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
301. With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals_____________?
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A. 20 W

B. 10 W

C. 60 W

D. 40 W

302. Star/star transformers work satisfactorily when________________?
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A. load is balanced only

B. none of the above

C. load is unbalanced only

D. on balanced as well as unbalanced loads

303. Power transformers are designed to have maximum efficiency at___________?
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A. 50% full load

B. no load

C. nearly full load

D. 70% full load

304. The leakage flux in a transformer depends upon______________?
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A. load current, voltage and frequency

B. load current

C. load current and voltage

D. load current, voltage, frequency and power factor

305. A step down choppers can be used in___________?
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A. All of these

B. Machine tools

C. Electric traction

D. Electric vehicles

306. Electric pressure is also called________?
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A. power

B. voltage

C. resistance

D. energy

307. Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ___________?
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A. 3/2 Q

B. 6 Q

C. 8/3 Q

D. 4 Q
308. In a circuit a 33 Q resistor carries a current of 2 A. The voltage across the resistor is
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A. 132 V

B. 80 V

C. 66 v

D. 33 V

309. With rise in temperature the resistance of pure metals______________?
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A. remains constant

B. decreases

C. increases

D. first increases and then decreases

310. Out of the following which is not a poor conductor__________?
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A. Copper

B. Cast iron

C. Carbon

D. Tungsten

311. If energy is taken from the AC side of the inverter and sends it back into the DC side, then it is known as___________?
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A. None of these

B. Regenerative mode operation

C. Motoring mode operation

D. Braking mode operation

312. In a flyback converter, the inductor of the buck-boost converter has been replaced by a_____________?
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A. Flyback transformer

B. Flyback transistor

C. Flyback resistor

D. Flyback capacitor

313. If the efficiency of a machine is to be high, what should be low __________?
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A. True component of power

B. Losses

C. Ratio of output to input

D. kWh consumed

E. Input power

314. The thickness of laminations used in a transformer is usually____________?
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A. 14 mm to 15 mm

B. 4 mm to 5 mm

C. 25 mm to 40 mm

D. 0.4 mm to 0.5 mm
315. Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes__________?
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A. unchanged

B. 9 times

C. 1/9 times

D. 3 times

316. In the transformer following winding has got more cross-sectional area______________?
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A. Low voltage winding

B. Primary winding

C. High voltage winding

D. Secondary winding

317. Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 25 Q. If the same four wires are connected is series the effective resistance will be________?
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A. 300 ?

B. 200 ?

C. 400 ?

D. 100 ?

318. Efficiency of a power transformer is of the order of________________?
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A. 100 per cent

B. 98 per cent

C. 25 per cent

D. 50 per cent

319. The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is___________?
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A. Sine wave

B. Square wave

C. Saw tooth wave

D. Trapezoidal wave

320. Iron loss of a transformer can be measured by____________?
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A. frequency meter

B. any type of wattmeter

C. low power factor wattmeter

D. unity power factor wattmeter

321. The core used in high frequency transformer is usually___________?
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A. cost iron core

B. copper core

C. mild steel core

D. air core
322. Two transformers operating in parallel will share the load depending upon their____________?
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A. efficiencies

B. leakage reactance

C. per unit impedance

D. ratings

323. A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms respectively. The current in each branch is_____________?
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A. 4.6 A, 6.9 A

B. 4.6 A, 9.6 A

C. 6.4 A, 6.9 A

D. 6.4 A, 9.6 A
324. When one leg of parallel circuit is opened out the total current will______________?
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A. increase

B. decrease

C. reduce

D. become zero

325. Insulating materials have the function of______________?
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A. storing very high currents

B. preventing an open circuit between the voltage source and the load

C. conducting very large currents

D. preventing a short circuit between conducting wires
326. Resistance of a material always decreases if___________?
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A. number of free electrons available become more

B. none of the above is correct

C. temperature of material is increased

D. temperature of material is decreased

327. The main reason for generation of harmonics in a transformer could be_______________?
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A. fluctuating load

