IES Electrical Engineering Topic Wise Questions - UPSC PDF Download

 Page 1


IES Electrical Engineering Topic wise Questions
Electrical Machines
www.gatehelp.com
YEAR 2008
MCQ 1
Consider the following statements:
Skewing of rotors slots in a 3-phase induction motor (cage rotor) may
1. introduce additional leakage reactance
2. eliminate slot harmonics
Which of the statements given above is/are correct ?
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
MCQ 2
In the equivalent circuit of a double-cage induction motor, the two 
rotor cages can be considered
(A) to be in parallel
(B) to be in series-parallel
(C) to be in series
(D) to be in parallel with stator
MCQ 3
A 3-phase squirrel-cage induction motor is started by means of a 
Page 2


IES Electrical Engineering Topic wise Questions
Electrical Machines
www.gatehelp.com
YEAR 2008
MCQ 1
Consider the following statements:
Skewing of rotors slots in a 3-phase induction motor (cage rotor) may
1. introduce additional leakage reactance
2. eliminate slot harmonics
Which of the statements given above is/are correct ?
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
MCQ 2
In the equivalent circuit of a double-cage induction motor, the two 
rotor cages can be considered
(A) to be in parallel
(B) to be in series-parallel
(C) to be in series
(D) to be in parallel with stator
MCQ 3
A 3-phase squirrel-cage induction motor is started by means of a 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 2
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star/delta switch. What is the starting current of the motor ?
(A) 3 times the current with direct on line starting
(B) 1/3 times the current with direct on line starting
(C) / 13 times the current with direct on line starting
(D) 3 times the current with direct on line starting
MCQ 4
Sludge formation in transformer oil is due to which one of the following 
?
(A) Ingress of duct particles and moisture in the oil
(B) Appearance of small fragments of paper, varnish, cotton and 
other organic materials in the oil
(C) Chemical reaction of transformer oil with the insulating materials
(D) Oxidation of transformer oil
MCQ 5
A single-phase transformer rated for 220/440 V, 50 Hz operates at 
no load at 220 V, 40 Hz. This frequency operation at rated voltage 
results in which one of the following ?
(A) Increase of both eddy-current and hysteresis losses
(B) Reduction of both eddy-current and hysteresis losses
(C) Reduction of hysteresis loss and increase in eddy-current loss
(D) Increase of hysteresis loss and no change in the eddy-current loss
MCQ 6
What is the load at which maximum efficiency occurs in case of a 100 
kVA transformer with iron loss of 1 kW and full-load copper loss of 
2 kW ?
(A) 100 kVA
(B) 70.7 kVA
(C) 50.5 kVA
(D) 25.2 kVA
MCQ 7
Cores of large power transformers are made from which one of the 
Page 3


IES Electrical Engineering Topic wise Questions
Electrical Machines
www.gatehelp.com
YEAR 2008
MCQ 1
Consider the following statements:
Skewing of rotors slots in a 3-phase induction motor (cage rotor) may
1. introduce additional leakage reactance
2. eliminate slot harmonics
Which of the statements given above is/are correct ?
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
MCQ 2
In the equivalent circuit of a double-cage induction motor, the two 
rotor cages can be considered
(A) to be in parallel
(B) to be in series-parallel
(C) to be in series
(D) to be in parallel with stator
MCQ 3
A 3-phase squirrel-cage induction motor is started by means of a 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 2
www.gatehelp.com
star/delta switch. What is the starting current of the motor ?
(A) 3 times the current with direct on line starting
(B) 1/3 times the current with direct on line starting
(C) / 13 times the current with direct on line starting
(D) 3 times the current with direct on line starting
MCQ 4
Sludge formation in transformer oil is due to which one of the following 
?
(A) Ingress of duct particles and moisture in the oil
(B) Appearance of small fragments of paper, varnish, cotton and 
other organic materials in the oil
(C) Chemical reaction of transformer oil with the insulating materials
(D) Oxidation of transformer oil
MCQ 5
A single-phase transformer rated for 220/440 V, 50 Hz operates at 
no load at 220 V, 40 Hz. This frequency operation at rated voltage 
results in which one of the following ?
(A) Increase of both eddy-current and hysteresis losses
(B) Reduction of both eddy-current and hysteresis losses
(C) Reduction of hysteresis loss and increase in eddy-current loss
(D) Increase of hysteresis loss and no change in the eddy-current loss
MCQ 6
What is the load at which maximum efficiency occurs in case of a 100 
kVA transformer with iron loss of 1 kW and full-load copper loss of 
2 kW ?
(A) 100 kVA
(B) 70.7 kVA
(C) 50.5 kVA
(D) 25.2 kVA
MCQ 7
Cores of large power transformers are made from which one of the 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 3
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following ?
(A) Hot-rolled steel
(B) Cold-rolled non-grain oriented steel
(C) Cold-rolled grain oriented steel
(D) Ferrite
MCQ 8
A transformer has a percentage resistance of 2% and percentage 
reactance of 4%. What are its regulations at power factor 0.8 lagging 
and 0.8 leading, respectively ?
(A) 4% and 0.8% -
(B) 3.2% and 1.6% -
(C) 1.6% and 3.2% -
(D) 4.8% and 0.6% -
MCQ 9
The full-load copper loss and iron loss of a transformer are 6400 W 
and 5000 W, respectively. What are the above copper loss and iron 
loss, respectively at half-load ?
(A) 3200 W, 2500 W
(B) 3200 W, 5000 W
(C) 1600 W, 1250 W
(D) 1600 W, 5000 W
MCQ 10
Assertion (A) : A d.c motor draws high current at the time of starting.
Reason (R) : While starting a d.c. motor, it takes some time to 
develop a non-zero value of back e.m.f.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 11
Assertion (A) : For a 3-phase alternator operating on leading p.f. at 
Page 4


