MCQOPTIONS
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MCQOPTIONS
This section includes 209 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
The path of the magnetic flux in transformer should have$? |
| A. | high reluctance |
| B. | low reactance |
| C. | high resistance |
| D. | low resistance |
| Answer» C. high resistance | |
| 152. |
In a certain transformer, the input power to the primary is 120 W. If 8.5 W are lost to the winding resistance, what is the output power to the load, neglecting any other issues?$? |
| A. | 0 W |
| B. | 14.1 W |
| C. | 111.5 W |
| D. | 1,020 W |
| Answer» D. 1,020 W | |
| 153. |
An ideal transformer is one which has$? |
| A. | no losses and magnetic leakage |
| B. | interleaved primary and secondary windings |
| C. | a common core for its primary and secondary windings |
| D. | core of stainless steel and winding of pure copper metal |
| Answer» B. interleaved primary and secondary windings | |
| 154. |
Primary winding of a transformer$? |
| A. | is always a low voltage winding |
| B. | is always a high voltage winding |
| C. | could either be a low voltage or high voltage winding |
| D. | none of the above |
| Answer» D. none of the above | |
| 155. |
Efficiency of a power transformer is of the order of$? |
| A. | 100 per cent |
| B. | 98 per cent |
| C. | 50 per cent |
| D. | 25 per cent |
| Answer» C. 50 per cent | |
| 156. |
A common method of cooling a power transformer is$? |
| A. | natural air cooling |
| B. | air blast cooling |
| C. | oil cooling |
| D. | any of the above |
| Answer» D. any of the above | |
| 157. |
The secondary of a current transformer is always short-circuited under operating conditions because it$? |
| A. | avoids core saturation and high voltage induction |
| B. | is safe to human beings |
| C. | protects the primary circuit |
| D. | none of the above |
| Answer» B. is safe to human beings | |
| 158. |
A transformer has a 1:6 turns ratio and a secondary coil load resistance of 470 Ω. The load resistance as seen by the source is? |
| A. | 1.3 Ω |
| B. | 7.8 Ω |
| C. | 78 Ω |
| D. | 13 Ω |
| Answer» E. | |
| 159. |
While conducting short-circuit test on a transformer the following side is short circuited? |
| A. | High voltage side |
| B. | Low voltage side |
| C. | Primary side |
| D. | Secondary side |
| Answer» C. Primary side | |
| 160. |
Two transformers operating in parallel will share the load depending upon their? |
| A. | leakage reactance |
| B. | per unit impedance |
| C. | efficiencies |
| D. | ratings |
| Answer» C. efficiencies | |
| 161. |
A transformer core is laminated to? |
| A. | reduce hysteresis loss |
| B. | reduce eddy current losses |
| C. | reduce copper losses |
| D. | reduce all above losses |
| Answer» C. reduce copper losses | |
| 162. |
No-load on a transformer is carried out to determine? |
| A. | copper loss |
| B. | magnetising current |
| C. | magnetising current and loss |
| D. | efficiency of the transformer |
| Answer» D. efficiency of the transformer | |
| 163. |
An ideal transformer is one which has? |
| A. | no losses and magnetic leakage |
| B. | interleaved primary and secondary windings |
| C. | a common core for its primary and secondary windings |
| D. | core of stainless steel and winding of pure copper metal |
| Answer» B. interleaved primary and secondary windings | |
| 164. |
Primary winding of a transformer? |
| A. | is always a low voltage winding |
| B. | is always a high voltage winding |
| C. | could either be a low voltage or high voltage winding |
| D. | none of the above |
| Answer» D. none of the above | |
| 165. |
The path of the magnetic flux in transformer should have? |
| A. | high reluctance |
| B. | low reactance |
| C. | high resistance |
| D. | low resistance |
| Answer» C. high resistance | |
| 166. |
