Explore topic-wise MCQs in Transformers.

This section includes 293 Mcqs, each offering curated multiple-choice questions to sharpen your Transformers knowledge and support exam preparation. Choose a topic below to get started.

251.

In a 1-phase 250 / 3000 V, 50 Hz transformer, if the EMF per turn is 8 V and ILV = 400 A, determine the LV and HV side turns and power rating of the transformer.

A. NLV = 32, NHV = 375, Power rating: 100 kVA
B. NLV = 375, NHV = 32, Power rating: 100 kVA
C. NLV = 32, NHV = 375, Power rating: 10 kVA
D. NLV = 32, NHV = 375, Power rating: 1200 kVA
Answer» B. NLV = 375, NHV = 32, Power rating: 100 kVA
Discussion
252.

In the three phase delta transformer, one phase burns up. The transformer will supply

A. 57.7% of its rating
B. Zero output
C. 63% of its output rating
D. At full output rating
Answer» B. Zero output
Discussion
253.

If f is the opening current frequency of a magnetic circuit with a ferromagnetic core, then the hysteresis loss will be

A. \(\propto \ f\)
B. \(\propto \ f^2\)
C. \(\propto \ \frac{1}{f^2}\)
D. \(\propto \ \frac{1}{f}\)
Answer» B. \(\propto \ f^2\)
Discussion
254.

A transformer can have negative voltage regulation at:

A. Zero power factor
B. Leading power factor
C. Lagging power factor
D. Unity power factor
Answer» C. Lagging power factor
Discussion
255.

Eddy current losses in the transformer are

A. Directly proportional to the frequency squared
B. Inversely proportional to the thickness of the lamination
C. Inversely proportional to the field strength
D. Inversely proportional to the frequency
Answer» B. Inversely proportional to the thickness of the lamination
Discussion
256.

For matching a circuit of output impedance 200 ohms with a load of 8 ohms, the turns ratio of the two winding of transformer should be

A. 25
B. 1/25
C. 1/5
D. 5
Answer» E.
Discussion
257.

Auto transformer consists of _________ winding.

A. One
B. Two
C. Three
D. Four
Answer» B. Two
Discussion
258.

Buchholz relay is placed:

A. In between the conservator and the breather
B. In between the tank and the conservator
C. In between the h.v. winding and the bushing
D. In between the l.v. winging and the bushing
Answer» C. In between the h.v. winding and the bushing
Discussion
259.

In a transformer, an occurrence of dimensional changes, both perpendicular and parallel to the direction of magnetization, is referred to as:

A. Damping
B. Magnetostriction
C. Coupling
D. Oscillation
Answer» C. Coupling
Discussion
260.

Open Circuit Test on a transformer is used to find:

A. No-load currents
B. Full load copper loss
C. Equivalent resistance referred to metering side
D. Equivalent resistance referred to metering side and no-load current both
Answer» E.
Discussion
261.

Directions: It consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. You are to examine these two statements carefully and select the answer using the codes given below:Statement (I): Large power transformer testing under full load current is not possible.Statement (II): Short circuit test of transformer gives indication of copper loss.

A. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B. Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)
C. Statement (I) is true but Statement (II) is false
D. Statement (I) is false but Statement (II) is true
Answer» C. Statement (I) is true but Statement (II) is false
Discussion
262.

In a transformer, the resistive drop is 2% and reactive drop is 5%. What will be its regulation at full load unity power factor?

A. 1%
B. 5%
C. 2%
D. 7%
Answer» D. 7%
Discussion
263.

In a power transformer, the core loss is 50 W at 40 Hz and 100 W at 60 Hz, under the condition of same maximum flux density in both cases. The core loss at 50 Hz will be

A. 64 W
B. 73 W
C. 82 W
D. 91 W
Answer» C. 82 W
Discussion
264.

A 200/100 V, 50 Hz transformer is to be excited at 40 Hz from the 100 V side. For the exciting current to remain same, the applied voltage should be

A. 150 V
B. 125 V
C. 100 V
D. 80 V
Answer» E.
Discussion
265.

Input power supplied during a short-circuit test on a transformer equal:

A. Total losses
B. Iron loss
C. Copper loss
D. Output power
Answer» D. Output power
Discussion
266.

A single phase transformer has no load of 64 W, as obtained from an open circuit test. When a short circuit test is performed on it with 90% of the rated currents flowing in its both LV and HV winding. The measured loss is 81 W. The transformer has maximum efficiency when operated at:

A. 50.0% of the rated current
B. 64.0% of the rated current
C. 80.0% of the rated current
D. 88.8% of the rated current
Answer» D. 88.8% of the rated current
Discussion
267.

