MCQOPTIONS
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MCQOPTIONS
This section includes 123 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. |
Transformers are rated in KVA instead of KW because |
| A. | load power factor is often not known |
| B. | KVA is fixed whereas KW depends on load power factor |
| C. | Total transformer loss depends on volt ampere |
| D. | It has become customary |
| Answer» D. It has become customary | |
| 102. |
No load test on a transformer is carried out to find |
| A. | copper loss |
| B. | magnetising current |
| C. | magnetising current and no load loss |
| D. | efficiency of the transformer |
| Answer» D. efficiency of the transformer | |
| 103. |
The ordinary two winding transformer's primary and secondary windings always have |
| A. | different no of turns |
| B. | same size of copper wire |
| C. | a common magnetic circuit |
| D. | separate magnetic circuits |
| Answer» D. separate magnetic circuits | |
| 104. |
the main purpose of using core in a transformer is to |
| A. | Decrease iron losses |
| B. | prevent eddy current loss |
| C. | eliminate magnetic hysteresis |
| D. | decrease reluctance of the common magnetic circuit |
| Answer» E. | |
| 105. |
Transformer cores are built up from laminations rather than from solid metal so that |
| A. | . Oil penetrates the core more easily |
| B. | Eddy current loss is reduced |
| C. | Less lamination is required for the windings |
| D. | Turn ratio is higher than voltage ratio |
| Answer» C. Less lamination is required for the windings | |
| 106. |
The transformer core is laminated to |
| A. | Reduce the copper losses |
| B. | Reduce the core losses |
| C. | Reduce the eddy current losses |
| D. | None of the above |
| Answer» D. None of the above | |
| 107. |
Which type of loss is not common to transformer and rotating machines? |
| A. | Eddy current loss |
| B. | Copper loss |
| C. | Hysteresis loss |
| D. | Windage loss |
| Answer» E. | |
| 108. |
A step-up transformer increases |
| A. | voltage |
| B. | current |
| C. | power |
| D. | frequency |
| Answer» B. current | |
| 109. |
The efficiency of a transformer is maximum when |
| A. | It runs at half full load |
| B. | it runs at full load |
| C. | its Cu loss equal iron loss |
| D. | it runs over load |
| Answer» D. it runs over load | |
| 110. |
The frequency of the secondary voltage of a transformer will be..... |
| A. | less than frequency of the primary voltage |
| B. | equal to the primary voltage |
| C. | greater than the frequency of the primary voltage |
| D. | much greater than the frequency of the primary voltage |
| Answer» C. greater than the frequency of the primary voltage | |
| 111. |
In an ideal transformer |
| A. | windings have no resistance |
| B. | core has no losses |
| C. | core has infinite permeability |
| D. | all of the above |
| Answer» E. | |
| 112. |
Which is not the basic element of the transformer? |
| A. | core |
| B. | primary winding |
| C. | secondary winding |
| D. | mutual flux |
| Answer» E. | |
| 113. |
A transformer transforms |
| A. | frequency |
| B. | voltage |
| C. | current |
| D. | voltage and current |
| Answer» E. | |
| 114. |
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. | |
| 115. |
Which of the following properties 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 | |
| 116. |
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 | |
| 117. |
The main advantage of auto transformer over a two winding transformer is |
| 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 | |
| 118. |
The value of flux involved in the emf equation of a transformer is |
| A. | rms value |
| B. | rms value |
| C. | Maximum value |
| D. | Instantaneous value |
| Answer» D. Instantaneous value | |
| 119. |
The transformer ratings are usually expressed in terms of |
| A. | Volts |
| B. | Amperes |
| C. | kW |
| D. | kVA |
| Answer» E. | |
| 120. |
Helical coils can be used on |
| A. | Low voltage side of high kVA transformers |
| B. | High frequency transformers |
| C. | High voltage side of small capacity transformer |
| D. | High voltage side of high kVA rating transformers |
| Answer» B. High frequency transformers | |
| 121. |
Material used for construction of transformer core is usually |
| A. | 0.4mm to 0.5 mm |
| B. | . 4mm to 5 mm |
| C. | . 14mm to 15 mm |
| D. | 25mm to 40 mm |
| Answer» E. | |
| 122. |
The chemical used in breather is |
| A. | Asbestos fibre |
| B. | Silica sand |
| C. | Sodium chloride |
| D. | Silica gel |
| Answer» E. | |
| 123. |
A Buchholz relay can be installed on |
| A. | Auto-transformers |
| B. | Air-cooled transformers |
| C. | Welding transformers |
| D. | Oil cooled transformers |
| Answer» E. | |