When secondary of a current transformer is open-circuited its iron core will be__________?

hot because primary will carry heavy current

hot because of heavy iron losses taking place in it due to high flux density

hot because primary will carry heavy current

cool as there is no secondary current

When a given transformer is run at its rated voltage but reduced frequency, its____________?

flux density remains unaffected

Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?

short-circuiting of the secondaries

power factor of one of the transformers is leading while that of the other lagging

transformers having higher copper losses will have negligible core losses

loading of the transformers not in proportion to their kVA ratings

The voltage transformation ratio of a transformer is equal to the ratio of_______________?

secondary terminal voltage to primary applied voltage

primary turns to secondary turns

secondary current to primary current

secondary induced e.m.f. to primary induced e.m.f

secondary terminal voltage to primary applied voltage

The size of a transformer core will depend on__________?

flux density of the core material

The secondary of a current transformer is always short-circuited under operating conditions because it____________________?

avoids core saturation and high voltage induction

The purpose of providing iron core in a step-up transformer is?

to provide coupling between primary and secondary

to increase the magnitude of mutual flux

to decrease the magnitude of mag-netizing current

The purpose of providing an iron core in a transformer is to_____________?

decrease the reluctance of the magnetic path

The leakage flux in a transformer depends upon______________?

load current, voltage and frequency

load current, voltage, frequency and power factor

The function of conservator in a transformer is___________________?

to project against’internal fault

to reduce copper as well as core losses

to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings

The function of breather in a transformer is___________?

to provide oxygen inside the tank

to cool the coils during reduced load

to arrest flow of moisture when outside air enters the transformer

The efficiency of a transformer will be maximum when_____________?

copper losses = hysteresis losses

hysteresis losses = eddy current losses

eddy current losses = copper losses

The efficiency of a transformer, under heavy loads, is comparatively low because_______________?

iron loss is increased considerably

copper loss becomes high in proportion to the output

iron loss is increased considerably

voltage drop both in primary and secondary becomes large

secondary output is much less as compared to primary input

113 + Mcqs in Transformers in Electrical Engineering Questions Page 1 McqOptions

1.	Which type of winding is used in 3 phase shell-type transformer?
A.	Circular type
B.	Sandwich type
C.	Cylindrical type
D.	Rectangular type
Answer» C. Cylindrical type

Discussion

2.	Which of the following protection is normally not provided on small distribution transformers ?
A.	Overfluxing protection
B.	Buchholz relay
C.	Overcurrent protection
D.	All of the above
Answer» C. Overcurrent protection

Discussion

3.	Which of the following property is not necessarily desirable in the material for transformer core ?
A.	Mechanical strength
B.	Low hysteresis loss
C.	High thermal conductivity
D.	High permeability
Answer» D. High permeability

Discussion

4.	Which of the following properties is not necessarily desirable for the material for transformer core ?
A.	Low hysteresis loss
B.	High permeability
C.	High thermal conductivity
D.	Adequate mechanical strength
Answer» D. Adequate mechanical strength

Discussion

5.	Which of the following loss in a transformer is zero even at full load ____________?
A.	Core loss
B.	Friction loss
C.	Eddy current loss
D.	Hysteresis loss
Answer» C. Eddy current loss

Discussion

6.	Which of the following is not a routine test on transformers ?
A.	Core insulation voltage test
B.	Impedance test
C.	Radio interference test
D.	Polarity test
Answer» D. Polarity test

Discussion

7.	Which of the following insulating materials can withstand the highest temperature safely ?
A.	Cellulose
B.	Asbestos
C.	Mica
D.	Glass fibre
Answer» D. Glass fibre

Discussion

8.	When secondary of a current transformer is open-circuited its iron core will be__________?
A.	hot because of heavy iron losses taking place in it due to high flux density
B.	hot because primary will carry heavy current
C.	cool as there is no secondary current
D.	none of above will happen
Answer» B. hot because primary will carry heavy current

Discussion

9.	When a given transformer is run at its rated voltage but reduced frequency, its____________?
A.	flux density remains unaffected
B.	iron losses are reduced
C.	core flux density is reduced
D.	core flux density is increased
Answer» E.

Discussion

10.	Two transformers operating in parallel will share the load depending upon their____________?
A.	leakage reactance
B.	per unit impedance
C.	efficiencies
D.	ratings
Answer» C. efficiencies

Discussion

11.	Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?
A.	short-circuiting of the secondaries
B.	power factor of one of the transformers is leading while that of the other lagging
C.	transformers having higher copper losses will have negligible core losses
D.	loading of the transformers not in proportion to their kVA ratings
Answer» E.

