electrical engineering Mcqs
1201. For power factor correction, synchronous motors operate at____________?
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A. normal load with minimum excitation

B. no-load and under-excited fields

C. normal load with zero excitation

D. no-load and greatly over-excited fields
1202. 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. synchronous motor has large airgap

B. synchronous motor has no slip

C. mechanical load on the rotor remains constant

D. stator supply is not required to produce magnetic field
1204. Annual depreciation of the plant it proportional to the earning capacity of the plant vide
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A. reducing balances depreciation

B. none of the above

C. sinking fund depreciation

D. straight line depreciation

1205. The power demand can be estimated approximately by____________?
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A. Statistical method

B. Load survey method

C. Economic parameters

D. Mathematical method

1206. In a synchronous motor, the breakdown torque is__________?
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A. directly proportional to applied voltage

B. none of the above

C. directly proportional to the square of the applied voltage

D. inversely proportional to applied voltage

1207. The effect of electric shock on human body depends on which of the following?
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A. current

B. voltage

C. all of the above

D. duration of contact

1208. A synchronous machine with large air gap has______________?
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A. a small value of inherent regulation

B. a higher value of stability limit

C. all of the above

D. a higher synchronizing power which makes the machine less sensitive to load variations

1210. The form factor is the ratio of_______?
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A. peak value to r.m.s. value

B. r.m.s. value to average value

C. none of the above

D. average value to r.m.s. value

1211. The operating speed of a synchronous motor can be changed to new fixed value by___________?
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A. changing the supply voltage

B. changing frequency

C. using brakes

D. changing the load

1212. A low utilization factor for a plant indicates that
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A. plant is used for stand by purpose only

B. plant is used for peak load as well as base load

C. plant is under maintenance

D. plant is used for base load only

1215. 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 torque generated is maximum

C. the excitation is said to be hundred per cent

D. the excitation is said to be zero per cent

1216. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor___________?
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A. decreases to half the original value

B. remains same as the original value

C. tends to becomes zero

D. increases to two times the original value
1217. Load shedding is possible through which of the following?
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A. Any of the above

B. Voltage reduction

C. Frequency reduction

D. Switching of the loads

1219. Stability of a synchronous machine:
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A. increases with increase in its excitation

B. decreases with increase in its excitation

C. remains unaffected with increase in excitation

D. any of the above

1220. Which of the following is the disadvantage of static capacitor for power factor improvement?
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A. All of the above

B. Easily damaged by high voltage

C. Cannot be repaired

D. Short service life

1222. ___________ is invariably used as base load plant.
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A. Pumped storage plant

B. Nuclear power plant

C. Diesel engine plant

D. Gas turbine plant

1223. A non-linear network does not satisfy__________?
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A. superposition condition

B. homogeneity condition

C. both homogeneity as well as superposition condition

D. homogeneity, superposition and associative condition

1224. Maximum demand on a power plant is_________________?
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A. the greatest of all short time interval averaged demand during a period

B. instantaneous maximum value of kVA supplied during a period

C. both A. or B.

D. none of the above

1225. The period of a wave is___________?
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A. the same as frequency

B. time required to complete one cycle

C. expressed in amperes

D. none of the above

1226. If a shunt motor is started with its field winding open then___________?
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A. None of these

B. It will rotate at dangerously high speed

C. It will rotate at the same speed as that with its field winding closed

D. It will rotate at less speed as that with its field winding closed

1228. A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
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A. Eb (back e.m.f.) becomes less than V (applied voltage)

B. Er (net resultant voltage) in armature is increased

C. power factor is decreased

D. speed of the motor is reduced

E. none of the above

1229. In Hopkinson demand rate or two part tariff the demand rate or fixed charges are__________?
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A. dependent upon the energy consumed

B. dependent upon the maximum demand of the consumer

C. both A and B

D. neither A nor B

1230. Kirchhoff s voltage law applies to circuits with____________?
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A. linear elements only

B. nonlinear elements only

C. linear, non-linear, active and passive elements

D. linear, non-linear, active, passive, time varying as wells as time-in-variant elements
1231. For similar carrier and modulating signals, the line current used in CSI is_____________?
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A. Identical to line current in VSI

B. Identical to phase voltage in VSI

C. Identical to phase voltage in CSI

D. Identical to line voltage in a VSI
1232. __________ will be least affected due to charge in supply voltage frequency.
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A. Electric clock

B. Mixer grinder

C. Room heater

D. Ceiling fan

1233. If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then_____________?
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A. the back e.m.f. will be more than the supply voltage

B. the stator current will be very small

C. none of the above

D. the stator current will be zero

E. the stator current will be very high

1234. A load curve indicates___________?
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A. average kWh (kW) energy consumption during the period

B. either of the above

C. average power used during the period

D. none of the above

1235. Air will not be the working substance in which of the following?
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A. Petrol engine

B. Diesel engine

C. Closed cycle gas turbine

D. Open cycle gas turbine

1236. Which of the following is not a source of power?
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A. Solar cell

B. Thermocouple

C. Photoelectric cell

D. Photovoltaic cell

1237. Annual depreciation as per straight line method, is calculated by__________?
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A. none of the above

B. the capital cost divided by number of year of life

C. the capital cost minus the salvage value, is divided by the number of years of life

D. increasing a uniform sum of money per annum at stipulated rate of interest

1239. Under which of the following conditions hunting of synchronous motor is likely to occur?
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A. Periodic variation of load

B. Over-excitation

C. Small and constant load

D. Over-loading for long periods

1241. Power electronics essentially deals with control of a.c. power at____________?
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A. Frequencies above 1000 kHz

B. Frequencies above 20 kHz

C. Frequencies less than 10 Hz

D. 50 Hz frequency
1243. Which of the following is the disadvantage of a synchronous condenser?
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A. Continuous losses in motor

B. Noise

C. High maintenance cost

D. All of the above
1244. Kirchhoffs voltage law is related to_____________?
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A. junction currents

B. battery e.m.fs.

C. IR drops

D. both B. and C.

E. none of the above

1247. In a synchronous motor, the magnitude of stator back e.m.f. & depends on_______________?
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A. d.c. excitation only

B. speed of the motor

C. load on the motor

D. both the speed and rotor flux

1248. Which of the following methods is used to start a synchronous motor?
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A. Resistance starter in the armature circuit

B. Damper winding

C. Star-delta starter

D. Damper winding in conjunction with star-delta starter
1250. The knowledge of diversity factor helps in determining__________?
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A. average load

B. peak load

C. kWh generated

D. plant capacity