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.
| 101. |
_ The function of breather in a transformer is$? |
| A. | to provide oxygen inside the tank |
| B. | to cool the coils during reduced load |
| C. | to cool the transformer oil |
| D. | to arrest flow of moisture when outside air enters the transformer |
| Answer» E. | |
| 102. |
_ A transformer can have regulation closer to zero$? |
| A. | on full-load |
| B. | on overload |
| C. | on leading power factor |
| D. | on zero power factor |
| Answer» D. on zero power factor | |
| 103. |
_ For a transformer, operating at constant load current, maximum efficiency will occur at$? |
| A. | 0.8 leading power factor |
| B. | 0.8 lagging power factor |
| C. | zero power factor |
| D. | unity power factor |
| Answer» E. | |
| 104. |
_ Minimum voltage regulation occurs when the power factor of the load is$? |
| A. | unity |
| B. | lagging |
| C. | leading |
| D. | zero |
| Answer» D. zero | |
| 105. |
_ The degree of mechanical vibrations produced by the laminations of a transformer depends on$? |
| A. | tightness of clamping |
| B. | gauge of laminations |
| C. | size of laminations |
| D. | all of the above |
| Answer» E. | |
| 106. |
_ In a power or distribution transformer about 10 per cent end turns are heavily insulated$? |
| A. | to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns |
| B. | to absorb the line surge voltage and save the winding of transformer from damage |
| C. | to reflect the line surge and save the winding of a transformer from damage |
| D. | none of the above |
| Answer» B. to absorb the line surge voltage and save the winding of transformer from damage | |
| 107. |
_ Natural oil cooling is used for transformers up to a rating of$? |
| A. | 3000 kVA |
| B. | 1000 kVA |
| C. | 500 kVA |
| D. | 250 kVA |
| Answer» B. 1000 kVA | |
| 108. |
_ The main reason for generation of harmonics in a transformer could be$? |
| A. | fluctuating load |
| B. | poor insulation |
| C. | mechanical vibrations |
| D. | saturation of core |
| Answer» E. | |
| 109. |
_ Distribution transformers are generally designed for maximum efficiency around$? |
| A. | 90% load |
| B. | Zero load |
| C. | 25% load |
| D. | 50% load |
| Answer» E. | |
| 110. |
__In a transformer the tappings are generally provided on__ |
| A. | primary side |
| B. | secondary side |
| C. | low voltage side |
| D. | high voltage side |
| Answer» E. | |
| 111. |
__During short circuit test iron losses are negligible because__ |
| A. | the current on secondary side is negligible |
| B. | the voltage on secondary side does not vary |
| C. | the voltage applied on primary side is low |
| D. | full-load current is not supplied to the transformer |
| Answer» D. full-load current is not supplied to the transformer | |
| 112. |
__Which of the following does not change in an ordinary transformer?__ |
| A. | Frequency |
| B. | Voltage |
| C. | Current |
| D. | Any of the above |
| Answer» B. Voltage | |
| 113. |
__In the transformer following winding has got more cross-sectional area__ |
| A. | Low voltage winding |
| B. | High voltage winding |
| C. | Primary winding |
| D. | Secondary winding |
| Answer» B. High voltage winding | |
| 114. |
__The dielectric strength of transformer oil is expected to be__ |
| A. | lkV |
| B. | 33 kV |
| C. | 100 kV |
| D. | 330 kV |
| Answer» C. 100 kV | |
| 115. |
__Noise level test in a transformer is a__ |
| A. | special test |
| B. | routine test |
| C. | type test |
| D. | none of the above |
| Answer» D. none of the above | |
| 116. |
__Negative voltage regulation is indicative that the load is__ |
| A. | capacitive only |
| B. | inductive only |
| C. | inductive or resistive |
| D. | none of the above |
| Answer» B. inductive only | |
| 117. |
__The permissible flux density in case of cold rolled grain oriented steel is around__ |
| A. | 1.7 Wb/m² |