In a certain transformer, the input power to the primary is 120 W. If 8.5 W are lost to the winding resistance, what is the output power to the load, neglecting any other issues?? |
| A. | 0 W |
| B. | 14.1 W |
| C. | 111.5 W |
| D. | 1,020 W |
| Answer» D. 1,020 W | |
| 167. |
A common method of cooling a power transformer is? |
| A. | natural air cooling |
| B. | air blast cooling |
| C. | oil cooling |
| D. | any of the above |
| Answer» D. any of the above | |
| 168. |
The secondary of a current transformer is always short-circuited under operating conditions because it? |
| A. | avoids core saturation and high voltage induction |
| B. | is safe to human beings |
| C. | protects the primary circuit |
| D. | none of the above |
| Answer» B. is safe to human beings | |
| 169. |
Efficiency of a power transformer is of the order of? |
| A. | 100 per cent |
| B. | 98 per cent |
| C. | 50 per cent |
| D. | 25 per cent |
| Answer» C. 50 per cent | |
| 170. |
A good voltage regulation of a transformer means? |
| A. | output voltage fluctuation from no load to full load is least |
| B. | output voltage fluctuation with power factor is least |
| C. | difference between primary and secondary voltage is least |
| D. | difference between primary and secondary voltage is maximum |
| Answer» B. output voltage fluctuation with power factor is least | |
| 171. |
The noise resulting from vibrations of laminations set by magnetic forces, is termed as? |
| A. | Magnetostriction |
| B. | Boo |
| C. | Hum |
| D. | Zoom |
| Answer» D. Zoom | |
| 172. |
The maximum efficiency of a distribution transformer is? |
| A. | at no load |
| B. | at 50% full load |
| C. | at 80% full load |
| D. | at full load |
| Answer» C. at 80% full load | |
| 173. |
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are? |
| A. | friction and windage losses |
| B. | copper losses |
| C. | hysteresis and eddy current losses |
| D. | none of the above |
| Answer» D. none of the above | |
| 174. |
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds? |
| A. | 50°C |
| B. | 80°C |
| C. | 100°C |
| D. | 150°C |
| Answer» E. | |
| 175. |
The size of a transformer core will depend on? |
| A. | frequency |
| B. | area of the core |
| C. | flux density of the core material |
| D. | (A) and (B) both |
| Answer» E. | |
| 176. |
The chemical used in breather for transformer should have the quality of? |
| A. | ionizing air |
| B. | absorbing moisture |
| C. | cleansing the transformer oil |
| D. | cooling the transformer oil |
| Answer» C. cleansing the transformer oil | |
| 177. |
A transformer transforms? |
| A. | voltage |
| B. | current |
| C. | power |
| D. | frequency |
| Answer» D. frequency | |
| 178. |
The no load current in a transformer lags behind the applied voltage by an angle of about? |
| A. | 180° |
| B. | 120° |
| C. | 90° |
| D. | 75° |
| Answer» E. | |
| 179. |
If the supply frequency to the transformer is increased, the iron loss will? |
| A. | not change |
| B. | decrease |
| C. | increase |
| D. | any of the above |
| Answer» D. any of the above | |
| 180. |
If a transformer is switched on to a voltage more than the rated voltage? |
| A. | its power factor will deteriorate |
| B. | its power factor will increase |
| C. | its power factor will remain unaffected |
| D. | its power factor will be zero |
| Answer» B. its power factor will increase | |
| 181. |
Transformer breaths in when |
| A. | load on it increases |
| B. | load on it decreases |
| C. | load remains constant |
| D. | none of the above |
| Answer» C. load remains constant | |
| 182. |
Which of the following insulating materials can withstand the highest temperature safely? |
| A. | Cellulose |
| B. | Asbestos |
| C. | Mica |
| D. | Glass fibre |
| Answer» D. Glass fibre | |
| 183. |
A shell-type transformer has |
