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
5951. A synchronous motor can operate at____________?
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A. unity power factor only

B. leading power factor only

C. lagging, leading and unity power factors

D. lagging power factor only

5952. In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
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A. the motor is said to be fully loaded

B. the excitation is said to be hundred per cent

C. the excitation is said to be zero per cent

D. the torque generated is maximum

5953. Armature of a synchronous machine is____________?
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A. armature is associated with large power as compared to the field circuits

B. of difficulty of providing high voltage insulation on rotor

C. of reducing number of slip rings on the rotor

D. all of the above reasons
5954. The percentage slip in case of a synchronous motor is____________?
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A. 1%

B. zero

C. 0.50%

D. 100%

5955. The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?
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A. one hour

B. none of the above

C. one second

D. one minute

5956. A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?
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A. none of the above

B. go down

C. improve

D. remain same

5957. If load (or torque) angle of a 4-pole synchronous motor is 6 electrical, its value in mechanical degrees is__________?
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A. 6

B. 4

C. 2

D. 3
5958. In a synchronous motor, V-curves represent relation between____________?
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A. armature current and field current

B. field current and speed

C. field current and power factor

D. power factor and speed

5959. A synchronous machine with large air gap has______________?
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A. a higher synchronizing power which makes the machine less sensitive to load variations

B. a small value of inherent regulation

C. a higher value of stability limit

D. all of the above
5960. A rotory converter can also be run as a___________?
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A. induction motor

B. d.c. compound motor

C. d.c. series motor

D. d.c. shunt motor

E. synchronous motor
5961. The maximum speed variation in a 3-phase synchronous motor is____________?
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A. 10 per cent

B. 4 per cent

C. 6 per cent

D. 2. per cent

E. zero
5962. For V-curves for a synchronous motor the graph is drawn between:_______________?
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A. armature current and power factor

B. power factor and field current

C. terminal voltage and load factor

D. field current and armature current
5963. If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor__________?
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A. none of the above

B. become more

C. become less

D. remain constant

5964. An over-excited synchronous motor takes__________?
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A. leading current

B. lagging current

C. both A. and (b)

D. none of the above

5965. Slip-rings in a synchronous motor carry____________?
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A. no current

B. direct current

C. alternating current

D. all of the above

5966. Which of the following motors will be used in electric clocks?
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A. D.C. series motor

B. A.C. induction motor

C. A.C. synchronous motor

D. D.C. shunt motor

5967. Hunting in a synchronous motor cannot be due to___________?
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A. variable frequency

B. variable supply voltage

C. windage friction

D. variable load

5968. When the voltage applied to a synchronous motor is increased, which of the following will reduce?
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A. Stator flux

B. Pull in torque

C. Both A. and (b)

D. None of the above
5969. A synchronous motor can be made self starting by providing?
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A. damper winding on rotor poles

B. damper winding on stator as well as rotor poles

C. damper winding on stator

D. none of the above
5970. The operating speed of a synchronous motor can be changed to new fixed value by___________?
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A. changing the load

B. using brakes

C. changing frequency

D. changing the supply voltage

5971. A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have_____________?
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A. lagging power factor with over-excitation

B. leading power factor with over-excitation

C. leading power factor with under-excitation

D. no change of power factor

5972. The angle between the rotating stator flux and rotor poles is called _________ angle.
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A. torque

B. obtuse

C. power factor

D. synchronizing

5973. In a synchronous motor, damper windings are provided on____________?
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A. rotor shaft

B. none of the above

C. pole faces

D. stator frame

5974. An over excited synchronous motor is used for____________?
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A. variable speed loads

B. low torque loads

C. power factor corrections

D. fluctuating loads

5975. While starting a synchronous motor by induction motor action, field winding is usually_____________?
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A. kept open-circuited

B. connected to D.C. supply

C. short-circuited by low resistance

D. none of the above

5976. When V is the applied voltage, then the breakdown torque of a synchronous motor varies as_________?
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A. V