IES Electrical Engineering Topic wise Questions
Electrical Machines
www.gatehelp.com
YEAR 2008
MCQ 1
Consider the following statements:
Skewing of rotors slots in a 3-phase induction motor (cage rotor) may
1. introduce additional leakage reactance
2. eliminate slot harmonics
Which of the statements given above is/are correct ?
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
MCQ 2
In the equivalent circuit of a double-cage induction motor, the two 
rotor cages can be considered
(A) to be in parallel
(B) to be in series-parallel
(C) to be in series
(D) to be in parallel with stator
MCQ 3
A 3-phase squirrel-cage induction motor is started by means of a 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 2
www.gatehelp.com
star/delta switch. What is the starting current of the motor ?
(A) 3 times the current with direct on line starting
(B) 1/3 times the current with direct on line starting
(C) / 13 times the current with direct on line starting
(D) 3 times the current with direct on line starting
MCQ 4
Sludge formation in transformer oil is due to which one of the following 
?
(A) Ingress of duct particles and moisture in the oil
(B) Appearance of small fragments of paper, varnish, cotton and 
other organic materials in the oil
(C) Chemical reaction of transformer oil with the insulating materials
(D) Oxidation of transformer oil
MCQ 5
A single-phase transformer rated for 220/440 V, 50 Hz operates at 
no load at 220 V, 40 Hz. This frequency operation at rated voltage 
results in which one of the following ?
(A) Increase of both eddy-current and hysteresis losses
(B) Reduction of both eddy-current and hysteresis losses
(C) Reduction of hysteresis loss and increase in eddy-current loss
(D) Increase of hysteresis loss and no change in the eddy-current loss
MCQ 6
What is the load at which maximum efficiency occurs in case of a 100 
kVA transformer with iron loss of 1 kW and full-load copper loss of 
2 kW ?
(A) 100 kVA
(B) 70.7 kVA
(C) 50.5 kVA
(D) 25.2 kVA
MCQ 7
Cores of large power transformers are made from which one of the 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 3
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following ?
(A) Hot-rolled steel
(B) Cold-rolled non-grain oriented steel
(C) Cold-rolled grain oriented steel
(D) Ferrite
MCQ 8
A transformer has a percentage resistance of 2% and percentage 
reactance of 4%. What are its regulations at power factor 0.8 lagging 
and 0.8 leading, respectively ?
(A) 4% and 0.8% -
(B) 3.2% and 1.6% -
(C) 1.6% and 3.2% -
(D) 4.8% and 0.6% -
MCQ 9
The full-load copper loss and iron loss of a transformer are 6400 W 
and 5000 W, respectively. What are the above copper loss and iron 
loss, respectively at half-load ?
(A) 3200 W, 2500 W
(B) 3200 W, 5000 W
(C) 1600 W, 1250 W
(D) 1600 W, 5000 W
MCQ 10
Assertion (A) : A d.c motor draws high current at the time of starting.
Reason (R) : While starting a d.c. motor, it takes some time to 
develop a non-zero value of back e.m.f.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 11
Assertion (A) : For a 3-phase alternator operating on leading p.f. at 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 4
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full load, the terminal voltage may be more than the no-load induced 
e.m.f.
Reason (R) : At leading power factor, the effect of armature reaction 
is demagnetizing.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 12
Assertion (A) : AC armature windings are short chorded by selecting 
value of coil span more than the pole pitch.
Reason (R) : Short chording is done to eliminate harmonics in the 
induced e.m.f.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 13
Assertion (A) : The leakage reactance of a 3-phase induction motor 
should be small.
Reason (R) : A small value of leakage reactance will increase the 
maximum power output of motor.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 14
Assertion (A) : Both the efficiency and regulation of a 3-winding 
ideal transformer are 100%.
Reason (R) : The flux leakage and the magnetic reluctance of the 
magnetic core in an ideal transformer are zero. Moreover, losses are 
absent in ideal transformers.
Page 5