Discussion

12.	Transformer breaths in when_______________?
A.	load on it increases
B.	load on it decreases
C.	load remains constant
D.	none of the above
Answer» C. load remains constant

Discussion

13.	The voltage transformation ratio of a transformer is equal to the ratio of_______________?
A.	primary turns to secondary turns
B.	secondary current to primary current
C.	secondary induced e.m.f. to primary induced e.m.f
D.	secondary terminal voltage to primary applied voltage
Answer» D. secondary terminal voltage to primary applied voltage

Discussion

14.	The value of flux involved m the e.m.f. equation of a transformer is____________?
A.	average value
B.	r.m.s. value
C.	maximum value
D.	instantaneous value
Answer» D. instantaneous value

Discussion

15.	The use of higher flux density in the transformer design____________?
A.	reduces weight per kVA
B.	reduces iron losses
C.	reduces copper losses
D.	increases part load efficiency
Answer» B. reduces iron losses

Discussion

16.	The transformer ratings are usually expressed in terms of______________?
A.	volts
B.	amperes
C.	kW
D.	kVA
Answer» E.

Discussion

17.	The transformer oil should have _______ volatility and _______ viscosity?
A.	low,low
B.	high,high
C.	low,high
D.	high,low
Answer» B. high,high

Discussion

18.	The transformer lamination’s are insulated from each other by____________?
A.	mica strip
B.	thin coat of varnish
C.	paper
D.	any of the above
Answer» C. paper

Discussion

19.	The thickness of laminations used in a transformer is usually____________?
A.	0.4 mm to 0.5 mm
B.	4 mm to 5 mm
C.	14 mm to 15 mm
D.	25 mm to 40 mm
Answer» B. 4 mm to 5 mm

Discussion

20.	The size of a transformer core will depend on__________?
A.	frequency
B.	area of the core
C.	flux density of the core material
D.	A. and B. both
Answer» E.

Discussion

21.	The secondary of a current transformer is always short-circuited under operating conditions because it____________________?
A.	avoids core saturation and high voltage induction
B.	is safe to human beings
C.	protects the primary circuit
D.	none of the above
Answer» B. is safe to human beings

Discussion

22.	The purpose of providing iron core in a step-up transformer is?
A.	to provide coupling between primary and secondary
B.	to increase the magnitude of mutual flux
C.	to decrease the magnitude of mag-netizing current
D.	to provide all above features
Answer» E.

Discussion

23.	The purpose of providing an iron core in a transformer is to_____________?
A.	provide support to windings
B.	reduce hysteresis loss
C.	decrease the reluctance of the magnetic path
D.	reduce eddy current losses
Answer» D. reduce eddy current losses

Discussion

24.	The power transformer is a constant______________?
A.	voltage device
B.	current device
C.	power device
D.	main flux device
Answer» E.

Discussion

25.	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
Answer» B. 2.7 Wb/m2

Discussion

26.	The path of a magnetic flux in a transformer should have______________?
A.	high resistance
B.	high reluctance
C.	low resistance
D.	low reluctance
Answer» E.

Discussion

27.	The path of the magnetic flux in transformer should have____________?
A.	high reluctance
B.	low reactance
C.	high resistance
D.	low resistance
Answer» C. high resistance

Discussion

28.	The noise produced by a transformer is termed as_______________________?
A.	zoom
B.	hum
C.	ringing
D.	buzz
Answer» C. ringing

Discussion

29.	The noise resulting from vibrations of laminations set by magnetic forces, is termed as_________________?
A.	magnetostrication
B.	boo
C.	hum
D.	zoom
Answer» D. zoom

Discussion

30.	The no load current in a transformer lags behind the applied voltage by an angle of about_____________?
A.	180°
B.	120″
C.	90°
D.	75°
Answer» D. 75°

Discussion

31.	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
Answer» C. 12 to 15 per cent

Discussion

32.	The maximum load that a power transformer can carry is limited by its________________?
A.	temperature rise
B.	dielectric strength of oil
C.	voltage ratio
D.	copper loss
Answer» D. copper loss

Discussion

33.	The maximum efficiency of a distribution transformer is____________?
A.	at no load
B.	at 50% full load
C.	at 80% full load
D.	at full load
Answer» C. at 80% full load

Discussion

34.	The main reason for generation of harmonics in a transformer could be_______________?
A.	fluctuating load
B.	poor insulation
C.	mechanical vibrations
D.	saturation of core
Answer» E.

Discussion

35.	The magnetising current of a transformer is usually small because it has___________?
A.	small air gap
B.	large leakage flux
C.	laminated silicon steel core
D.	fewer rotating parts
Answer» B. large leakage flux

Discussion

36.	The leakage flux in a transformer depends upon______________?
A.	load current
B.	load current and voltage
C.	load current, voltage and frequency
D.	load current, voltage, frequency and power factor
Answer» B. load current and voltage

Discussion

37.	The hum in a transformer is mainly attributed to______________?
A.	load changes
B.	oil in the transformer
C.	magnetostriction
D.	mechanical vibrations
Answer» D. mechanical vibrations

Discussion

38.	The function of conservator in a transformer is___________________?
A.	to project against’internal fault
B.	to reduce copper as well as core losses
C.	to cool the transformer oil
D.	to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings
Answer» E.

