MCQ in Transformers Part 1 | REE Board Exam

(Last Updated On: August 6, 2020)

MCQ in Transformers Part 1 | REE Board Exam

This is the Multiple Choice Questions Part 1 of the Series in Transformers as one of the Electrical Engineering topic. In Preparation for the REE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electrical Engineering field, Electrical Engineering Books, Journals and other Electrical Engineering References.

Start Practice Exam Test Questions Part 1 of the Series

Choose the letter of the best answer in each questions.

1. REE Board Exam April 1997

A single-phase transformer is rated 4,160-V primary and 250-V secondary. It has 1,500 turns in the primary and voltage regulation of 8%. What should be the number of turns in the secondary winding?

A. 88 turns

B. 92 turns

C. 90 turns

D. 86 turns

View Answer:

Answer: Option C

Solution:

2. EE Board Exam April 1991

A certain transformer has a ratio of 8 is to 1. The primary winding resistance is 0.00283 Ω per turn and has 1,155 more turns than the secondary winding. If the copper loss in the primary is 20% less than the secondary, find the resistance of the secondary winding.

A. 0.073 ohm

B. 0.090 ohm

C. 0.068 ohm

D. 0.084 ohm

View Answer:

Answer: Option A

Solution:

3. EE Board Exam October 1991

A 10-kVA; 2,400/240 V single-phase transformer has the following resistances and leakage reactances. Find the primary voltage required to produce 240-V at the secondary terminals at fullload when the load power factor is 0.8 lagging.

r1 = 3 ohms                                    r2 = 0.03 ohm

x1 = 15 ohms                                  x2 = 0.15 ohm

A. 2,450 volts

B. 2,575 volts

C. 2,496 volts

D. 2,632 volts

View Answer:

Answer: Option C

Solution:

4. EE Board Exam April 1983

A single-phase transformer rated 75 kVA, 8000 volts primary and 240 volts secondary is given the short circuit test. With the secondary terminals short circuited, 440 volts (60 Hz) is impressed on the primary, which then draws rated current and 1125 watts. Solve for the percentage impedance of the transformer.

A. 5.29%

B. 4.93%

C. 5.50%

D. 5.13%

View Answer:

Answer: Option C

Solution:

5. EE Board Exam April 1993

A short circuit test was performed upon a 10-kVA, 2300/230 volt transformer with the following results: Esc = 137 volts; Psc = 192 W; Isc = 4.34 A. Calculate in primary terms the reactance of the transformer.

A. 31.56 ohms

B. 29.88 ohms

C. 10.19 ohms

D. 12.45 ohms

View Answer:

Answer: Option B

Solution:

6. EE Board Exam October 1984

A single-phase, 25 kVA, 4800/240 volt transformer was given the short circuit test. With the secondary terminals short-circuited, 93.75 volts was applied on the primary so that the ammeter reads rated current and the wattmeter reads 162.74 watts, all on the primary side. Solve for the percentage resistance of the transformer

A. 1.95%

B. 3.39%

C. 3.02%

D. 2.23%

View Answer:

Answer: Option B

Solution:

7. EE Board Exam April 1990

The following data were obtained when a short circuit test was performed upon a 100 kVA, 2400/240 volts distribution transformer: Esc = 72 volts; Isc = 41.6 A; Psc = 1,180 W. All instruments are on the high side during the short circuit test. Calculate the equivalent resistance and reactance of the transformer.

A. 0.682 ohm, 1.59 ohms

B. 0.682 ohm, 1.73 ohms

C. 0.752 ohm, 1.73 ohms

D. 0.752 ohm, 1.59 ohms

View Answer:

Answer: Option A

Solution:

8. REE Board Exam March 1998

A 13.8 kV/480 V, 10 MVA three-phase transformer has 5% impedance. What is the impedance in ohms referred to the primary?