B. V2

C. 1/V

D. V312

5977. The shaft of synchronous motor is made of____________?
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A. alnico

B. mild steel

C. stainless steel

D. chrome steel

5978. When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
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A. augments it directly

B. none of the above

C. directly opposes it

D. cross-magnetises it

5979. A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?
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A. mechanical load on the rotor remains constant

B. synchronous motor has large airgap

C. stator supply is not required to produce magnetic field

D. synchronous motor has no slip

5980. The efficiency of a properly designed synchronous motor will usually fall in range___________?
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A. 99 to 99.5%

B. 75 to 80%

C. 85 to 95%

D. 60 to 70%

5981. The working of a synchronous motor is similar to_____________?
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A. turbine

B. transmission of mechanical power by shaft

C. distribution transformer

D. none of the above

E. gear train arrangement

5982. The armature current of the synchronous motor has higher values for_____________?
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A. high excitation only

B. low excitation only

C. both A. and (b)

D. none of the above

5983. The back e.m.f. in the stator of a synchronous motor depends on____________?
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A. flux density

B. none of the above

C. rotor speed

D. number of poles

E. rotor excitation
5984. A synchronous motor can be started by________?
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A. providing damper winding

B. D.C. compound motor

C. pony motor

D. any of the above
5985. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is_______________?
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A. under-loaded

B. supplied with unbalanced voltage

C. over-loaded

D. none of the above

5986. Synchronous motor always runs at______________?
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A. less than synchronous speed

B. none of the above

C. the synchronous speed

D. more than synchronous speed

5987. Which of the following methods is used to start a synchronous motor?
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A. Damper winding

B. Star-delta starter

C. Resistance starter in the armature circuit

D. Damper winding in conjunction with star-delta starter
5988. An important advantage of a synchronous motor over wound round induction motor is that
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A. none of the above

B. its speed may be controlled more easily

C. its speed is independent of supply frequency

D. its power factor may be varied at will
5989. The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as_____________?
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A. slip torque

B. pull-out torque

C. synchronising torque

D. breaking torque

5990. If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
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A. will become more

B. will remain unchanged

C. none of the above.

D. will become less
5991. The net armature voltage of a synchronous motor is equal to the_______________?
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A. arithmetic sum of Eb and V

B. arithmetic difference of Eb and V

C. vector sum of Eb and V

D. vector difference of Eh and V
5992. Power factor of a synchronous motor is unity when_____________?
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A. the armature current is minimum

B. none of the above

C. the armature current is maximum

D. the armature current is zero

5993. If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
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A. the motor stops

B. it continues to run at the same speed

C. it runs at a very high speed

D. it runs at a slower speed

5994. In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be____________?
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A. 750 r.p.m.

B. 3000 r.p.m.

C. none of the above

D. 1500 r.p.m.
5995. A synchronous motor working at leading power factor can be used as____________?
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A. noise generator

B. voltage booster

C. mechanical synchronizer

D. phase advancer
5996. A synchronous motor develops maximum power when load angle is____________?
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A. 90

B. 45

C. 60

D. 120

5997. If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to____________?
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A. increase in both armature current and power factor angle

B. increase in back e.m.f. but decrease in armature current

C. increase in both armature current and power factor which is lagging

D. increase in torque angle but decrease in back e.m.f.

5998. Synchronsizing power of a synchronous machine is_____________?
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A. none of the above

B. direcly proportional to the synchronous reactance

C. equal to the synchronous reactance

D. inversely proportional to the synchronous reactance
5999. Stability of a synchronous machine:
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A. remains unaffected with increase in excitation

B. decreases with increase in its excitation

C. any of the above

D. increases with increase in its excitation
6000. In which of the following motors the stator and rotor magnetic field rotate at the same speed?
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A. Universal motor

B. Induction motor

C. Reluctance motor

D. Synchronous motor