McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 151. |
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 |
| Answer» C. maximum at the conductor and minimum at the sheath | |
| 152. |
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 |
| Answer» C. both (a) and (b) | |
| 153. |
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 |
| Answer» A. the increase in length of the insulation | |
| 154. |
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 |
| Answer» B. hysteresis and leakage losses only | |
| 155. |
In a cable the voltage stress is maximum at |
| A. | sheath |
| B. | insulator |
| C. | surface of the conductor |
| D. | core of the conductor |
| Answer» D. core of the conductor | |
| 156. |
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 |
| Answer» A. use of dielectrics of different permeabilities | |
| 157. |
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 |
| Answer» C. to minimise the effect of shocks and vibrations due to gassing vehicles, etc. | |
| 158. |
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 |
| Answer» C. can be used in congested areas | |
| 159. |
The thickness of metallic shielding on cables is usually |
| A. | 0.04 mm |
| B. | 0.2 to 0.4 mm |
| C. | 3 to 5 mm |
| D. | 40 to 60 mm |
| Answer» A. 0.04 mm | |
| 160. |
Cables for 220 kV lines are invariably |
| A. | mica insulated |
| B. | paper insulated |
| C. | compressed oil or compressed gas insulated |
| D. | rubber insulated |
| Answer» C. compressed oil or compressed gas insulated | |
| 161. |
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 |
| Answer» D. Compressed SFe gas | |
| 162. |
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 |
| Answer» C. 50 cm | |
| 163. |
Copper as conductor for cables is used as |
| A. | annealed |
| B. | hardened and tempered |
| C. | hard drawn |
| D. | alloy with chromium |
| Answer» A. annealed | |
| 164. |
The insulating material should have |
| A. | low permittivity |
| B. | high resistivity |
| C. | high dielectric strength |
| D. | all of the above |
| Answer» D. all of the above | |
| 165. |
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 |
| Answer» D. all of the above | |
| 166. |
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 |
| Answer» A. it is hygroscopic | |
| 167. |
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 |
| Answer» D. all of the above | |
| 168. |
In capacitance grading a homogeneous dielectric is used. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» B. No | |
| 169. |
In congested areas where excavation is expensive and inconvenient 'draw in system' of laying of underground cables is often adopted. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» A. Yes | |
| 170. |
Natural rubber is obtained from milky sap of tropical trees. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» A. Yes | |
| 171. |
Rubber is most commonly used insulation in cables. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» A. Yes | |
| 172. |
Polyethylene has very poor dielectric and ageing properties. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» B. No | |
| 173. |
The metallic sheath may be made of lead or lead alloy or of aluminium. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» B. No | |
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