MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 354 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
If a portion of armature current is diverted through the diverter resistance, then the speed of d.c. series motor |
| A. | Remains same |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 252. |
If A is the number of parallel paths and P is the number of poles, then the number of parallel path in lap winding and in wave winding is |
| A. | A = P, A = 2 |
| B. | A = 2P, A = P |
| C. | A = 2, A = P |
| D. | A = P, A = 2P |
| Answer» B. A = 2P, A = P | |
| 253. |
If a d.c. series motor is started on very light load or on no load then |
| A. | It will run at dangerously high speed which may damage the motor mechanically |
| B. | It will run at very low speed |
| C. | Load does not effect the speed of d.c. series motor |
| D. | None of these |
| Answer» B. It will run at very low speed | |
| 254. |
If a 3 phase alternator is short circuited at its terminal, then the initial value of short circuit current will be limited by |
| A. | Synchronous reactance |
| B. | Transient reactance |
| C. | Sub transient reactance |
| D. | All of the above |
| Answer» D. All of the above | |
| 255. |
Hunting in a synchronous motor results in |
| A. | Loss of synchronism |
| B. | Mechanical and electrical stresses on motor |
| C. | Large current drawn by motor |
| D. | all of the above |
| E. | None of the above |
| Answer» E. None of the above | |
| 256. |
Generally the effective resistance of alternator under a.c. condition is taken as |
| A. | Less than 1.25 times the d.c. resistance |
| B. | 1.25 to 1.75 times the d.c. resistance |
| C. | Greater than 1.75 times the d.c. resistance |
| D. | None of these |
| Answer» C. Greater than 1.75 times the d.c. resistance | |
| 257. |
Generally, in alternator divided winding rotor is preferred to a conventional winding rotor, because it gives |
| A. | Better damping |
| B. | Less harmonics |
| C. | More efficiency |
| D. | None of these |
| Answer» B. Less harmonics | |
| 258. |
Functions of commutator in d.c. machines are |
| A. | To facilitate the collection of current from armature conductors |
| B. | To convert internally developed induced emf to unidirectional emf |
| C. | To produce unidirectional torque in case of motors |
| D. | All of these |
| E. | None of these |
| Answer» E. None of these | |
| 259. |
For transformers ratings are always given in kVA, not in kW because |
| A. | It is conventional |
| B. | Power factor of load is not known |
| C. | For higher efficiency |
| D. | To make calculation simple |
| Answer» C. For higher efficiency | |
| 260. |
For the speed control of squirrel cage induction motor, the most suitable method is |
| A. | Rotor resistance control |
| B. | Rotor reactance control |
| C. | Stator resistance control |
| D. | Stator reactance control |
| Answer» B. Rotor reactance control | |
| 261. |
For the star - star connection of three phase transformer, the phase angle between the phase voltages and line voltages on both primary and secondary side is |
| A. | 0 degree |
| B. | 30 degree |
| C. | 60 degree |
| D. | 120 degree |
| Answer» C. 60 degree | |
| 262. |
For the same excitation voltage and winding currents, the autotransformer gives |
| A. | Less output than two winding transformer |
| B. | Equal to the output of two winding transformer |
| C. | Half of the output of two winding transformer |
| D. | More than the output of the two winding transformer |
| Answer» E. | |
| 263. |
For the protection of d.c. series motor, which starter is commonly used? |
| A. | Two point starter |
| B. | Three point starter |
| C. | Four point starter |
| D. | None of these |
| Answer» B. Three point starter | |
| 264. |
For the construction of the armature of a d.c. machine, the best suited material is |
| A. | Cast iron |
| B. | Silicon steel |
| C. | Carbon |
| D. | All of these |
| Answer» C. Carbon | |
| 265. |
For the calculation of induced emf in a transformer the flux used in the equation is in its |
| A. | RMS value |
| B. | Average value |
| C. | Maximum value |
| D. | Double of its maximum value |
| Answer» D. Double of its maximum value | |
| 266. |
For synchronization of single phase alternators which method gives the more accurate result? |
| A. | Lamps dark method |