A. 0.952 ohm

B. 0.03 ohm

C. 5.125 ohms

D. 9.01 ohms

View Answer:

Answer: Option A

Solution:

9. EE Board Exam April 1990 B.

The following data were obtained when a short circuit test was performed upon a 100 kVA, 2400/240 volts distribution transformer: Esc = 72 volts; Isc = 41.6 A; Psc = 1,180 W. All instruments are on the high side during the short circuit test. Calculate the percent regulation at a power factor of 0.75 lagging.

A. 2.54%

B. 2.86%

C. 2.62%

D. 2.71%

View Answer:

Answer: Option D

Solution:

10. EE Board Exam October 1992

A 200-kVA transformer with impedance of 5% and the power factor of the load is 85%. The primary voltage is 6,000 volts while the copper loss is 5 kW. Find the percentage regulation.

A. 5.03%

B. 5.21%

C. 4.43%

D. 4.03%

View Answer:

Answer: Option C

Solution:

11. EE Board Exam April 1993

A short circuit test was performed upon a 10-kVA, 2300/230 volt transformer with the following results: Esc = 137 volts; Psc = 192 W; Isc = 4.34 A. Calculate the percent regulation at a lagging power factor of 0.707.

A. 5.28%

B. 5.55%

C. 5.37%

D. 5.72%

View Answer:

Answer: Option C

Solution:

12. EE Board Exam October 1992

In a 440 V, 50 c/s transformer, the total iron loss is 2500 W. When the supplied p.d. is 220 V at 25 c/s, the corresponding loss is 850 W. Calculate the eddy current loss at normal frequency and p.d.

A. 2337 W

B. 2165 W

C. 2010 W

D. 2216 W

View Answer:

Answer: Option B

Solution:

13. EE Board Exam April 1990

A 50 kVA, 2300/230 volts, 60 cycle transformer is tested in the laboratory so that its characteristics maybe determined. The standard test requires an open circuit test and short circuit test.

Open Circuit Test:

I = 6.5 A     E = 230 V     P = 187 W

Short Circuit Test

I = 21.7 A    E = 115 V      P = 570 W

Determine the efficiency of the transformer at half load, unity pf.

A. 97.55%

B. 98.70%

C. 98.45%

D. 97.80%

View Answer:

Answer: Option B

Solution:

14. EE Board Exam April 1992

Given that the full load copper losses are exactly twice the iron losses in a 50 kVA transformer, and that the quarter load efficiency is 96.5%, calculate the full load efficiency at unity power factor.

A. 97.48%

B. 98.12%

C. 97.64%

D. 96.25%

View Answer:

Answer: Option C

Solution:

15. EE Board Exam April 1995

The core loss of a 5 kVA single –phase transformer with normal voltage applied to the primary is 75 watts. The maximum efficiency occurs at 60% of full-load kVA. What is the fullload efficiency of the transformer at 0.80 power factor?

A. 95.16%

B. 89.52%

C. 93.38%

D. 91.36%

View Answer:

Answer: Option C

Solution:

16. EE Board Exam October 1980, October 1982

A 25-kVA distribution transformer operates at 120% load, 0.3 pf lagging for 1 hour; art full-load, 0.9 lagging pf for 3 hours; 50% load at unity pf for 8 hours; and 10% load at 0.8 leading pf for the rest of the day. If core loss is 150 watts and full load copper loss is 500 W, what is the all-day efficiency of the transformer?

A. 94.23%

B. 92.86%

C. 97.14%

D. 96.68%

View Answer:

Answer: Option D

Solution:

17. EE Board Exam October 1990

Find the all-day efficiency of a transformer having maximum efficiency of 98% at 15-kVA at unity power factor and loaded as follows:

12 hours 2-kW at 0.5 pf lagging

6 hours 12-kW at 0.8 pf lagging

6 hours at no load

A. 95.3%

B. 91.7%

C. 94.6%

D. 93.3%

View Answer:

Answer: Option A

Solution:

