Single - Phase Transformer - Electrical Engineering (MCQ) questions and answers

1)   The steel used for laminations should have

a. High permeability and high hysteresis
b. High permeability and low hysteresis
c. Low permeability and hysteresis
d. Low permeability and high hysteresis
Answer  Explanation 

ANSWER: High permeability and low hysteresis

Explanation:
No explanation is available for this question!
2)   In core type transformer, the coils are wound in helical layers, each layers being insulated from each other by using

a. Paper
b. Cloth
c. Cooling ducts
d. All of these
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!
3)   Copper losses is proportional to

a. kVA
b. square of kVA
c. cube of kVA
d. none of these
Answer  Explanation 

ANSWER: square of kVA

Explanation:
No explanation is available for this question!
4)   The efficiency of the transformer will be maximum when

a. Iron losses is equal to the twice of the copper losses
b. Copper losses is equal to the twice of the iron losses
c. Iron losses is equal to the copper losses
d. All of these
Answer  Explanation 

ANSWER: Iron losses is equal to the copper losses

Explanation:
No explanation is available for this question!
5)   If R1 is the primary winding resistance and R2 is the secondary winding resistance then the equivalent resistance of the transformer as referred to the primary is

a. R1+ R2/K2
b. R2+ R1/K2
c. R1+ K2R2
d. R2+ K2R1
Answer  Explanation 

ANSWER: R1+ R2/K2

Explanation:
No explanation is available for this question!
6)   If ∅m is the maximum value of flux in the core then the average rate of change of flux is

a. f∅m
b. 2 f∅m
c. 4 f∅m
d. 4.44 f∅m
Answer  Explanation 

ANSWER: 4 f∅m

Explanation:
No explanation is available for this question!
7)   If the transformer is loaded then the secondary terminal voltage falls for and rises for

a. Lagging power factor, leading power factor
b. Lagging power factor, unity power factor
c. Unity power factor, lagging power factor
d. Leading power factor, lagging power factor
Answer  Explanation 

ANSWER: Lagging power factor, leading power factor

Explanation:
No explanation is available for this question!
8)   Efficiency of a transformer is maximum at

a. Leading power factor
b. Lagging power factor
c. Unity power factor
d. None of these
Answer  Explanation 

ANSWER: Unity power factor

Explanation:
No explanation is available for this question!
9)   Copper losses occurs due to ohmic resistance in

a. Primary winding
b. Secondary winding
c. Both primary and secondary winding
d. None of these
Answer  Explanation 

ANSWER: Both primary and secondary winding

Explanation:
No explanation is available for this question!
10)   In transformer if the secondary is open circuited then its terminal voltage is

a. Same as the induced emf
b. Greater than the induced emf
c. Lesser than the induced emf
d. None of these
Answer  Explanation 

ANSWER: Same as the induced emf

Explanation:
No explanation is available for this question!

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