| B. | 2.7 Wb/m² |
| C. | 3.7 Wb/m² |
| D. | 4.7 Wb/m² |
| Answer» B. 2.7 Wb/m¬¨‚⧠| |
| 118. |
__Which of the following acts as a protection against high voltage surges due to lightning and switching?__ |
| A. | Horn gaps |
| B. | Thermal overload relays |
| C. | Breather |
| D. | Conservator |
| Answer» B. Thermal overload relays | |
| 119. |
__An open-circuit test on a transformer is conducted primarily to measure__ |
| A. | insulation resistance |
| B. | copper loss |
| C. | core loss |
| D. | total loss |
| Answer» D. total loss | |
| 120. |
__The 'cogging' of an induction motor can be avoided by__ |
| A. | proper ventilation |
| B. | using DOL starter |
| C. | auto-transformer starter |
| D. | having number of rotor slots more or less than the number of stator slots (not equal) |
| Answer» E. | |
| 121. |
__Which of the following property is not necessarily desirable in the material for transformer core?__ |
| A. | Mechanical strength |
| B. | Low hysteresis loss |
| C. | High thermal conductivity |
| D. | High permeability |
| Answer» D. High permeability | |
| 122. |
_If the percentage impedances of the two transformers working in parallel are different, then$? |
| A. | transformers will be overheated |
| B. | power factors of both the transformers will be same |
| C. | parallel operation will be not possible |
| D. | parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load |
| Answer» E. | |
| 123. |
_The power transformer is a constant$? |
| A. | voltage device |
| B. | current device |
| C. | power device |
| D. | main flux device |
| Answer» E. | |
| 124. |
_Which of the following protection is normally not provided on small distribution transformers?$? |
| A. | Overfluxing protection |
| B. | Buchholz relay |
| C. | Overcurrent protection |
| D. | All of the above |
| Answer» C. Overcurrent protection | |
| 125. |
_The changes in volume of transformer cooling oil due to variation of atmospheric tem-perature during day and night is taken care of by which part of transformer$? |
| A. | Conservator |
| B. | Breather |
| C. | Bushings |
| D. | Buchholz relay |
| Answer» B. Breather | |
| 126. |
_For given applied voltage, with the increase in frequency of the applied voltage$? |
| A. | eddy current loss will decrease |
| B. | eddy current loss will increase |
| C. | eddy current loss will remain unchanged |
| D. | none of the above |
| Answer» D. none of the above | |
| 127. |
_A transformer cannot raise or lower the voltage of a D.C. supply because$? |
| A. | There is no need to change the D.C. voltage |
| B. | A D.C. circuit has more losses |
| C. | Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero |
| D. | None of the above |
| Answer» D. None of the above | |
| 128. |
_The function of conservator in a transformer is$? |
| A. | to project against internal fault |
| B. | to reduce copper as well as core losses |
| C. | to cool the transformer oil |
| D. | to take care of the expansion and contraction of transformer oil due to variation of temper-ature of sur-roundings |
| Answer» E. | |
| 129. |
_In a transformer the resistance between its primary and secondary is$? |
| A. | zero |
| B. | 1 ohm |
| C. | 1000 ohms |
| D. | infinite |
| Answer» E. | |
| 130. |
_The efficiency of two identical transformers under load conditions can be determined by$? |
| A. | short-circuit test |
| B. | back-to-back test |
| C. | open circuit test |
| D. | any of the above |
| Answer» C. open circuit test | |
| 131. |
_The term 'cogging' is associated with$? |
| A. | three phase transformers |
| B. | compound generators |
| C. | series motors |
| D. | induction motors |
| Answer» E. | |
| 132. |
_The transformer oil should have _____ volatility and _____ viscosity.$? |
| A. | low,low |
| B. | high,high |
| C. | low,high |
| D. | high,low |
| Answer» B. high,high | |
| 133. |