B. saturation of core

C. poor insulation

D. mechanical vibrations

328. A transformer cannot raise or lower the voltage of a D.C. supply because_______________?
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A. there is no need to change the D.C. voltage

B. none of the above

C. Faradays laws of electromagnetic induction are not valid since the rate of change of flux is zero

D. a D.C. circuit has more losses

329. The resistance of a few meters of wire conductor in closed electrical circuit is____________?
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A. very high

B. low

C. high

D. practically zero
330. Which winding in a transformer has more number of turns ?
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A. Primary winding

B. Secondary winding

C. High voltage winding

D. Low voltage winding

331. An SCR can be used___________?
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A. All of these

B. for power control

C. as static conductor

D. for speed control of dc shunt motor

332. In a transformer the tappings are generally provided on_____________?
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A. secondary side

B. high voltage side

C. primary side

D. low voltage side

333. A carrier based PWM technique in CSI is composed of____________?
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A. A switching and shorting pulse combination

B. A shorting pulse distributor

C. All of these

D. A switching pulse generator and a shorting pulse generator

334. A light bulb draws 300 mA when the voltage across it is 240 V. The resistance of the light bulb is___________?
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A. 400 Q

B. 600 Q

C. 800 Q

D. 1000 Q

335. An ideal diode is___________?
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A. Only (a) and (c)

B. Bidirectional

C. Fixed voltage polarity

D. Unidirectional

336. In a transformer the energy is conveyed from primary to secondary_________?
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A. none of the above

B. through cooling coil

C. through air

D. by the flux
337. A transformer can have zero voltage regulation at______________?
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A. zero power factor

B. unity power factor

C. leading power factor

D. lagging power factor

338. In a transformer the resistance between its primary and secondary is____________?
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A. 1000 ohms

B. 1 ohm

C. infinite

D. zero

339. The permissible flux density in case of cold rolled grain oriented steel is around__________?
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A. 3.7 Wb/m2

B. 4.7 Wb/m2

C. 2.7 Wb/m2

D. 1.7 Wb/m2
340. If/, R and t are the current, resistance and time respectively, then according to Joules law heat produced will be proportional to_______________?
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A. I2Rt

B. I2R2t*

C. I2Rf

D. I2R2t

341. In square wave operation mode of 3 phase VSI, the VSI
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A. Cannot control the load voltage

B. Cannot control the load voltage except by means of dc link voltage

C. Can control the load voltage

D. Cannot control the load voltage except by means of dc link current

342. Harmonics in 3 phase inverters can be reduced by using___________?
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A. Passive filter

B. Active filter

C. Both passive and active filters

D. None of these

343. A transformer oil must be free from________________?
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A. moisture

B. gases

C. sludge

D. odour

344. In a lamp load when more than one lamp are switched on the total resistance of the load_____________?
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A. remains same

B. increases

C. none of the above

D. decreases
345. The size of poxvirus is_______________?
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A. 20 nm

B. 200 nm

C. 250 nm

D. 300 nm
346. A crowbar is a circuit which is used to protect a_____________?
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A. voltage sensitive load from excessive ac power supply output voltages

B. voltage sensitive load from excessive dc power supply output voltages

C. current sensitive load from excessive dc power supply output voltages

D. current sensitive load from excessive ac power supply output voltages

347. Transformer utilization factor is a measure of the merit of a rectifier circuit. It is the ratio of_______________?
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A. AC input power to the transformer volt amp rating required by primary

B. AC input power to the transformer volt amp rating required by secondary

C. DC output power to the transformer volt amp rating required by secondary

D. DC output power to the transformer volt amp rating required by primary

348. Which of the following is not a part of transformer installation ?
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A. Buchholz relay

B. Exciter

C. Conservator

D. Breather

349. Ohms law is not applicable to__________?
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A. D. C. circuits

B. small resistors

C. semi-conductors

D. high currents

350. When a given transformer is run at its rated voltage but reduced frequency, its____________?
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A. iron losses are reduced

B. core flux density is reduced

C. flux density remains unaffected

D. core flux density is increased