| 1. | Which of the following insulating materials is used in power transformers ? | |
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Tape of glass
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Synthetic resin bonded paper
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Press board
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All of the above
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Report Question| 2. | A transformer designed for installation in a tropical country if installed in a cold country ? | |
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is to be loaded below the name plate KVA rating
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can-be loaded in excess of the name plate kVA rating
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either of the above
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neither of the above
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| 3. | The output current corresponding to the maximum efficiency for a transformer having core loss of 200 W and equivalent resistance referred to secondary of 0.5 ? is ? | |
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5 A
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10 A
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15 A
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20 A
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| 4. | All day efficiency is the ratio of output to input in ? | |
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kVA at a particular instant
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kW at particular instant
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kVARh at particular instant
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KWb during 24 hours
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| 5. | When 240 V D.C. supply is given to an unloaded 220 V, 50 Hz transformer ? | |
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secondary will carry heavy current
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primary will carry heavy current and may possibly burn
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we will get A.C. voltage on secondary side according to turn ratio
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we will get high voltage on secondary side
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| 6. | The magnetizing current, for sinusoidal voltage applied, will be ? | |
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always sinusoidal
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always non-sinusoidal
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sinusoidal or non-sinusoidal depending upon the saturation point
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none of the above
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| 7. | For power purpose sine wave shape is preferred because ? | |
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it gives least copper losses
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it is easy to generate e.m.f. of this wave shape
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it is stable wave shape as the line parameters cannot change it
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none of the above
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| 8. | In case of transformers using cold rolled grain oriented steel, the area of yoke is taken ? | |
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equal to that of core
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as 10-15% larger than that of core
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as 15-20% larger than that of core
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as 20-25% larger than that of core
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| 9. | For a transformer, operating at constant load current, maximum efficiency will occur at ? | |
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0.8 leading power factor
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0.8 lagging power factor
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zero power factor
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unity power factor
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| 10. | In an actual transformer the iron loss remains practically constant from no load to full-load because ? | |
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value of transformation ratio remains constant
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permeability of transformer core remains constant
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core flux remains practically constant
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primary voltage remains constant
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