MRPL electrical 21-Feb-2021 question paper with solution

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## All Questions and Answer of MRPL 21-feb-2021

1. Reheat factors in steam turbine depends on

(A) Exit pressure only

(B) Stage efficiency only

(C) Initial pressure and temperature only

(D) All of these

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Ans- D

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2. Francis turbine is usually used for

(A) Low head installation up to 30m

(B) Medium head installation from 30m to 180m.

(C) High installation above 180m.

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3. Load factor of power station is defined as

(B) Average load * maximum demand

(D) None of the above

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Ans -c

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4. Most efficient plants are normally used as

(C) Either (A) or (B)

(D) None of the above

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5. For the same maximum demand if load factors are decreased, the cost of generation will

(A) Remain unchanged

(B) Decrease

(C) Increase

(D) None of these

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6. For cooling of large size generators hydrogen is used because

(A) It is light

(B) It offers reduced fire risk

(C) It has high thermal conductivity

(D) All of these

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7. Which of the following is not a source of power?

(A) Thermocouple

(B) Solar cell

(C) Photovoltaic cell

(D) Photo electric cell

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8. Bundle conductors in a transmission line

(C) No effect

(D) None of these

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9. When a pumped storage power plant is operated in conjunction with a steam power plant

(A) The operating cost of the steam plant becomesoptimum

(B) Load factor of the steam plant is increased

(C) Chances of the tripping of the system decrease because of the use of two heterogenous types of plants

(D) Operation of the storage plant in the pumping mode during the low-load period improves the steam-plant stability

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10. A negative sequence relay is commonly used to protect

(A) An alternator

(B) A transformer

(C) A transmission line

(D) A bus bar

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11. A 250V lamp has total flux of 1500 lumens and takes a current of 0.4A. The no. of lumen per watt are

(A) 8

(B) 10

(C) 13

(D) 15

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12. The vapour discharge tube used for  domestic lighting has

(A) No filament

(B) One filament

(C) Two filaments

(D) Tree filaments

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13. In sodium vapour lamp the function of the leak transformer is

(A) To stabilize the arc

(B) To reduce supply voltage

(C) Both (A) and (B)

(D) None of these

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14. Which part of a motor needs maximum attention for maintenance

(A) Frame

(B) Bearing

(C) Stator winding

(D) Rotor winding

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15. Heavy duty cranes are used in

(A) Ore handling plants

(B) Steel plants

(C) Heavy engineering workshops

(D) All of the above

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16. Which of the following is the advantages of electric breaking

(A) It avoids wear of track

(B) Motor continues to remain loaded during braking

(C) It is instantaneous

(D) More heat is generated during breaking

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17. Reluctance motor is a

(A) Variable torque motor

(B) Low torque variable speed motor

(C) Self-starting type synchronous motor

(D) Low noise, slow speed motor

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18. Battery operated scooter for breaking uses

(A) Plugging

(B) Mechanical breaking

(C) Regenerative braking

(D) Rheostatic braking

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19. To obtain n type semi-conductor the impurity added to

a pure semiconductor is

(A) Trivalent

(B) Tetravalent

(C) Pentavalent

(D) None of these

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20. A Zener diode has a

(B) Negative resistance

(C) High amplification

(D) Sharp breakdown voltage at low reverse voltage

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21. Potential barrier at a p-n junction is established due to the changes on either side of the junction. Those changes are

(A) Majority carriers

(B) Minority carriers

(C) Both (A) and (B)

(D) Donor and acceptor ions

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22. A transistor when connected in C.E mode has

(A) A low input resistance and a low output resistance

(B) A high input resistance and a high output resistance

(C) A high input resistance and a low output resistance

(D) A medium input resistance and a high output resistance

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23. The output power of a power amplifier is several times its input power. It is so because

(A) Step-up transformer is used at the output

(B) Transistor acts as a power source

(C) Power amplifier introduces positive feedback

(D) Power amplifier converts a part of input dc power into an ac output power

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24. TTL circuits with active pull up are preferred because

of their suitability for

(A) Wired AND operation

(B) Bus operated system

(C) Wired logic operation

(D) Reasonable dissipation and speed of operation

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25. The simplified form of logic function Y= (A.B).(A B)is:

(A) A+B

(B) AB

(C) A + B

(D)A•B+A•B

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26. The comparators required in a 3-bit comparators type ADC is

(A) 2

(B) 3

(C) 7

(D) 8

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27. The Boolean function Y=AB +CD is to be realized using only 2-input NAND gates. The minimum no. of gates required is

(A) 2

(B) 3

(C) 4

(D) 5

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28. The pulse width modulated inverter for an ac motor is fed from which one of the following?

(A) Controlled rectifiers

(B) Uncontrolled rectifier

(C) Ac regulator

(D) Cycloconverter

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29. Which one of the following devices should be used as switch in a low power switched mode power supply (SMPS)?

(A) GTO

(C) TRIAC

(B) MOSFET

(D) THYRISTOR

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30. A cyclo converter fed induction motor drive is most suitable for which one of the following?

(A) Compressor drive

(B) Machine tool

(C) Paper will drive

(D) Cement will drive

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31. A buck regulator has an input voltage of 12V and the required output voltage is 5V. What is the duty cycle of the regulator?

(A) 5/12

(B) 12/5

(C) 5/2

(D) 6

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32. In an LC series circuit connected to a DC supply of E volts via thyristor. When it turns off the voltage that appears across the thyristors is

(A) +E

(C) -E

(B) +2E

(D) -2E

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33. In a 3-phase semi-converter, for firing angle less than or equal to 60° freewheeling diode conducts for

(A) 90°

(C) 30°

(B) 60°

(D) 0°

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34. Which type of connection is employed for current transformers for the protection of star-delta connected 3-phase transformer

(A) delta-delta

(B) star-star

(C) star-delta

(D) delta-star

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35. The corona loss on a particular system at 50Hz is 1KW/KM per phase. What is corona loss at 60z in KW/KM per phase?

(A) 0.83

(B) 1.0

(C) 1.13

(D) 1.2

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36. If the number of stator slots be equal to the number of rotor slots, the machine would refuse to start, this is known as

(A) Cogging

(B) Crawling

(C) Either of the above

(D) None of the above

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37. A large value of short-circuit indicator

(A) A poor power factor

(B) A good power factor

(C) Zero power factor

(D) None of the above

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38. The flash point of transformers oil should be higher than

(A) 40°C

(C) 80°C

(B) 60°C

(D) 104°C

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39. A man has three resistance each of value 1/3 Q. What is the minimum resistance he can obtain by combining them?

(A) 1

(C) 1/6 0

(B) 3 0

(D) 1/9

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40. A battery is made by combination of 6 cells in series, each capable to deliver 4 amperes at 2V. how much voltage and current can it deliver?

(A) 12V and 24A

(B) 2V and 24A

(C) 12V and 4A

(D) 2V and 4A

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