakdown of insulation of the cable can be avoided economically by the use of”. This question is standard in competitive examination syllabi for Electrical Cables.

Conductor surface is the correct answer to “In a cable, the maximum stress under operating conditions is at”. This question is standard in competitive examination syllabi for Electrical Cables.

Use of dielectrics of different permeabilities is the correct answer to “Capacitance grading of cable implies”. This question is standard in competitive examination syllabi for Electrical Cables.

10 kV/mm is the correct answer to “If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be”. This question is standard in competitive examination syllabi for Electrical Cables.

Compressed oil or compressed gas insulated is the correct answer to “Cables for 220 kV lines are invariably”. This question is standard in competitive examination syllabi for Electrical Cables.

No is the correct answer to “The metallic sheath may be made of lead or lead alloy or of aluminum.”. This question is standard in competitive examination syllabi for Electrical Cables.

All of the above is the correct answer to “The insulating material should have”. This question is standard in competitive examination syllabi for Electrical Cables.

Smaller dielectric loss is the correct answer to “The current carrying capacity of cables in D.C. is more than that in A.C. mainly due to”. This question is standard in competitive examination syllabi for Electrical Cables.

Any of the above is the correct answer to “Which of the following insulation is used in cables”. This question is standard in competitive examination syllabi for Electrical Cables.

Yes is the correct answer to “It is difficult to maintain oil filled cables.”. This question is standard in competitive examination syllabi for Electrical Cables.

Compressed SFe gas is the correct answer to “Is a cable is to be designed for use on 1000 kV, which insulation would you prefer”. This question is standard in competitive examination syllabi for Electrical Cables.