McqMate
| 101. |
A series generator can self-excite |
| A. | only if the load current is zero |
| B. | only if the load current is not zero |
| C. | irrespective of the value of load current |
| D. | none of the above |
| Answer» B. only if the load current is not zero | |
| 102. |
A shunt generator can self-excite |
| A. | only if the resistance of the field circuit is less than critical value |
| B. | only if the resistance of the field circuit is greater than critical value |
| C. | irrespective of the value of the resis-tance in the field circuit |
| Answer» A. only if the resistance of the field circuit is less than critical value | |
| 103. |
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be |
| A. | 150 V |
| B. | less than 150 V |
| C. | greater than 150 V |
| D. | none of the above |
| Answer» C. greater than 150 V | |
| 104. |
The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage |
| A. | will be less than 250 V |
| B. | will always be 250 V |
| C. | may be greater or less than 250 V |
| D. | none of the above |
| Answer» C. may be greater or less than 250 V | |
| 105. |
Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be |
| A. | 270 V |
| B. | 267.5 V |
| C. | 265 V |
| D. | 257.4 V |
| Answer» B. 267.5 V | |
| 106. |
The essential condition for parallel operation of two D.C. generators is that they have |
| A. | same kW rating |
| B. | the same operation r.p.m. |
| C. | the same drooping voltage charac-teristics |
| D. | same percentage regulation |
| Answer» C. the same drooping voltage charac-teristics | |
| 107. |
When two D.C. generators are running in parallel an equilizer bar is used |
| A. | to increase the series flux |
| B. | to increase the generated e.m.f. |
| C. | to reduce the combined effect of ar-mature reaction of both the machines |
| D. | so that the two identical machines will pass approximately equal currents to the load |
| Answer» D. so that the two identical machines will pass approximately equal currents to the load | |
| 108. |
With a D.C. generator which of the following regulation is preferred ? |
| A. | 100% regulation |
| B. | infinite regulation |
| C. | 50% regulation |
| D. | 1% regulation |
| Answer» D. 1% regulation | |
| 109. |
Which generator would you prefer for feeding long D.C. transmission lines ? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Over compound generator |
| D. | Flat compound generator |
| Answer» C. Over compound generator | |
| 110. |
In a D.C. generator the critical resistance can be increased by |
| A. | increasing its field resistance |
| B. | decreasing its field resistance |
| C. | increasing its speed |
| D. | decreasing its speed |
| Answer» C. increasing its speed | |
| 111. |
The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» B. 4 | |
| 112. |
For both lap and wave windings, there are as many commutator bars as the number of |
| A. | slots |
| B. | armature conductors |
| C. | winding elements |
| D. | poles |
| Answer» C. winding elements | |
| 113. |
The series field of a short-shunt D.C. generator is excited by |
| A. | external current |
| B. | armature current |
| C. | shunt current |
| D. | load current |
| Answer» D. load current | |
| 114. |
As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately |
| A. | 40 percent |
| B. | 25 percent |
| C. | 10 percent |
| D. | 5 percent |
| Answer» D. 5 percent | |
| 115. |
Shunt generators are most suited for stable parallel operation because of their |
| A. | rising voltage characteristics |
| B. | identical voltage characteristics |
| C. | drooping voltage characteristics |
| D. | linear voltage characteristics |
| Answer» C. drooping voltage characteristics | |
| 116. |
The main factor which leads to unstable parallel operation of flat and over compounded generators is |
| A. | their rising voltage characteristics |
| B. | unequal number of turns in their series field windings |
| C. | unequal speed regulation of their primemovers |
| D. | unequal series field resistances |
| Answer» A. their rising voltage characteristics | |
| 117. |
If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to |
| A. | reverse the field connections |
| B. | increase the field resistance |
| C. | increase the speed of primemover |
| D. | check armature insulation resis¬tance |
| Answer» A. reverse the field connections | |
| 118. |
The insulating material for a cable should have |
| A. | low cost |
| B. | high dielectric strength |
| C. | high mechanical strength |
| D. | all of the above |
| Answer» D. all of the above | |
| 119. |
Which of the following protects a cable against mechanical injury ? |
| A. | Bedding |
| B. | Sheath |
| C. | Armouring |
| D. | None of the above |
| Answer» C. Armouring | |
| 120. |
Which of the following insulation is used in cables ? |
| A. | Varnished cambric |
| B. | Rubber |
| C. | Paper |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 121. |