The efficiency of a transformer, under heavy loads, is comparatively low because$? |
| A. | copper loss becomes high in proportion to the output |
| B. | iron loss is increased considerably |
| C. | voltage drop both in primary and secondary becomes large |
| D. | secondary output is much less as compared to primary input |
| Answer» B. iron loss is increased considerably | |
| 134. |
Material used for construction of transformer core is usually$? |
| A. | wood |
| B. | copper |
| C. | aluminium |
| D. | silicon steel |
| Answer» E. | |
| 135. |
In case of 3-phase induction motors, plugging means$? |
| A. | pulling the motor directly on line without a starter |
| B. | locking of rotor due to harmonics |
| C. | starting the motor on load which is more than the rated load |
| D. | interchanging two supply phases for quick stopping |
| Answer» E. | |
| 136. |
In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be$? |
| A. | Ns |
| B. | s.N. |
| C. | (l-s)Ns |
| D. | (Ns-l)s |
| Answer» D. (Ns-l)s | |
| 137. |
A transformer transforms$? |
| A. | voltage |
| B. | current |
| C. | power |
| D. | frequency |
| Answer» D. frequency | |
| 138. |
If a transformer is switched on to a voltage more than the rated voltage$? |
| 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 | |
| 139. |
The no load current in a transformer lags behind the applied voltage by an angle of about$? |
| A. | 180° |
| B. | 120° |
| C. | 90° |
| D. | 75° |
| Answer» E. | |
| 140. |
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are$? |
| 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 | |
| 141. |
The chemical used in breather for transformer should have the quality of$? |
| A. | ionizing air |
| B. | absorbing moisture |
| C. | cleansing the transformer oil |
| D. | cooling the transformer oil |
| Answer» C. cleansing the transformer oil | |
| 142. |
If the supply frequency to the transformer is increased, the iron loss will$? |
| A. | not change |
| B. | decrease |
| C. | increase |
| D. | any of the above |
| Answer» D. any of the above | |
| 143. |
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds$? |
| A. | 50°C |
| B. | 80°C |
| C. | 100°C |
| D. | 150°C |
| Answer» E. | |
| 144. |
The size of a transformer core will depend on$? |
| A. | frequency |
| B. | area of the core |
| C. | flux density of the core material |
| D. | (A) and (B) both |
| Answer» E. | |
| 145. |
A transformer core is laminated to$? |
| A. | reduce hysteresis loss |
| B. | reduce eddy current losses |
| C. | reduce copper losses |
| D. | reduce all above losses |
| Answer» C. reduce copper losses | |
| 146. |
Two transformers operating in parallel will share the load depending upon their$? |
| A. | leakage reactance |
| B. | per unit impedance |
| C. | efficiencies |
| D. | ratings |
| Answer» C. efficiencies | |
| 147. |
While conducting short-circuit test on a transformer the following side is short circuited$? |
| A. | High voltage side |
| B. | Low voltage side |
| C. | Primary side |
| D. | Secondary side |
| Answer» C. Primary side | |
| 148. |
A transformer has a 1:6 turns ratio and a secondary coil load resistance of 470 Ω. The load resistance as seen by the source is$? |
| A. | 1.3 Ω |
| B. | 7.8 Ω |
| C. | 78 Ω |
| D. | 13 Ω |
| Answer» E. | |
| 149. |
A good voltage regulation of a transformer means$? |
| A. | output voltage fluctuation from no load to full load is least |
| B. | output voltage fluctuation with power factor is least |
| C. | difference between primary and secondary voltage is least |
| D. | difference between primary and secondary voltage is maximum |
| Answer» B. output voltage fluctuation with power factor is least | |
| 150. |
No-load on a transformer is carried out to determine$? |
| A. | copper loss |
| B. | magnetising current |
| C. | magnetising current and loss |
| D. | efficiency of the transformer |
| Answer» D. efficiency of the transformer | |