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
201. If all the SCRs of 3 phase PAC is replaced by diodes, they would be triggered_____________?
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A. 60 degree before the zero crossing of the corresponding line voltages

B. 60 degree after the zero crossing of the corresponding line voltages

C. 120 degree after the zero crossing of the corresponding line voltages

D. 120 degree before the zero crossing of the corresponding line voltages

202. The power transformer is a constant______________?
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A. main flux device

B. power device

C. current device

D. voltage device

203. 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
204. If the supply frequency to the transformer is increased,the iron loss will__________?
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A. not change

B. increase

C. any of the above

D. decrease

205. Advantages of Cuk converter is / are_____________?
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A. Low stress on switch

B. None of these

C. Low stress on capacitor

D. Large number of reactive component

206. Which of the following material has nearly zero temperature co-efficient of resistance_________?
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A. Manganin

B. Carbon

C. Copper

D. Porcelain

207. Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be_________________?
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A. 3 times

B. 1/9 times

C. 1/3 times

D. 9 times

208. You have to replace 1500 Q resistor in radio. You have no 1500 Q resistor but have several 1000 Q ones which you would connect__________?
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A. three in parallel

B. two in parallel

C. three in series

D. two in parallel and one in series
209. A full wave rectifier with resistive load produces___________?
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A. Second harmonic

B. Fifth harmonic

C. Do not produce harmonics

D. Third harmonic

210. A TRIAC can be turned on with______________?
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A. Negative voltage at the gate terminal

B. Positive voltage at the gate terminal

C. Either (a) or (b)

D. None of these

211. The maximum efficiency of a distribution transformer is____________?
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A. at no load

B. at 50% full load

C. at full load

D. at 80% full load

212. Bidirectional semiconductor device is___________?
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A. BJT

B. TRIAC

C. SCR

D. Diode

213. The noise resulting from vibrations of laminations set by magnetic forces, is termed as_________________?
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A. magnetostrication

B. boo

C. hum

D. zoom

214. 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

215. The phase angle of gate signal in TRIAC can be shifted by using_____________?
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A. An inductor

B. Only (a) and (b)

C. A variable resistor

D. A capacitor

216. Whether circuit may be AC. or D. C. one, following is most effective in reducing the magnitude of the current?
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A. Reactor

B. Inductor

C. Capacitor

D. Resistor
217. The dielectric strength of transformer oil is expected to be______________?
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A. lkV

B. 33 kV

C. 330 kV

D. 100 kV

218. Which of the following properties is not necessarily desirable for the material for transformer core ?
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A. High permeability

B. Low hysteresis loss

C. Adequate mechanical strength

D. High thermal conductivity
219. Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be_____________?
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A. 10 ohms

B. 80 ohms

C. 20 ohms

D. 160 ohms

220. The magnetising current of a transformer is usually small because it has___________?
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A. small air gap

B. laminated silicon steel core

C. fewer rotating parts

D. large leakage flux

221. One newton meter is same as_____________?
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A. one joule

B. one joule second

C. one watt

D. five joules

222. A resistance having rating 10 ohms, 10 W is likely to be a__________?
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A. variable resistor

B. carbon resistor

C. metallic resistor

D. wire wound resistor
223. A MOSFET, for its conduction uses_____________?
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A. Only minority carriers

B. Only majority carriers

C. Both minority and majority carriers

D. None of these

224. 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. 12 to 15 per cent

C. 0.2 to 0.5 per cent

D. 2 to 5 per cent
225. The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around_______________?
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A. 1.8 x 10?8 Q-m

B. 1.6 x 10?8 Q-m

C. 1.4 x 10~8 Q-m

D. 1.2 x 10~8 Q-m

226. Silicon controlled rectifier can be turned on____________?
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A. By making current non zero and turned off by making current zero

B. And turned off by applying gate pulse

C. By applying a gate pulse and turned off by removing the gate pulse

D. By applying a gate pulse and turned off only when current becomes zero
227. Which of the following loss in a transformer is zero even at full load ____________?
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A. Friction loss