Average and rms values of induced emf per turn in a transformer are given as:

A. 4 f \(\phi_m \ V\) and 4.44 f \(\phi_m \ V\) respectively
B. 4 f \(\phi_m \ V\) and π f \(\phi_m\) V respectively
C. 4 f \(\phi_m \ V\) and 4 π f \(\phi_m\) respectively
D. \(4 \ f \ B_m \ V\)and 4.44 f \(B_m\) V respectively
Answer» B. 4 f \(\phi_m \ V\) and π f \(\phi_m\) V respectively
Discussion
268.

Consider the following statements regarding parallel operation of transformer’s1. Transformers must be operated at same frequency2. Transformers must have equal voltage ratingsWhich of the following statements is/are correct?

A. Only 1
B. Only 2
C. Both 1 and 2
D. Neither 1 nor 2
Answer» D. Neither 1 nor 2
Discussion
269.

In a single-phase transformer, the total iron loss is 2500 W at nominal voltage of 440 V and frequency 50 Hz. The total iron loss is 850 W at 220 V and 25 Hz. Then, at nominal voltage and frequency, the hysteresis loss and eddy current loss respectively are

A. 1600 W and 900 W
B. 900 W and 1600 W
C. 600 W and 250 W
D. 250 W and 600 W
Answer» C. 600 W and 250 W
Discussion
270.

A 400/200 volts transformer has pu impedance of 0.05. The HV side voltage required to circulate full load current during short circuit test is

A. 20 V
B. 40 V
C. 10 V
D. 5 V
Answer» B. 40 V
Discussion
271.

Magnetizing component of no load current _________.

A. lags behind the applied voltage by 65°
B. lags behind the applied voltage by 90°
C. leads the applied voltage by 150°
D. in line with applied voltage
Answer» C. leads the applied voltage by 150°
Discussion
272.

An ideal transformer is used to step down the voltage of a 230 V circuit to 23 V. It is fully loaded when it delivers 2.3 kVA. What is the rated current for low-voltage winding

A. 10 A
B. 1 A
C. 100 A
D. 0.1 A
Answer» D. 0.1 A
Discussion
273.

Directions: It consists of two statements one labeled as statement I and the other as statements II. Examine these two statements carefully and select the correct answer using the code given below.Statement I: The stator winding of a control transformer in a synchro pair has a high impedance per phase.Statement II: The rotor of the control transformer is cylindrical in shape.

A. Both statements I and statement II are individually true and statement II is the correct explanation of statement I
B. Both statement I and statement II are individually true but statement II is not the correct explanation of statement I
C. Statements I is true but statement II is false
D. Statement I is false but statement II is true
Answer» C. Statements I is true but statement II is false
Discussion
274.

A phase difference of 30 degree between input and output corresponding line voltages of three-phase transformer connection is to be obtained. The connection to be made is:

A. Delta-Zigzag
B. Delta-Delta
C. Star-Star
D. Star-Delta
Answer» E.
Discussion
275.

Directions: It consists of two statements, one labeled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answer using the codes given below:Statement (I): The core-loss in a transformer is independent of the load current.Statement (II): The core is made up of thin laminations interleaved at the joints to avoid air-gaps.

A. Statement (I) and Statement (II) are individually true and statement (II) is the correct explanation of statement (II)
B. Statement (I) and Statement (II) are individually true but statement (II) is not the correct explanation of statement (I)
C. Statement (I) is true but statement (II) is false
D. Statement (I) is false but statement (II) is true
Answer» C. Statement (I) is true but statement (II) is false
Discussion
276.

In the case of transformers, the increase in temperature is directly proportional to:

A. power factor
B. apparent power
C. leakage reactance
D. reactive power
Answer» C. leakage reactance
Discussion
277.

For a transformer, the load connected to the secondary has an impedance of 8 Ω. Its reflected impedance on primary is observed to be 648 Ω. The turns ratio of this transformer is

A. 6 : 1
B. 10 : 1
C. 9 : 1
D. 8 : 1
Answer» D. 8 : 1
Discussion
278.

Directions: It consists of two statements, one labeled as ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answer using the code given below:Statement (I): An autotransformer is economical in using copper in its manufacture.Statement (II): The sector of the winding common to both primary and secondary circuits carries only the difference of primary and secondary currents.

A. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement(I)
C. Statement (I) is true but Statement (II) us false
D. Statement (I) is false but Statement (II) is true
Answer» C. Statement (I) is true but Statement (II) us false
Discussion
279.

WHICH_OF_THE_FOLLOWING_IS_THE_EXPRESSION_FOR_EMF_INDUCED_IN_PRIMARY_WITH_VOLTAGE_APPLIED_TO_PRIMARY_OF_AN_IDEAL_TRANSFORMER??$

A. e=V
B. V= √2*e*cos ωt
C. e= √2*V*cos ωt
D. Cannot say
Answer» D. Cannot say
Discussion
280.

For transformer given, turns ratio is equal to a, what will be the impedance of primary with respect to secondary?$

A. a<sup>2</sup> times the secondary impedance
B. a times secondary impedance
C. secondary impedance/a
D. secondary impedance/a<sup>2</sup>
Answer» E.
Discussion
281.

Which of the following is the wrong expression?$

A. i<sub>1</sub>N<sub>1</sub>=i<sub>2</sub>N<sub>2</sub>
B. i<sub>1</sub>v<sub>1</sub>=i<sub>2</sub>v<sub>2</sub>
C. i<sub>1</sub>N2=i<sub>2</sub>N<sub>1</sub>
D. v<sub>2</sub>N<sub>1</sub>=v<sub>1</sub>N<sub>2</sub>
Answer» D. v<sub>2</sub>N<sub>1</sub>=v<sub>1</sub>N<sub>2</sub>
Discussion
282.

For a transformer with primary turns 400, secondary turns 100, if 20A current is flowing through primary, we will get ___________

A. 80A at secondary
B. 5A at secondary
C. 800A at secondary
D. 40A at secondary
Answer» B. 5A at secondary
Discussion
283.

For a transformer with primary turns 100, secondary turns 400, if 200 V is applied at primary we will get ___________

A. 80 V at secondary
B. 800 V at secondary
C. 1600 V at secondary
D. 3200 V at secondary
Answer» C. 1600 V at secondary
Discussion
284.

Power transformed in the ideal transformer with turns ratio a is _______

A. a<sup>2</sup> times primary
B. a times primary
C. primary power/ a<sup>2</sup>
D. primary power
Answer» E.
Discussion
285.

Which of the following statement is correct regarding turns ratio?

A. Current ratio and turns ratio are inverse of each other
B. Current ratio is exactly same to the voltage ratio
C. Currents ratio is exactly same to the turns ratio
D. Voltage ratio and turns ratio are inverse of each other
Answer» B. Current ratio is exactly same to the voltage ratio
Discussion
286.

Turns ratio of the transformer is directly proportional to ____________

A. Resistance ratio
B. Currents ratio
C. Voltage ratio
D. Not proportional to any terms
Answer» D. Not proportional to any terms
Discussion
287.

Ideal transformer core has permeability equal to _____

A. Zero
B. Non-zero finite
C. Negative
D. Infinite
Answer» E.
Discussion
288.

Which of the following statement regarding an ideal single-phase transformer is incorrect? Transformer is having a turn ratio of 1: 2 and drawing a current of 10 A from 200 V AC supply is incorrect?

A. It’s a step-up transformer
B. Its secondary voltage is 400 V
C. Its rating is 2 kVA
D. Its secondary current is 20 A
Answer» E.
Discussion
289.

An ideal transformer will have maximum efficiency at a load such that _____________

A. copper loss = iron loss
B. copper loss < iron loss
C. copper loss > iron loss
D. cannot be determined
Answer» B. copper loss < iron loss
Discussion
290.

Identify the correct statement relating to the ideal transformer.

A. no losses and magnetic leakage
B. interleaved primary and secondary windings
C. a common core for its primary and secondary windings
D. core of stainless steel and winding of pure copper metal
Answer» B. interleaved primary and secondary windings
Discussion
291.

In a transformer the resistance between its primary and secondary is ______________

A. Zero
B. Very small
C. Cannot be predicted
D. Infinite
Answer» E.
Discussion
292.

An ideal transformer has infinite primary and secondary inductances.

A. True
B. False
Answer» C.
Discussion
293.

A transformer cannot work on the DC supply because __________________

A. There is no need to change the DC voltage
B. A DC circuit has more losses
C. Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero
D. Cannot be determined
Answer» D. Cannot be determined
Discussion