Transformers Multiple Choice Questions and Answers Preparation for Competition exams pdf

1.  Which of the following does not change in a transformer ?
(a)  Current   
(b) Voltage
(c) Frequency   
(d) All of the above
Ans: c

2.  In a transformer the energy is conveyed from primary to secondary
(a)    through cooling coil
(b)    through air
(c)    by the flux
(d)    none of the above
Ans: c

3.    A transformer core is laminated to
(a)    reduce hysteresis loss
(b)    reduce eddy current losses
(c)    reduce copper losses
(d)    reduce all above losses
Ans: b

4.    The degree of mechanical vibrations produced by the laminations of a transformer depends on
(a)    tightness of clamping
(b)    gauge of laminations
(c)    size of laminations
(d)     all of the above
Ans: d

5.    The no-load current drawn by transformer is usually what per cent of the full-load current ?
(a)    0.2 to 0.5 per cent
(b)    2 to 5 per cent
(c)    12 to 15 per cent
(d)    20 to 30 per cent
Ans: b

6.    The path of a magnetic flux in a transformer should have
(a) high resistance
(b) high reluctance
(c) low resistance 
(d) low reluctance
Ans: d

7.    No-load on a transformer is carried out to determine
(a)    copper loss
(b)    magnetising current
(c)    magnetising current and loss
(d)    efficiency of the transformer
Ans: c

8.    The dielectric strength of transformer oil is expected to be
(a)  lkV   
(b)  33 kV
(c)  100 kV   
(d) 330 kV
Ans: b

9.   Sumpner's test is conducted on trans-formers to determine
(a)     temperature     
(b)     stray losses
(c)    all-day efficiency
(d)    none of the above
Ans: a

10.    The permissible flux density in case of cold rolled grain oriented steel is around
(a) 1.7 Wb/m2   
(b) 2.7 Wb/m2
(c) 3.7 Wb/m2   
(d) 4.7 Wb/m2
Ans: a

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