IES Electrical Engineering Topic wise Questions
Electrical Machines
www.gatehelp.com
YEAR 2008
MCQ 1
Consider the following statements:
Skewing of rotors slots in a 3-phase induction motor (cage rotor) may
1. introduce additional leakage reactance
2. eliminate slot harmonics
Which of the statements given above is/are correct ?
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
MCQ 2
In the equivalent circuit of a double-cage induction motor, the two 
rotor cages can be considered
(A) to be in parallel
(B) to be in series-parallel
(C) to be in series
(D) to be in parallel with stator
MCQ 3
A 3-phase squirrel-cage induction motor is started by means of a 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 2
www.gatehelp.com
star/delta switch. What is the starting current of the motor ?
(A) 3 times the current with direct on line starting
(B) 1/3 times the current with direct on line starting
(C) / 13 times the current with direct on line starting
(D) 3 times the current with direct on line starting
MCQ 4
Sludge formation in transformer oil is due to which one of the following 
?
(A) Ingress of duct particles and moisture in the oil
(B) Appearance of small fragments of paper, varnish, cotton and 
other organic materials in the oil
(C) Chemical reaction of transformer oil with the insulating materials
(D) Oxidation of transformer oil
MCQ 5
A single-phase transformer rated for 220/440 V, 50 Hz operates at 
no load at 220 V, 40 Hz. This frequency operation at rated voltage 
results in which one of the following ?
(A) Increase of both eddy-current and hysteresis losses
(B) Reduction of both eddy-current and hysteresis losses
(C) Reduction of hysteresis loss and increase in eddy-current loss
(D) Increase of hysteresis loss and no change in the eddy-current loss
MCQ 6
What is the load at which maximum efficiency occurs in case of a 100 
kVA transformer with iron loss of 1 kW and full-load copper loss of 
2 kW ?
(A) 100 kVA
(B) 70.7 kVA
(C) 50.5 kVA
(D) 25.2 kVA
MCQ 7
Cores of large power transformers are made from which one of the 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 3
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following ?
(A) Hot-rolled steel
(B) Cold-rolled non-grain oriented steel
(C) Cold-rolled grain oriented steel
(D) Ferrite
MCQ 8
A transformer has a percentage resistance of 2% and percentage 
reactance of 4%. What are its regulations at power factor 0.8 lagging 
and 0.8 leading, respectively ?
(A) 4% and 0.8% -
(B) 3.2% and 1.6% -
(C) 1.6% and 3.2% -
(D) 4.8% and 0.6% -
MCQ 9
The full-load copper loss and iron loss of a transformer are 6400 W 
and 5000 W, respectively. What are the above copper loss and iron 
loss, respectively at half-load ?
(A) 3200 W, 2500 W
(B) 3200 W, 5000 W
(C) 1600 W, 1250 W
(D) 1600 W, 5000 W
MCQ 10
Assertion (A) : A d.c motor draws high current at the time of starting.
Reason (R) : While starting a d.c. motor, it takes some time to 
develop a non-zero value of back e.m.f.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 11
Assertion (A) : For a 3-phase alternator operating on leading p.f. at 
IES EE Topic wise 2001-2008 
Electrical Machines
Page 4
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full load, the terminal voltage may be more than the no-load induced 
e.m.f.
Reason (R) : At leading power factor, the effect of armature reaction 
is demagnetizing.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 12
Assertion (A) : AC armature windings are short chorded by selecting 
value of coil span more than the pole pitch.
Reason (R) : Short chording is done to eliminate harmonics in the 
induced e.m.f.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 13
Assertion (A) : The leakage reactance of a 3-phase induction motor 
should be small.
Reason (R) : A small value of leakage reactance will increase the 
maximum power output of motor.
(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 14
Assertion (A) : Both the efficiency and regulation of a 3-winding 
ideal transformer are 100%.
Reason (R) : The flux leakage and the magnetic reluctance of the 
magnetic core in an ideal transformer are zero. Moreover, losses are 
absent in ideal transformers.
IES EE Topic wise 2001-2008 
Electrical Machines
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(A) Both A and R are true and R is the correct explanation of A
(B) Both A and R are true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
MCQ 15
The graph shown below represents which characteristic of a d.c. shunt 
generator ?
(A) Internal characteristic
(B) External characteristic
(C) Open-circuit characteristic
(D) Magnetic characteristic
MCQ 16
When is the mechanical power developed by a d.c. motor maximum ?
(A) Back e.m.f. is equal to applied voltage
(B) Back e.m.f. is equal to zero
(C) Back e.m.f. is equal to half the applied voltage
(D) None of the above
MCQ 17
Match List I (DC machine quantity) with List II (Relation) and 
select the correct answer using the code given below the lists :
List I List II
A. Developed power 1. N af
B. Torque 2. EI
ba
a