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Transformers

Study 132 Electrical Engineering MCQs with correct answers and explanations.

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101Electrical EngineeringMedium

The magnetising current of a transformer is usually small because it has________?

Afewer rotating parts

Blaminated silicon steel core

Clarge leakage flux

Dsmall air gap

Correct answer

D. small air gap

Explanation

The correct answer is small air gap.

102Electrical EngineeringMedium

Which of the following property is not necessarily desirable in the material for transformer core?

ALow hysteresis loss

BHigh thermal conductivity

CHigh permeability

DMechanical strength

Correct answer

B. High thermal conductivity

Explanation

The correct answer is High thermal conductivity.

103Electrical EngineeringMedium

The efficiencies of transformers compared with that of electric motors of the same power are________?

Amuch smaller

Bmuch higher

Cabout the same

Dnone of the above

Esomewhat smaller

Correct answer

B. much higher

Explanation

The correct answer is much higher.

104Electrical EngineeringMedium

An ideal transformer changes which electrical quantities while transferring power between circuits?

ACurrent only

BVoltage only

CVoltage and current

DFrequency

Correct answer

C. Voltage and current

Explanation

The correct answer is Voltage and current.

105Electrical EngineeringMedium

The maximum load that a power transformer can carry is limited by its________?

Atemperature rise

Bcopper loss

Cdielectric strength of oil

Dvoltage ratio

Correct answer

D. voltage ratio

Explanation

The correct answer is voltage ratio.

106Electrical EngineeringMedium

Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is________?

Aapproximately equal to one

Bless than one

Cnone of the above

Dgreat than one

Correct answer

A. approximately equal to one

Explanation

The correct answer is approximately equal to one.

107Electrical EngineeringMedium

The chemical used in breather for transformer should have the quality of________?

Acooling the transformer oil

Bcleansing the transformer oil

Cionizing air

Dabsorbing moisture

Correct answer

D. absorbing moisture

Explanation

The correct answer is absorbing moisture.

108Electrical EngineeringMedium

The size of a transformer core will depend on________?

Afrequency

Barea of the core

CA. and B. both

Dflux density of the core material

Correct answer

C. A. and B. both

Explanation

The correct answer is A. and B. both.

109Electrical EngineeringMedium

Losses which occur in rotating electric machines and do not occur in transformers are________?

Acopper losses

Bhysteresis and eddy current losses

Cmagnetic losses

Dfriction and windage losses

Correct answer

D. friction and windage losses

Explanation

The correct answer is friction and windage losses.

110Electrical EngineeringMedium

For the parallel operation of single phase transformers it is necessary that they should have________?

Asame number of turns on the secondary side.

Bsame polarity

Csame efficiency

Dsame kVA rating

Correct answer

B. same polarity

Explanation

The correct answer is same polarity.

101Electrical EngineeringMedium

The magnetising current of a transformer is usually small because it has________?

Afewer rotating parts

Blaminated silicon steel core

Clarge leakage flux

Dsmall air gap

Correct answer

D. small air gap

Explanation

The correct answer is small air gap.

102Electrical EngineeringMedium

Which of the following property is not necessarily desirable in the material for transformer core?

ALow hysteresis loss

BHigh thermal conductivity

CHigh permeability

DMechanical strength

Correct answer

B. High thermal conductivity

Explanation

The correct answer is High thermal conductivity.

103Electrical EngineeringMedium

The efficiencies of transformers compared with that of electric motors of the same power are________?

Amuch smaller

Bmuch higher

Cabout the same

Dnone of the above

Esomewhat smaller

Correct answer

B. much higher

Explanation

The correct answer is much higher.

104Electrical EngineeringMedium

An ideal transformer changes which electrical quantities while transferring power between circuits?

ACurrent only

BVoltage only

CVoltage and current

DFrequency

Correct answer

C. Voltage and current

Explanation

The correct answer is Voltage and current.

105Electrical EngineeringMedium

The maximum load that a power transformer can carry is limited by its________?

Atemperature rise

Bcopper loss

Cdielectric strength of oil

Dvoltage ratio

Correct answer

D. voltage ratio

Explanation

The correct answer is voltage ratio.

106Electrical EngineeringMedium

Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is________?

Aapproximately equal to one

Bless than one

Cnone of the above

Dgreat than one

Correct answer

A. approximately equal to one

Explanation

The correct answer is approximately equal to one.

107Electrical EngineeringMedium

The chemical used in breather for transformer should have the quality of________?

Acooling the transformer oil

Bcleansing the transformer oil

Cionizing air

Dabsorbing moisture

Correct answer

D. absorbing moisture

Explanation

The correct answer is absorbing moisture.

108Electrical EngineeringMedium

The size of a transformer core will depend on________?

Afrequency

Barea of the core

CA. and B. both

Dflux density of the core material

Correct answer

C. A. and B. both

Explanation

The correct answer is A. and B. both.

109Electrical EngineeringMedium

Losses which occur in rotating electric machines and do not occur in transformers are________?

Acopper losses

Bhysteresis and eddy current losses

Cmagnetic losses

Dfriction and windage losses

Correct answer

D. friction and windage losses

Explanation

The correct answer is friction and windage losses.

110Electrical EngineeringMedium

For the parallel operation of single phase transformers it is necessary that they should have________?

Asame number of turns on the secondary side.

Bsame polarity

Csame efficiency

Dsame kVA rating

Correct answer

B. same polarity

Explanation

The correct answer is same polarity.