electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
5001. The voltage transformation ratio of a transformer is equal to the ratio of_______________?
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A. secondary terminal voltage to primary applied voltage

B. secondary induced e.m.f. to primary induced e.m.f

C. secondary current to primary current

D. primary turns to secondary turns

5002. Reduction in core losses and increase in permeability are obtained with transformer employing__________?
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A. core built-up of laminations of cold rolled grain oriented steel

B. core built-up of laminations of hot rolled sheet

C. none of the above

D. either of the above

5003. The main reason for generation of harmonics in a transformer could be_______________?
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A. poor insulation

B. fluctuating load

C. saturation of core

D. mechanical vibrations

5004. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
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A. Horn gaps

B. Thermal overload relays

C. Conservator

D. Breather

5005. In the transformer the function of a conservator is to_______________?
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A. none of the above

B. provide fresh air for cooling the transformer

C. protect the transformer from damage when oil expends due to heating

D. supply cooling oil to transformer in time of need

5006. The efficiency of a transformer, under heavy loads, is comparatively low because_______________?
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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

5007. Star/star transformers work satisfactorily when________________?
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A. none of the above

B. load is balanced only

C. on balanced as well as unbalanced loads

D. load is unbalanced only

5008. The use of higher flux density in the transformer design____________?
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A. reduces iron losses

B. reduces copper losses

C. reduces weight per kVA

D. increases part load efficiency

5009. No-load current in a transformer________________?
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A. leads the voltage by about 75

B. leads the voltage by about 15

C. lags behind the voltage by about 15

D. lags behind the voltage by about 75
5010. The purpose of providing iron core in a step-up transformer is?
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A. to provide coupling between primary and secondary

B. to decrease the magnitude of mag-netizing current

C. to increase the magnitude of mutual flux

D. to provide all above features
5011. Which of the following is not a routine test on transformers ?
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A. Impedance test

B. Polarity test

C. Core insulation voltage test

D. Radio interference test
5012. Hysteresis loss in a transformer varies as CBmax = maximum flux density) ?
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A. Bmax1-6

B. Bmax

C. Bmax1-83

D. B max

5013. The transformer laminations are insulated from each other by____________?
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A. mica strip

B. thin coat of varnish

C. paper

D. any of the above

5014. Two transformers operating in parallel will share the load depending upon their____________?
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A. per unit impedance

B. efficiencies

C. ratings

D. leakage reactance

5015. An ideal transformer has infinite values of primary and secondary inductances. The statement is______________?
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A. false

B. TRUE

5016. In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are__________?
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A. hysteresis and eddy current losses

B. friction and windage losses

C. copper losses

D. none of the above

5017. A no-load test is performed on a transformer to determine_______________?
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A. magnetising current and loss

B. core loss

C. efficiency

D. copper loss

E. magnetising current

5018. A transformer can have zero voltage regulation at______________?
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A. leading power factor

B. lagging power factor

C. unity power factor

D. zero power factor

5019. Greater the secondary leakage flux____________?
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A. less will be the primary terminal voltage

B. less will be the secondary induced e.m.f.

C. less will be the primary induced e.m.f.

D. none of the above

5020. The efficiency of two identical transformers under load conditions can be determined by_______________?
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A. open circuit test

B. any of the above

C. back-to-back test

D. short-circuit test

5021. Which of the following is the main advantage of an auto-transformer over a two winding transformer?
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A. Saving in winding material

B. Eddy losses are totally eliminated

C. Copper losses are negligible

D. Hysteresis losses are reduced

5022. Which of the following properties is not necessarily desirable for the material for transformer core ?
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A. High thermal conductivity

B. Low hysteresis loss

C. Adequate mechanical strength

D. High permeability

5023. Which winding in a transformer has more number of turns ?
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A. High voltage winding

B. Low voltage winding

C. Secondary winding

D. Primary winding

5024. If a transformer is continuously operated the maximum temperature rise will occur in_______________?
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A. windings

B. any of the above

C. core

D. tank

5025. For given applied voltage, with the increase in frequency of the applied voltage?
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A. eddy current loss will remain unchanged