| B. | Lamps bright method |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» C. Both (a) and (b) | |
| 267. |
For synchronization of alternators, the most suitable method is |
| A. | Lamps method |
| B. | Voltmeter |
| C. | Synchroscope |
| D. | None of the above |
| Answer» D. None of the above | |
| 268. |
For slip s of an induction motor, the ratio of rotor copper loss to the gross mechanical output is |
| A. | 1 / ( 1 - s) |
| B. | 1 / s |
| C. | ( 1 - s ) / s |
| D. | s / ( 1 - s ) |
| Answer» E. | |
| 269. |
For satisfactory parallel operation, the circulating current should not exceed |
| A. | 5% of normal rated current |
| B. | 50% of normal rated current |
| C. | 10% of normal rated current |
| D. | 25% of normal rated current |
| Answer» D. 25% of normal rated current | |
| 270. |
For reducing the slot harmonics in an alternator, the length of air gap is |
| A. | Reduced |
| B. | Increased |
| C. | Not related to harmonics |
| D. | None of these |
| Answer» C. Not related to harmonics | |
| 271. |
For plotting circle diagram no load power factor is required. The value of no load power factor will be |
| A. | Lesser than 0.5 |
| B. | Greater than 0.5 |
| C. | Equal to 0.5 |
| D. | 1 |
| Answer» B. Greater than 0.5 | |
| 272. |
For performing Hopkinson’s test two identical machines are required which are mechanically coupled. The iron losses in the two machines |
| A. | Can be obtained separately |
| B. | Cannot be separated |
| Answer» C. | |
| 273. |
For parallel operation of transformers, the p.u. impedances of transformer must be (based on their own kVA rating) |
| A. | directly proportional to their ratings |
| B. | inversely proportional to their ratings |
| C. | equal |
| D. | none of these |
| Answer» D. none of these | |
| 274. |
For parallel operation of transformers, the most satisfactory condition is achieved when the load shared by the transformers is in exact proportion with their |
| A. | Efficiency |
| B. | Ratings |
| C. | Impedances |
| D. | None of these |
| Answer» C. Impedances | |
| 275. |
For moment of inertia to be small in two phase servomotor, the ratio of rotor diameter to its length should be |
| A. | Equal to 1 |
| B. | small |
| C. | large |
| D. | All of these |
| Answer» C. large | |
| 276. |
For maximum torque, the only parameter which controls the torque is slip. The maximum torque is |
| A. | directly proportional to the rotor resistance |
| B. | inversely proportional to the rotor resistance |
| C. | directly proportional to the slip times the rotor resistance |
| D. | independent of the rotor resistance |
| Answer» E. | |
| 277. |
For maximum efficiency in a transformer |
| A. | Core losses = 2 * copper losses |
| B. | Core losses = copper losses / 2 |
| C. | Core losses = copper losses |
| D. | Core losses = copper losses ∧ 2 |
| Answer» D. Core losses = copper losses ∧ 2 | |
| 278. |
For low reluctance path for the flux in armature, the permeability of the material should be |
| A. | High |
| B. | Low |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» C. Both (a) and (b) | |
| 279. |
For high capacity alternators, which method is not suitable for finding percentage regulation? |
| A. | Direct loading method |
| B. | Synchronous impedance method |
| C. | Ampere-turns method |
| D. | Potier triangle method |
| Answer» B. Synchronous impedance method | |
| 280. |
For frequent starting, stopping and reversals, which motor is commonly used? |
| A. | Permanent d.c. motor |
| B. | Ward-Leonard system |
| C. | Brushless d.c. motor |
| D. | All of these |
| Answer» C. Brushless d.c. motor | |
| 281. |
For finding voltage regulation of an alternator, the method which gives most accurate result is |
| A. | E.M.F method |
| B. | M.M.F. method |
| C. | Z.P.F method |
| D. | ASA modification of M.M.F. method |
| Answer» D. ASA modification of M.M.F. method | |
| 282. |
For critical excitation the power factor of the synchronous motor will be equal to |
| A. | 0 |
| B. | 1 |
| C. | 0.5 MΩ |
| D. | None of the above |
| Answer» C. 0.5 MΩ | |
| 283. |
For conducting no load test on an induction motor two wattmeter’s are required. Readings of the meters |
| A. | Both will be positive |
| B. | One will be positive and other will be negative |
| C. | Both will be negative |
| D. | None of these |
| Answer» C. Both will be negative | |
| 284. |