Discussion

39.	The function of breather in a transformer is___________?
A.	to provide oxygen inside the tank
B.	to cool the coils during reduced load
C.	to cool the transformer oil
D.	to arrest flow of moisture when outside air enters the transformer
Answer» E.

Discussion

40.	The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be___________?
A.	6400 W
B.	1600 W
C.	800 W
D.	400 W
Answer» E.

Discussion

41.	The efficiency of two identical transformers under load conditions can be determined by_______________?
A.	short-circuit test
B.	back-to-back test
C.	open circuit test
D.	any of the above
Answer» C. open circuit test

Discussion

42.	The efficiency of a transformer will be maximum when_____________?
A.	copper losses = hysteresis losses
B.	hysteresis losses = eddy current losses
C.	eddy current losses = copper losses
D.	copper losses = iron losses
Answer» E.

Discussion

43.	The efficiency of a transformer, under heavy loads, is comparatively low because_______________?
A.	copper loss becomes high in proportion to the output
B.	iron loss is increased considerably
C.	voltage drop both in primary and secondary becomes large
D.	secondary output is much less as compared to primary input
Answer» B. iron loss is increased considerably

Discussion

44.	The efficiencies of transformers compared with that of electric motors of the same power are____________?
A.	about the same
B.	much smaller
C.	much higher
D.	somewhat smaller
E.	none of the above
Answer» D. somewhat smaller

Discussion

45.	The dielectric strength of transformer oil is expected to be______________?
A.	lkV
B.	33 kV
C.	100 kV
D.	330 kV
Answer» C. 100 kV

Discussion

46.	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
Answer» E.

Discussion

47.	The core used in high frequency transformer is usually___________?
A.	copper core
B.	cost iron core
C.	air core
D.	mild steel core
Answer» D. mild steel core

Discussion

48.	The chemical used in breather for transformer should have the quality of____________?
A.	ionizing air
B.	absorbing moisture
C.	cleansing the transformer oil
D.	cooling the transformer oil
Answer» C. cleansing the transformer oil

Discussion

49.	The chemical used in breather is_______________?
A.	asbestos fiber
B.	silica sand
C.	sodium chloride
D.	silica gel
Answer» E.

Discussion

50.	The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?
A.	Conservator
B.	Breather
C.	Bushings
D.	Buchholz relay
Answer» B. Breather

Discussion

Explore topic-wise MCQs in Electrical Engineering Questions.

Which type of winding is used in 3 phase shell-type transformer?

Which of the following protection is normally not provided on small distribution transformers ?

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

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

Which of the following loss in a transformer is zero even at full load ____________?

Which of the following is not a routine test on transformers ?

Which of the following insulating materials can withstand the highest temperature safely ?

When secondary of a current transformer is open-circuited its iron core will be__________?

When a given transformer is run at its rated voltage but reduced frequency, its____________?

Two transformers operating in parallel will share the load depending upon their____________?

Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?

Transformer breaths in when_______________?

The voltage transformation ratio of a transformer is equal to the ratio of_______________?

The value of flux involved m the e.m.f. equation of a transformer is____________?

The use of higher flux density in the transformer design____________?

The transformer ratings are usually expressed in terms of______________?

The transformer oil should have _______ volatility and _______ viscosity?

The transformer lamination’s are insulated from each other by____________?

The thickness of laminations used in a transformer is usually____________?

The size of a transformer core will depend on__________?

The secondary of a current transformer is always short-circuited under operating conditions because it____________________?

The purpose of providing iron core in a step-up transformer is?

The purpose of providing an iron core in a transformer is to_____________?

The power transformer is a constant______________?

The permissible flux density in case of cold rolled grain oriented steel is around__________?

The path of a magnetic flux in a transformer should have______________?

The path of the magnetic flux in transformer should have____________?

The noise produced by a transformer is termed as_______________________?

The noise resulting from vibrations of laminations set by magnetic forces, is termed as_________________?

The no load current in a transformer lags behind the applied voltage by an angle of about_____________?

The no-load current drawn by transformer is usually what per cent of the full-load current ?

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

The maximum efficiency of a distribution transformer is____________?

The main reason for generation of harmonics in a transformer could be_______________?

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

The leakage flux in a transformer depends upon______________?

The hum in a transformer is mainly attributed to______________?

The function of conservator in a transformer is___________________?

The function of breather in a transformer is___________?

The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be___________?

The efficiency of two identical transformers under load conditions can be determined by_______________?

The efficiency of a transformer will be maximum when_____________?

The efficiency of a transformer, under heavy loads, is comparatively low because_______________?

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

The dielectric strength of transformer oil is expected to be______________?

The degree of mechanical vibrations produced by the laminations of a transformer depends on____________?

The core used in high frequency transformer is usually___________?

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

The chemical used in breather is_______________?

The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?

The transformer oil should have _ volatility and _ viscosity?