BSNL TTA (JE) ELECTRICAL 200 EXPECTED QUESTIONS PART ONE

NOTE-NO OF QUESTIONS 116
ANSWER KEY-Correct answer is indicated by symbol (V) in options.
HINTS-In some questions options E-HINTS is indicating the hints of answer

SAMPLE QUESTIONS AND ANSWER
1) Eddy current loss will depends on
A [ ]) Frequency
B [ ]) Flux density
C [ ]) Thickness
D [v]) All of the above
E [ ]) HINTS-Eddy current loss=kf²Bm²
2) Hysteresis loss will depends on
A [v]) f
B [ ]) f²
C [ ]) f³
D [ ]) f½
3) Thin laminations are used in a machine in order to reduce
A [v]) Eddy current losses
B [ ]) Hysteresis losses
C [ ]) Both 1 and 2
D [ ]) Copper losses
E [ ]) HINTS-Thin laminations are used in order to reduce the eddy current losses only. Due to
laminations the area of the eddy currents loops are minimized and the losses due to eddy current
losses are minimized.
4) Hysteresis loop represents the area of
A [ ]) eddy current loss
B [ ]) copper loss
C [ ]) total iron losses
D [v]) hysteresis loss
E [ ]) HINTS-Hysteresis loop will represents only hysteresis losses. It is found out by area of B-H
loop curve of a magnetic material

5) Total core loss is also called as ————-?
A [ ]) Eddy current loss
B [ ]) Hysteresis loss
C [v]) Magnetic loss
D [ ]) Copper loss
E [ ]) HINTS-The total core loss or magnetic loss consists of eddy current loss and hysteresis
loss.
6) Which of the following are variable losses?
A [ ]) eddy current loss
B [ ]) hysteresis loss
C [ ]) shunt field copper loss
D [v]) armature copper loss
E [ ]) HINTS-Armature copper loss is directly proportional to square of armature current.
Therefore as the load varies these will also vary.
7) Maximum efficiency will occur, when copper loss is_______to iron loss?
A [ ]) greater than
B [ ]) less than
C [v]) equals to
D [ ]) any of the above
E [ ]) HINTS-Condition for maximum efficiency is, copper loss = iron loss or variable losses is
equals to fixed losses.
8) Autotransformer makes effective saving on copper and copper losses, when its
transformation ratio is equal to
A [ ]) very low
B [ ]) less than one.
C [ ]) greater than one.
D [v]) approx to one.
9) The basic function of a transformer is to change
A [ ]) the power level
B [ ]) the power factor

C [v]) the level of the voltage
D [ ]) the frequency
E [ ]) HINTS-A transformer can be used for either step up or step down the voltages. Its basic
application in power system is to transform the voltage from one level to another level without
changing its frequency and power.
10) Transformer action requires a
A [ ]) constant magnetic flux
B [ ]) increasing magnetic flux
C [v]) alternating magnetic lux
D [ ]) alternating electric flux
E [ ]) HINTS-The energy transfer from one winding to another is entirely through magnetic
medium it is known as transformer action based on the principle of electromagnetic induction
proposed by faraday. Therefore, transformer action requires an alternating or time varying
magnetic flux to transfer power from primary side to secondary side. Since induced emf in the
winding is due to flux linkage.

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