B. eddy current loss will decrease

C. eddy current loss will increase

D. none of the above

5026. The transformer oil should have _______ volatility and _______ viscosity?
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A. low,high

B. high,high

C. low,low

D. high,low

5027. In an actual transformer the iron loss remains practically constant from no load to full load because:____________?
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A. secondary voltage remains constant

B. core flux remains practically constant

C. permeability of transformer core remains constant

D. value of transformation ratio remains constant

E. primary voltage remains constant

5028. The degree of mechanical vibrations produced by the laminations of a transformer depends on____________?
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A. gauge of laminations

B. all of the above

C. size of laminations

D. tightness of clamping

5029. Which of the following insulating materials can withstand the highest temperature safely ?
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A. Glass fibre

B. Asbestos

C. Mica

D. Cellulose

5030. The dielectric strength of transformer oil is expected to be______________?
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A. 33 kV

B. lkV

C. 100 kV

D. 330 kV

5031. In a transformer routine efficiency depends upon_____________?
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A. supply frequency

B. load current

C. power factor of load

D. both B. and (c)
5032. While conducting short-circuit test on a transformer the following side is short circuited?
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A. Primary side

B. Low voltage side

C. Secondary side

D. High voltage side

5033. The permissible flux density in case of cold rolled grain oriented steel is around__________?
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A. 1.7 Wb/m2

B. 3.7 Wb/m2

C. 2.7 Wb/m2

D. 4.7 Wb/m2

5034. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?
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A. loading of the transformers not in proportion to their kVA ratings

B. power factor of one of the transformers is leading while that of the other lagging

C. transformers having higher copper losses will have negligible core losses

D. short-circuiting of the secondaries

5035. Distribution transformers are generally designed for maximum efficiency around________________?
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A. 90% load

B. zero load

C. 50% load

D. 25% load

5036. Transformer breaths in when_______________?
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A. load remains constant

B. load on it decreases

C. load on it increases

D. none of the above

5037. During short circuit test iron losses are negligible because of _____________?
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A. full-load current is not supplied to the transformer

B. the voltage applied on primary side is low

C. the current on secondary side is negligible

D. the voltage on secondary side does not vary

5038. The chemical used in breather for transformer should have the quality of____________?
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A. ionizing air

B. cleansing the transformer oil

C. absorbing moisture

D. cooling the transformer oil

5039. Sumpners test is conducted on transformers to determine_____________?
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A. none of the above

B. temperature

C. stray losses

D. all-day efficiency

5040. The no-load current drawn by transformer is usually what per cent of the full-load current ?
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A. 20 to 30 per cent

B. 0.2 to 0.5 per cent

C. 2 to 5 per cent

D. 12 to 15 per cent

5041. No-load on a transformer is carried out to determine______________?
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A. efficiency of the transformer

B. magnetising current and loss

C. magnetising current

D. copper loss

5042. If R2 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___________?
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A. R2IK2

B. R22!K2

C. R22/K

D. R2/VK

5043. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?
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A. Bushings

B. Conservator

C. Buchholz relay

D. Breather

5044. When secondary of a current transformer is open-circuited its iron core will be__________?
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A. none of above will happen

B. hot because of heavy iron losses taking place in it due to high flux density

C. hot because primary will carry heavy current

D. cool as there is no secondary current

5045. Which of the following does not change in an ordinary transformer ?
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A. Voltage

B. Frequency

C. Current

D. Any of the above

5046. Silicon steel used in laminations mainly reduces___________?
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A. all of the above

B. copper losses

C. hysteresis loss

D. eddy current losses

5047. A Buchholz relay can be installed on______________?
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A. air-cooled transformers

B. oil cooled transformers

C. uchholz relay can be installed on

D. auto-transformers

E. welding transformers

5048. Which of the following is the most likely source of harmonics in a transformer ?
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A. Overload

B. loose connections

C. poor insulation

D. Core saturation
5049. The leakage flux in a transformer depends upon______________?
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A. load current, voltage, frequency and power factor

B. load current

C. load current and voltage

D. load current, voltage and frequency

5050. For a transformer, operating at constant load current, maximum efficiency will occur at______________?
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A. 0.8 lagging power factor

B. 0.8 leading power factor

C. unity power factor

D. zero power factor