18. EE Board Exam October 1991

A 30-kVA, 2,400/240 volts, 60-Hz transformer has a full-load power of unity over the period of 24 hrs. The maximum efficiency is 95% and it occurs at full-load. Calculate the all-day efficiency if loaded as follows:

6-hours at full-load

6 hours at quarter load

A. 91.53%

B. 92.45%

C. 90.37%

D. 93.86%

View Answer:

Answer: Option C

Solution:

19. EE Board Exam April 1995

Ideal transformer assumptions do not include

A. no leakage flux

B. no saturation of core

C. zero resistance of the winding

D. zero reactance of the winding

View Answer:

Answer: Option D

Solution:

20. EE Board Exam October 1993

A transformer is designed to carry 30 times its rated current for 1 second. The length of time that a current of 20 times the rated current can be allowed to flow is

A. 0.67 sec

B. 2 sec

C. 1.5 sec

D. 2.25 sec

View Answer:

Answer: Option D

Solution:

21. REE Board Exam October 1998

Which of the following given below is the eddy current loss not proportional to?

A. square of the thickness

B. square of the frequency

C. square of the load current of the laminated core

D. square of the flux density

View Answer:

Answer: Option C

Solution:

22. REE Board Exam October 1997

A small single transformer has 10.2 watts no load loss. The core has a volume of 750 cu. cm. The maximum flux density is 10,000 gauss and the hysteresis constant of core is 5 x 10-4. Using the Steinmetz law to find the hysteresis, determine the eddy current loss.

A. 4.55 watts

B. 5.55 watts

C. 3.55 watts

D. 2.55 watts

View Answer:

Answer: Option A

Solution:

23. EE Board Exam April 1992

When the emf in the two windings of a transformer are opposite in direction, the polarity is

A. positive

B. additive

C. negative

D. subtractive

View Answer:

Answer: Option D

Solution:

24. EE Board Exam October 1991

The copper loss of the transformer will

A. not be affected by a change in the power factor

B. decrease with a lowering of the power factor

C. increase with an increase of the power factor

D. increase with the lowering of the power factor

View Answer:

Answer: Option D

Solution:

25. EE Board Exam June 1990

Power lost due to alternating magnetization and demagnetization of the core material

A. copper loss

B. eddy current loss

C. hysteresis loss

D. rheostat loss

View Answer:

Answer: Option C

Solution:

26. EE Board Exam June 1990

In the open circuit test of the transformer the wattmeter reading is equal to

A. eddy current loss

B. current loss

C. hysteresis loss

D. core loss

View Answer:

Answer: Option D

Solution:

27. EE Board Exam October 1991

A 30-kVA; 2,400/240 volts, 60-Hz transformer has a full-load power of unity over the period of 24 hrs. The maximum efficiency is 95% and it occurs at full-load. Calculate the all-day efficiency if loaded 6-hours at full-load.

A. 78.90%

B. 88.38%

C. 89.67%

D. 92.45%

View Answer:

Answer: Option B

Solution:

28. EE Board Exam April 1991

A certain transformer has a ratio of 8:1. The primary winding resistance is 0.00283 Ω and has 1,165 more turns than the secondary winding. If the copper loss in the primary is 20% less than the secondary, calculate the resistance of the secondary winding.

A. 5.53 x 10-5 ohm

B. 2.56 x 10-4 ohm

C. 6.78 x 10-7 ohm

D. 4.18 x 10-5 ohm

View Answer:

Answer: Option A

Solution:

29. EE Board Exam October 1992

A 200-kVA transformer has an impedance of 15% and the power factor of the load is 85%. The primary voltage is 6,000 volts while the copper loss is 15 kW. Find the percentage voltage regulation.

A. 13.49%

B. 15.78%

C. 8.91%

D. 23.67%

View Answer:

Answer: Option A

Solution:

30. EE Board Exam June 1990

Transformer connection that can transform threephase system to two-phase system and vice versa

A. Scott or T-connection

B. open delta

C. autotransformer connection

D. wye-delta connection

View Answer:

Answer: Option A

Solution:

31. EE Board Exam June 1990

Which transformer has only one winding?

