2021 Model Question Paper Of Electrical Engineering with PDF

MCQ QUESTION [ TRANSFORMER & INDUCTION MOTOR]

This MCQ set is practice purpose for competitive exams . This MCQ set follow upcomming Trends for Diploma and bachelor degree.This MCQ question only for Transformer and  Induction Motor. This MCQ set not cover all the part of Transformer and Induction Motor

TRANSFORMER

1. Why is the open circuit test or No Load test of the transformer done to get what?

 A) Total loss

 B) copper loss

 C) iron loss

 D) friction loss

2. If primary current increases what will be the effect of leakage reactance?

 A) increase

 B) decrease

 C) same 

 D) None of the above

3. What is the percentage of total flux is leakage flux?

 A) 4 percent

 B) 5 percent

 C) 5.5 percent

 D) 6 percent

4. At Maximum Efficiency of transformer Iron loss=

 A) Copper loss

 B) total loss

 C) eddy current loss

 D) None of the above

5. No-load power factor cos Φ0=

 A) Iw/I0

 B) Im/I0

 C) I0/Iw

 D) none of the above

6. If a Transformer input voltage 250 v and no-load current is 4.3 A at 0.5 (lagging)

 A) 500 w

 B) 537.5 w

 C) 322 w

 D) 516 w

7. What percentage of total loss is Copper loss of Transformer

 A) 95 percent

 B) 85 percent

 C) 80 percent

 D) 71 percent

8. If current increases in Transformer which loss will increases-

 A) friction loss

 B) Iron loss

 C) eddy current loss

 D) Copper loss

9. If flux density of Transformer is constant which loss remain constant

 A) Hysteresis loss

 B) Eddy current loss

 C) Hysteresis and Eddy current loss

 D) none of the above

10. Maximum efficiency of large rated Transformer

 A) 60 percent

 B) 55 percent

 C) 85 percent

 D) 95 percent

11. Which two things are similar are both primary and secondary winding 

Of the Transformer-

 A) current & voltage

 B) resistance & leakage reactance

 C) ampere-turns & voltage/turn

 D) None of the above

12. 

13. If Input voltage of the Transformer is 250v and primary impedance Is 1.2 kohm and secondary impedance is 2 ohm ,the truns ratio is ....

 A) 25:1

 B) 200:1

 C) 60:1

 D) 50:1

14. Primary and secondary linked each other of Transformer

 A) Electrical link

 B) magnetical link

 C) mechanical link

 D) None of the above

INDUCTION MOTOR

15. What is the power of maximum flux density in Hysteresis loss and Eddy current loss-

 A) 1.6 & 2

 B) 2 & 1.6

 C)  2& 1

 D) None of the above

16. When Rotor resistance/phase is equal to standstill rotor reactance/phase-

 A) At Starting Torque

 B) At running Torque

 C) A&B both

 D) None of the above

17. When we see rotor power factor 0.707 lag

 A) Starting Torque

 B) Running Torque

 C) A&B both

 D) None of the above

18. If 4 pole 50 hz 3 phase induction motor synchronous speed1455 RPM and Rotor speed 1355 RPM what is the rotor frequency?

 A) 3.43 hz

 B) 1.53 hz

 C) 2.95 hz

 D) 4 hz

19. If 3 phase induction motor Load increases what will be the effect on power factor

 A) increase

 B) decrease

 C) same

 D) none of the above

20. What is the similarity we follow between standstill induction motor and Transformer?

 A) short-circuited secondary

 B) open-circuited secondary

 C) variable resistance

 D) None of the above

21. DC shunt motor Torque characteristics similar with

 A) DC series motor

 B) synchronous motor

 C) 3-phase induction motor

 D) DC differential compounded motor

22. If airgap of 3 phase induction motor is increase what parameter is Effected

 A) speed reduce

 B) Decrease power factor

 C) improve efficiency

 D) speed increasing

23.  If induction motor Rotor resistance of 0.008 ohm/phase

 increase to 0.016ohm/phase, what is the effect on maximum torque ?

 A) remain unchanged

 B) increase by 100 percent

 C) decrease by half

 D) increase by 200 percent

24. Cause of 3 phase induction motor does not accelerate upto full acclaration

 A) 7th Harmonic

 B) 5th Harmonic

 C) 3rd Harmonic

 D) None of the above

25. If slip is 2% and 3 phase induction motor output power is 20 kw , what is the copper loss

 A)  408. 16 w

 B)  400.2 w

 C) 395 w

 D) 416.23 w

26. Choose the correct answer

 A) Rotor rotation is equal to the direction of stator flux

 B) Rotor rotation is opposite of the direction of stator flux

 C) insufficient data

 D) None of the above

27. Outer cage of Double cage induction motor 

 A) inductance is high

 B) inductance is low

 C) resistance is low

 D) resistance is high

28.  Which starter use for extra high HP Induction motor

 A) DOL

 B) Star-delta 

 C) Autotransformer

 D) None of the above

29. Which Speed Control method is use in Squirrel cage induction motor

 A) Pole change, voltage control, by VFD

 B) pole change ,rheostatic control

 C) cascade control

 D) None of the above

30. During starting power factor will be

 A) lagging

 B) leading

 C) unity

 D) None of the above

 ------------------------------------------------

Answer

1) ... Answer is C)

W=iron loss .'. here W is no load input power"

2)... Answer is B)

L=NΦ/I . .'.X=2πfL so if"

3)... Answer is B)

5 percent flux is not linked with secondary

4)... Answer is A)

Iron loss = Copper loss

5)... Answer is A)

Iw=I0 cos =I0 cos I0=√(Im² +Iw²) Cos Φ0 =Iw/I0

6)... Answer is B)

7)... Answer is B)

8)... Answer is D)

P=I²R I increase P also increase

9)... Answer is C)

Flux density of Transformer is remain constant always and Hysteresis loss and eddy current loss voltage depending loss so if flux density constant voltage also constant..

10)... Answer is D)

11)... Answer is D)

12)... Answer is A)

13)... Answer is A)

k²= primary impedance/secondary impedance

14)... Answer is B)

15)... Answer is A)

16)... Answer is A)

17)... Answer is A)

18)... Answer is A)

s=((Ns-Nr)/Ns)=((1455-1355)/1455)=0.06.'. f'=sf,f'=0.06×50= 3.43 hz where f' is rotor frequency

Show Answer

19)... Answer is B)

If load increase speed also decrease so slip is increasing that slip increase the Rotor frequency if frequency is increasing then z is increased and power factor decrease.

20)... Answer is A)

21)... Answer is C)

 

22)... Answer is B)

23)... Answer is B)

24)Answer is A)

 25)... Answer is A)

Rotor Copper loss/Rotor output=a/1-a=0.02/(1-0.02)=0.02/0.98 Rotor Copper loss = 0.02/0.96× Rotor output power (20×10³)=408.16 w

26)... Answer is A)

27)... Answer is D)

28)... Answer is C)

29)... Answer is A)

30)... Answer is A)

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