| A. | high eddy current losses |
| B. | reduced magnetic leakage |
| C. | negligibly hysteresis losses |
| D. | none of the above |
| Answer» C. negligibly hysteresis losses | |
| 184. |
The starting torque of a squirrel-cage induction motor is |
| A. | low |
| B. | negligible |
| C. | same as full-load torque |
| D. | slightly more than full-load torque |
| Answer» B. negligible | |
| 185. |
If R‚ÇÇ is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be$ |
| A. | R‚ÇÇ/‚à öK |
| B. | R₂/K² |
| C. | R₂²/K² |
| D. | R₂²/K |
| Answer» C. R‚Äö√á√ᬨ‚â§/K¬¨‚⧠| |
| 186. |
Greater the secondary leakage flux |
| A. | less will be the secondary induced e.m.f. |
| B. | less will be the primary induced e.m.f. |
| C. | less will be the primary terminal voltage |
| D. | none of the above |
| Answer» B. less will be the primary induced e.m.f. | |
| 187. |
In a transformer routine efficiency depends upon |
| A. | supply frequency |
| B. | load current |
| C. | power factor of load |
| D. | both (B) and (C) |
| Answer» E. | |
| 188. |
The hum in a transformer is mainly attributed to |
| A. | load changes |
| B. | oil in the transformer |
| C. | magnetostriction |
| D. | mechanical vibrations |
| Answer» D. mechanical vibrations | |
| 189. |
Which of the following is the main advantage of an auto-transformer over a two winding transformer? |
| A. | Hysteresis losses are reduced |
| B. | Saving in winding material |
| C. | Copper losses are negligible |
| D. | Eddy losses are totally eliminated |
| Answer» C. Copper losses are negligible | |
| 190. |
Short circuit test on transformers is conducted to determine |
| A. | hysteresis losses |
| B. | copper losses |
| C. | core losses |
| D. | eddy current losses |
| Answer» C. core losses | |
| 191. |
The complete circle diagram of induetion motor can be drawn with the help of data found from |
| A. | noload test |
| B. | blocked rotor test |
| C. | stator resistance test |
| D. | all of the above |
| Answer» E. | |
| 192. |
A transformer can have zero voltage regulation at |
| A. | leading power factor |
| B. | lagging power factor |
| C. | unity power factor |
| D. | zero power factor |
| Answer» B. lagging power factor | |
| 193. |
Iron loss of a transformer can be measured by |
| A. | low power factor wattmeter |
| B. | unity power factor wattmeter |
| C. | frequency meter |
| D. | any type of wattmeter |
| Answer» B. unity power factor wattmeter | |
| 194. |
The efficiencies of transformers compared with that of electric motors of the same power are |
| A. | about the same |
| B. | much smaller |
| C. | much higher |
| D. | somewhat smaller |
| Answer» D. somewhat smaller | |
| 195. |
Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect? |
| A. | Its secondary current is 5 A |
| B. | Its secondary voltage is 400 V |
| C. | Its rating is 2 kVA |
| D. | Its secondary current is 20 A |
| Answer» E. | |
| 196. |
The value of flux involved m the e.m.f. equation of a transformer is |
| A. | average value |
| B. | r.m.s. value |
| C. | maximum value |
| D. | instantaneous value |
| Answer» D. instantaneous value | |
| 197. |
In a transformer the resistance between its primary and secondary should be |
| A. | zero |
| B. | 10 Q |
| C. | 1000 Q |
| D. | infinity |
| Answer» E. | |
| 198. |
The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be |
| A. | 6400 W |
| B. | 1600 W |
| C. | 800 W |
| D. | 400 W |
| Answer» E. | |
| 199. |
The no-load current drawn by transformer is usually what per cent of the full-load current? |
| A. | 0.2 to 0.5 per cent |
| B. | 2 to 5 per cent |
| C. | 12 to 15 per cent |
| D. | 20 to 30 per cent |
| Answer» C. 12 to 15 per cent | |
| 200. |
Hysteresis loss in a transformer varies as (Bmax = maximum flux density) |
| A. | Bmax |
| B. | Bmax1-6 |
| C. | Bmax1-83 |
| D. | B max |
| Answer» C. Bmax1-83 | |