A. distribution transformer

B. power transformer

C. autotransformer

D. isolated winding transformer

View Answer:

Answer: Option C

Solution:

32. EE Board Exam April 1990

When the primary and secondary windings take the form of a common ring which is encircled by two or more rings of magnetic materials distributed around its periphery, the transformer is termed as

A. grounding transformer

B. regulating transformer

C. core type transformer

D. shell type transformer

View Answer:

Answer: Option D

Solution:

33. A transformer transforms

A. frequency

B. voltage

C. current

D. voltage and current

View Answer:

Answer: Option D

Solution:

34. Which of the following is not a basic element of a transformer?

A. Core

B. primary winding

C. secondary winding

D. mutual flux

View Answer:

Answer: Option D

Solution:

35. In an ideal transformer

A. windings have no resistance

B. core has no losses

C. core has infinite permeability

D. all of these

View Answer:

Answer: Option D

Solution:

36. The main purpose of using core in a transformer is to

A. decrease iron losses

B. prevent eddy current loss

C. eliminate magnetic hysteresis

D. decrease reluctance of the common magnetic circuit

View Answer:

Answer: Option D

Solution:

37. Transformer cores are laminated in order to

A. simplify its construction

B. minimize eddy current loss

C. reduce cost

D. reduce hysteresis

View Answer:

Answer: Option B

Solution:

38. A transformer having 1000 primary turns is connected to a 250-V a.c supply. For a secondary voltage of 400 V, the number of secondary turns should be

A. 1600

B. 250

C. 400

D. 1250

View Answer:

Answer: Option A

Solution:

39. The primary and secondary induce e.m.fs. E1 and E2 in a two-winding transformer are always

A. equal in magnitude

B. anti-phase with each other

C. in-phase with each other

D. determined by load on transformer secondary

View Answer:

Answer: Option  C

Solution:

40. A step-up transformer increases

A. voltage

B. current

C. power

D. frequency

View Answer:

Answer: Option A

Solution:

41. The primary and secondary windings of an ordinary 2-winding transformer always have

A. different number of turns

B. same size of copper wire

C. a common magnetic circuit

D. separate magnetic circuits

View Answer:

Answer: Option C

Solution:

42. In a transformer, the leakage flux of each winding is proportional to the current in that winding because

A. Ohm’s law applies to magnetic circuits

B. leakage paths do not saturate

C. the two windings are electrically isolated

D. mutual flux is confined to the core

View Answer:

Answer: Option B

Solution:

43. In a two-winding transformer, the e.m.f. per turn in secondary winding is always ____ the induced e.m.f. power turn in primary.

A. equal to K times

B. equal to 1/K times

C. equal to

D. greater than

View Answer:

Answer: Option C

Solution:

44. In relation to a transformer, the ratio 20:1 indicates that

A. there are 20 turns on primary one turn on secondary

B. secondary voltage is 1/20th of primary voltage

C. primary current is 20 times greater than the secondary current

D. for every 20 turns on primary, there is one turn on secondary

View Answer:

Answer: Option D

Solution:

45. In performing the short circuit test of a transformer

A. high voltage side is usually short circuited

B. low voltage side is usually short circuited

C. any side is short circuited with preference

D. none of these

View Answer:

Answer: Option B

Solution:

46. The equivalent resistance of the primary of a transformer having K = 5 and R1 = 0.1 ohm when referred to secondary becomes ____ ohm.