B. Core loss

C. Hysteresis loss

D. Eddy current loss

228. In the SPWM, the modulating signal is___________?
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A. Triangular

B. Square

C. Saw tooth

D. Sinusoidal
229. Current velocity through a copper conductor is___________?
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A. of the order of a few ^.s/m

B. nearly 3 x 108 m/s

C. the same as propagation velocity of electric energy

D. independent of current strength

230. The chemical used in breather is_______________?
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A. asbestos fiber

B. sodium chloride

C. silica sand

D. silica gel
231. When secondary of a current transformer is open-circuited its iron core will be__________?
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A. hot because of heavy iron losses taking place in it due to high flux density

B. cool as there is no secondary current

C. none of above will happen

D. hot because primary will carry heavy current

232. Which of the following is the main advantage of an auto-transformer over a two winding transformer?
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A. Eddy losses are totally eliminated

B. Hysteresis losses are reduced

C. Saving in winding material

D. Copper losses are negligible

233. Silicon steel used in laminations mainly reduces___________?
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A. eddy current losses

B. hysteresis loss

C. copper losses

D. all of the above

234. If the percentage impedances of the two transformers working in parallel are different, then______________________?
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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
235. In a push pull converter, the filter capacitor can be obtained as____________?
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A. Cmin= ( 1 D ) V / ( Vr L f2 )

B. Cmin= ( 1 2 D ) V / 32 ( Vr L f2 )

C. Cmin= ( 1 2 D ) V / 42 ( Vr L f2 )

D. Cmin = V / ( Vr L f2 )

236. When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will___________?
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A. none of the above

B. remain constant

C. decrease

D. increase
237. In the case of direct current____________?
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A. magnitude and direction of current remains constant

B. magnitude of current remains constant

C. magnitude of current changes with time

D. magnitude and direction of current changes with time

238. A substance whose molecules consist of dissimilar atoms is called____________?
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A. super-conducto

B. semi-conductor

C. compound

D. insulator

239. The no load current in a transformer lags behind the applied voltage by an angle of about_____________?
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A. 180

B. 120?

C. 75

D. 90
240. Which of the following is not a routine test on transformers ?
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A. Polarity test

B. Impedance test

C. Core insulation voltage test

D. Radio interference test
241. 74. Sparking occurs when a load is switched off because the circuit has high_________?
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A. resistance

B. inductance

C. impedance

D. capacitance

242. The hot resistance of the bulbs filament is higher than its cold resistance because the temperature co-efficient of the filament is___________________?
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A. zero

B. positive

C. negative

D. about 2 ohms per degree

243. In the transformer the function of a conservator is to_______________?
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A. protect the transformer from damage when oil expends due to heating

B. none of the above

C. supply cooling oil to transformer in time of need

D. provide fresh air for cooling the transformer

244. A Buchholz relay can be installed on______________?
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A. auto-transformers

B. welding transformers

C. uchholz relay can be installed on

D. air-cooled transformers

E. oil cooled transformers
245. Spacers are provided between adjacent coils?
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A. to provide free passage to the cooling oil

B. to insulate the coils from each other

C. both A. and (b)

D. none of the above

246. The purpose of providing iron core in a step-up transformer is?
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A. to increase the magnitude of mutual flux

B. to provide coupling between primary and secondary

C. to provide all above features

D. to decrease the magnitude of mag-netizing current

247. Hysteresis loss in a transformer varies as CBmax = maximum flux density) ?
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A. Bmax1-83

B. Bmax1-6

C. B max

D. Bmax

248. Delta/star transformer works satisfactorily when______________?
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A. load is unbalanced only

B. load is balanced only

C. none of the above

D. on balanced as well as unbalanced loads
249. Which type of winding is used in 3 phase shell-type transformer?
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A. Cylindrical type

B. Circular type

C. Rectangular type

D. Sandwich type
250. 1 angstrom is equal to______________?
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A. 10-8 mm

B. 10?10 m

C. 10?6 cm

D. 10~14 m