Empire tape is |
| A. | varnished cambric |
| B. | vulcanised rubber |
| C. | impregnated paper |
| D. | none of the above |
| Answer» A. varnished cambric | |
| 122. |
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 |
| Answer» C. voltage | |
| 123. |
The bedding on a cable consists of |
| A. | hessian cloth |
| B. | jute |
| C. | any of the above |
| D. | none of the above |
| Answer» C. any of the above | |
| 124. |
The insulating material for cables should |
| A. | be acid proof |
| B. | be non-inflammable |
| C. | be non-hygroscopic |
| D. | have all above properties |
| Answer» D. have all above properties | |
| 125. |
In a cable immediately above metallic sheath _____ is provided. |
| A. | earthing connection |
| B. | bedding |
| C. | armouring |
| D. | none of the above |
| Answer» B. bedding | |
| 126. |
The current carrying capacity of cables in D.C. is more thanthat 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 |
| Answer» C. smaller dielectric loss | |
| 127. |
In case of three core flexible cable the colour of the neutral is |
| A. | blue |
| B. | black |
| C. | brown |
| D. | none of the above |
| Answer» A. blue | |
| 128. |
cables are used for 132 kV lines. |
| A. | High tension |
| B. | Super tension |
| C. | Extra high tension |
| D. | Extra super voltage |
| Answer» D. Extra super voltage | |
| 129. |
Conduit pipes are normally used to protect _____ cables. |
| A. | unsheathed cables |
| B. | armoured |
| C. | PVC sheathed cables |
| D. | all of the above |
| Answer» A. unsheathed cables | |
| 130. |
The minimum dielectric stress in a cable is at |
| A. | armour |
| B. | bedding |
| C. | conductor surface |
| D. | lead sheath |
| Answer» D. lead sheath | |
| 131. |
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 |
| Answer» A. avoid excessive sheath losses | |
| 132. |
Dielectric strength of rubber is around |
| A. | 5 kV/mm |
| B. | 15 kV/mm |
| C. | 30 kV/mm |
| D. | 200 kV/mm |
| Answer» C. 30 kV/mm | |
| 133. |
Low tension cables are generally used upto |
| A. | 200 V |
| B. | 500 V |
| C. | 700 V |
| D. | 1000 V |
| Answer» D. 1000 V | |
| 134. |
In a cable, the maximum stress under operating conditions is at |
| A. | insulation layer |
| B. | sheath |
| C. | armour |
| D. | conductor surface |
| Answer» D. conductor surface | |
| 135. |
High tension cables are generally used upto |
| A. | 11kV |
| B. | 33kV |
| C. | 66 kV |
| D. | 132 kV |
| Answer» A. 11kV | |
| 136. |
The surge resistance of cable is |
| A. | 5 ohms |
| B. | 20 ohms |
| C. | 50 ohms |
| D. | 100 ohms |
| Answer» C. 50 ohms | |
| 137. |
PVC stands for |
| A. | polyvinyl chloride |
| B. | post varnish conductor |
| C. | pressed and varnished cloth |
| D. | positive voltage conductor |
| Answer» A. polyvinyl chloride | |
| 138. |
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 capacitances of insulated conductors |
| D. | all above parameters |
| Answer» C. the capacitances of insulated conductors | |
| 139. |
In capacitance grading of cables we use a ______ dielectric. |
| A. | composite |
| B. | porous |
| C. | homogeneous |
| D. | hygroscopic |
| Answer» A. composite | |
| 140. |
Pressure cables are generally not used beyond |
| A. | 11 kV |
| B. | 33 kV |
| C. | 66 kV |
| D. | 132 kV |
| Answer» C. 66 kV | |
| 141. |
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 |
| Answer» C. any of the above | |
| 142. |
Cables, generally used beyond 66 kV are |
| A. | oil filled |
| B. | S.L. type |
| C. | belted |
| D. | armoured |
| Answer» A. oil filled | |
| 143. |
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 |
| Answer» A. between 2 and 3 | |
| 144. |
Solid type cables are considered unreliable beyond 66 kV because |
| A. | insulation may melt due to higher temperature |
| B. | skin effect dominates on the conduc¬tor |
| C. | of corona loss between conductor and sheath material |
| D. | there is a danger of breakdown of insulation due to the presence of voids |
| Answer» D. there is a danger of breakdown of insulation due to the presence of voids | |
| 145. |
If the length of a cable is doubled, its capacitance |
| A. | becomes one-fourth |
| B. | becomes one-half |
| C. | becomes double |
| D. | remains unchanged |
| Answer» C. becomes double | |
| 146. |
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° |
| Answer» B. leads the voltage by 90° | |
| 147. |
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 |
| Answer» A. one half | |
| 148. |
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 |
| C. | 15 kV/mm |
| D. | 30 kV/mm |
| Answer» B. 10 kV/mm | |
| 149. |
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 |
| Answer» A. prevent the moisture from entering the cable | |
| 150. |
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 |
| Answer» C. provide proper stress distribution | |
| 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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