A. 0.5

B. 0.02

C. 0.004

D. 2.5

View Answer:

Answer: Option D

Solution:

47. A transformer has negative voltage regulation when its power factor is

A. zero

B. unity

C. leading

D. lagging

View Answer:

Answer: Option C

Solution:

48. The primary reason why open-circuit test is performed on the transformer is that it

A. draws sufficiently large no-load current for convenient reading

B. requires least voltage to perform the test

C. needs minimum power input

D. involves less core loss

View Answer:

Answer: Option A

Solution:

49. No-load test on a transformer is carried out to determine

A. copper loss

B. magnetizing current

C. magnetizing current and no-load loss

D. efficiency of the transformer

View Answer:

Answer: Option C

Solution:

50. The main purpose of performing open-circuit test on a transformer is to measure its

A. Cu loss

B. core loss

C. total loss

D. insulation resistance

View Answer:

Answer: Option B

Solution:

MCQ in Transformers Part 2 | REE Board Exam

DOWNLOAD PDF / PRINT
Print Friendly, PDF & Email
Please do Subscribe on YouTube!

P inoyBIX educates thousands of reviewers and students a day in preparation for their board examinations. Also provides professionals with materials for their lectures and practice exams. Help me go forward with the same spirit.

“Will you subscribe today via YOUTUBE?”

Subscribe

Add Comment

PinoyBIX Engineering. © 2014-2020 All Rights Reserved | How to Donate? | Follow me on Blogarama DMCA.com Protection Status

Math Solution

Advanced Math problem age work mixture digit motion Analytic Geometry 01 problem Analytic Geometry 02 problem clock variation progression misc Combination problem Differential Calculus 01 Problem Differential Calculus 02 Problem Differential Equations Problem Fundamentals in Algebra Fundamentals in Algebra Problem Integral Calculus problem Permutation problem Plane Geometry problem Plane Trigonometry problem Probability problem quadratic equation binomial theorem logarithms Solid Geometry problem Spherical Trigonometry problem System of Numbers Problem Venn Diagram Problem

Questions and Answers in Mathematics

Advanced Math Age Work Mixture Digit Motion Algebra and General Mathematics Analytic Geometry 01 Analytic Geometry 02 Calculus Clock Variation Progression Misc Differential Calculus 01 Differential Calculus 02 Differential Equations Engineering Mathematics Geometry Integral Calculus Plane Geometry Plane Trigonometry Probability and Statistics Quadratic Equation Binomial Theorem Logarithms Solid Geometry Spherical Trigonometry System of Numbers Trigonometry

video

Pre-board in Electronics Engineering

Answers Pre-board in Electronics Engineering - Answers

Questions and Answers

Basic Television - Grob TV Boylestad Questions and Answers Computer Principles Electrical Circuit Electricity and Magnetism Fundamentals Electronic Circuits Floyd Questions and Answers Floyd Self-test Gibilisco Questions and Answers Grob Questions and Answers Industrial Electronics Principles and Applications Malvino Questions and Answers Microelectronics Power Generators / Sources / Principles and Applications Solid State Devices Tests and Measurements Vacuum Tubes

Pre-board in Communications Engineering

Answers

Questions and Answers

Acoustics Antennas Blake Questions and Answers Broadcasting and Cable TV System Digital Communication Networks Forouzan Frenzel Self-test Kennedy Questions and Answers Microwave Communications Miscellaneous Questions in Communications Modulation Navigational Aids and Radar Systems Noise Optical Fiber Communications Radiation and Wave Propagation Satellite Communications Transmission Fundamentals Wire and Wireless Communications

GEAS Solution

Dynamics problem Economics problem Physics problem Statics problem Strength problem Thermodynamics problem

Pre-board in GEAS

Questions and Answers in GEAS

Engineering Economics Engineering Laws and Ethics Engineering Management Engineering Materials Engineering Mechanics General Chemistry Giancoli Physics Physics Strength of Materials Thermodynamics
Online Tool: Electrical Charge Conversions
Online Tool: Electrical Charge Conversions
Online Tool: Color Code Conversions
Online Tool: Color Code Conversions
Online Tool: Weight Measurement Conversions
Online Tool: Weight Measurement Conversions
Online Tool: Temperature Measurement Conversions
Online Tool: Temperature Measurement Conversions