For connecting the rotating member of machine to the external stationary circuit, |
| A. | Slip rings and brush assembly is used |
| B. | Only slip ring is used |
| C. | Only brushes are used |
| D. | Directly connected to the external stationary circuit |
| Answer» B. Only slip ring is used | |
| 285. |
For carrying out parallel operation, transformers should have same X / R ratio in order to avoid |
| A. | Leakage reactance |
| B. | Insulation failure |
| C. | Circulating current |
| D. | Inrush current |
| Answer» D. Inrush current | |
| 286. |
For an ideal transformer winding resistances and leakage flux should be |
| A. | Least, maximum |
| B. | Both should be maximum |
| C. | Both should be zero |
| D. | Maximum, least |
| Answer» D. Maximum, least | |
| 287. |
For a two pole, 50 Hz, 3 phase synchronous motor the speed of rotating magnetic field is |
| A. | 1000 rpm |
| B. | 2000 rpm |
| C. | 3000 rpm |
| D. | 3500 rpm |
| Answer» D. 3500 rpm | |
| 288. |
For a transformer, permeability and hysteresis loss should be |
| A. | Low, low |
| B. | Low, high |
| C. | High, low |
| D. | High, high |
| Answer» D. High, high | |
| 289. |
For a three phase induction motor, the two rotor frequencies are given by |
| A. | sf, (1 - s) f |
| B. | sf, (2 - s) f |
| C. | (1 - s) f, (2 - s) f |
| D. | Sf , sf |
| Answer» C. (1 - s) f, (2 - s) f | |
| 290. |
For a synchronous motor, as the load angle reaches up to 90 ° electrical i.e. half a pole pitch, then the magnetic locking between the stator and rotor |
| A. | No longer exist |
| B. | Will be strongest |
| C. | Will be weakest |
| D. | None of these |
| Answer» B. Will be strongest | |
| 291. |
For a single phase no load transformer, which among the following losses will be minimum? |
| A. | hysteresis losses |
| B. | eddy current losses |
| C. | copper losses |
| D. | mechanical losses |
| Answer» D. mechanical losses | |
| 292. |
For a short pitch and distributed winding, the value of coil span factor and distributed factor |
| A. | Both are less than unity |
| B. | Less than unity, greater than unity |
| C. | Greater then unity, less than unity |
| D. | Both are greater than unity |
| Answer» B. Less than unity, greater than unity | |
| 293. |
For a half cycle of fluxes in a synchronous motor, the resultant flux has rotated through |
| A. | 0 degree |
| B. | 90 degree |
| C. | 180 degree |
| D. | 360 degree |
| Answer» D. 360 degree | |
| 294. |
For a constant torque load, if the armature resistance of shunt motor is doubled (keeping the shunt field constant) then the armature current will |
| A. | Double |
| B. | Get halved |
| C. | Remain same |
| D. | None of these |
| Answer» D. None of these | |
| 295. |
For a certain transformer if E1 is the emf across primary winding, E2 is the emf across secondary winding and K is the ratio of secondary to primary turns. The value of secondary emf referred to the primary side is |
| A. | E2 / K |
| B. | E2 / K ∧ 2 |
| C. | K * E2 |
| D. | K ∧ 2 * E2 |
| Answer» B. E2 / K ∧ 2 | |
| 296. |
Electrical power output in a d.c. generator is equal to |
| A. | Electrical power developed in armature – copper losses |
| B. | Mechanical power input – iron and friction losses |
| C. | Electrical power developed in armature – iron and copper losses |
| D. | Mechanical power input – iron and friction losses – copper losses |
| Answer» E. | |
| 297. |
During the one complete revolution of the conductor in a 4 pole synchronous generator, induced emf will experience |
| A. | Two times maxima and two times zero |
| B. | Two times maxima and four times zero |
| C. | Eight times maxima and eight times zero |
| D. | Four times maxima and four times zero |
| Answer» E. | |
| 298. |
During starting, the magnetic field produced in a transformer is |
| A. | 1.5 times the maximum |
| B. | Equal to the maximum |
| C. | 0.5 times of the maximum |
| D. | Equal to zero |
| Answer» E. | |
| 299. |
Due to the effect of armature reaction in d.c. machine, the value of generated voltage and flux per pole |
| A. | Increases, decreases |
| B. | Decreases, decreases |
| C. | Decreases, increases |
| D. | Increases, increases |
| Answer» C. Decreases, increases | |
| 300. |
Due to short pitching, the induced emf gets |
| A. | Reduced |
| B. | Increased |
| C. | Remains same |
| D. | None of these |
| Answer» B. Increased | |