dcmachines.docx

8/12/2019 dcmachines.docx

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1. The output power of any electrical motor is taken from the:

a) Armature

b) Field

c) Coupling mounted on the shaft

d) Motor frame

C

2. If the back emf in a dc motor varnishes suddenly, then the motor:

a) Run at very high speeds

b) Start hunting

c) Burn

d) Come to stall

C

3. The direction of the armature current in a dc motor is: a) The same as the generated emf

b) Opposite to that of generated emf

c) Not dependent upon the direction of the armature emf

d) None of the above

B

4. When a dc machine is connected to the dc supply main it will produce:

a) EMF in opposition to the applied voltage

b) EMF in phase with the applied voltage

c) EMF decreases with time


A

5. The direction of rotation of a dc motor can be determined by:

a) Fleming's right hand rule

b) Fleming's left hand rule

c) Lenz's law

d) Ampere's law

B

6. A thick wire is used in dc series motor field winding than that in dc shunt motor:

a) To create more flux


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b) To reduce the resistance

c) To carry large load current

d) Both (b) and (c)

D

7. An electrical train employing a dc series motor is running at the fixed speed, when a

sudden slight drop in the mains voltage occurs. This would result in:

a) Drop in the speed and rise in the current

b) Rise in the speed and drop in the current

c) Rise in the speed and rise in the current

d) Drop in speed with current unaltered

A

8. A DC shunt motor is driving a constant torque load. On inserting an additional

resistance in the armature circuit, the speed of the motor will:

a) Remains unchanged

b) Increases

c) Decreases

d) Be Zero

C

9. A DC series motor is best suited for electrical traction because:a) It develops high starting torque

b) It runs at very high speed

c) It is cheaper in cost

d) It is more rugged in construction like induction motor

A

10. A DC series motor is used for overhauling load. It can work stable if:

a) The armature is shunted by a resistor

b) The field winding is revered

c) A resistor is put in series with the machine

d) A divertor is put across the field

A

11. Which of the following dc motor has maximum self relieving property:


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a) Shunt

b) Series

c) Cumulative compound

d) Differential compound

B

12. When the direction of power flow in a differential compounded motor reverses, it will

operate as a:

a) Cumulative compound generator

b) Differential compound generator

c) Series motor

d) Shunt motor

A

13. A separately excited dc generator is feeding dc shunt motor. If the load torque on

the motor is halved approximately, then:

a) Armature current of both motor and generator are halved

b) Armature current of motor is halved and that of the generator is unaltered

c) Armature current of generator is halved and that of the motor is unaltered

d) Armature current of both motor and generator are unaltered

A

14. A flywheel is employed with a dc compound motor to reduce the peak demand, the

compound motor should be:

a) Level compound

b) Differential compound



C

15. The flux leakage coefficient in dc machine is usually:

a) 0.6 to 0.8

b) 1.05

c) 1.1 to 1.3

d) 2 to 2.5

C


4/21

DC Machines Test Questions Answers1. The output power of any electrical motor is taken from the:a) Armatureb) Fieldc) Coupling mounted on the shaft

d) Motor frame

C

2. If the back emf in a dc motor varnishes suddenly, then the motor: a) Run at very high speedsb) Start huntingc) Burnd) Come to stall

C

3. The direction of the armature current in a dc motor is:a) The same as the generated emfb) Opposite to that of generated emfc) Not dependent upon the direction of the armature emfd) None of the above

B

4. When a dc machine is connected to the dc supply main it will produce: a) EMF in opposition to the applied voltageb) EMF in phase with the applied voltagec) EMF decreases with timed) None of the above

A

5. The direction of rotation of a dc motor can be determined by: a) Fleming's right hand ruleb) Fleming's left hand rulec) Lenz's lawd) Ampere's law

B

6. A thick wire is used in dc series motor field winding than that in dc shunt motor: a) To create more fluxb) To reduce the resistancec) To carry large load current
http://electricalobjectivetestquestions.blogspot.in/2013/02/dc-machines-test-questions-answers.htmlhttp://electricalobjectivetestquestions.blogspot.in/2013/02/dc-machines-test-questions-answers.html


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d) Both (b) and (c)

D


sudden slight drop in the mains voltage occurs. This would result in:a) Drop in the speed and rise in the currentb) Rise in the speed and drop in the currentc) Rise in the speed and rise in the currentd) Drop in speed with current unaltered

A

8. A DC shunt motor is driving a constant torque load. On inserting an additionalresistance in the armature circuit, the speed of the motor will:a) Remains unchanged

b) Increasesc) Decreasesd) Be Zero

C

9. A DC series motor is best suited for electrical traction because:a) It develops high starting torqueb) It runs at very high speedc) It is cheaper in costd) It is more rugged in construction like induction motor

A

10. A DC series motor is used for overhauling load. It can work stable if: a) The armature is shunted by a resistorb) The field winding is reveredc) A resistor is put in series with the machine d) A divertor is put across the field

A

11. Which of the following dc motor has maximum self relieving property:a) Shuntb) Seriesc) Cumulative compoundd) Differential compound

B


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12. When the direction of power flow in a differential compounded motor reverses, it willoperate as a:a) Cumulative compound generatorb) Differential compound generatorc) Series motor

d) Shunt motor

A

13. A separately excited dc generator is feeding dc shunt motor. If the load torque onthe motor is halved approximately, then:a) Armature current of both motor and generator are halvedb) Armature current of motor is halved and that of the generator is unalteredc) Armature current of generator is halved and that of the motor is unalteredd) Armature current of both motor and generator are unaltered

A

14. A flywheel is employed with a dc compound motor to reduce the peak demand, thecompound motor should be:a) Level compoundb) Differential compoundc) Cumulative compoundd) None of the above

C

15. The flux leakage coefficient in dc machine is usually:a) 0.6 to 0.8b) 1.05c) 1.1 to 1.3d) 2 to 2.5

C


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a) Armature

b) Field


d) Motor frame

C



b) Start hunting

c) Burn

d) Come to stall

C

3. The direction of the armature current in a dc motor is:

a) The same as the generated emf




B

4. When a dc machine is connected to the dc supply main it will produce: a) EMF in opposition to the applied voltage




A




c) Lenz's law

d) Ampere's law

B



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d) Both (b) and (c)

D







A




b) Increases

c) Decreases

d) Be Zero

C

9. A DC series motor is best suited for electrical traction because:

a) It develops high starting torque




A






A


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a) Shunt

b) Series



B


operate as a:



c) Series motor

d) Shunt motor

A







A



a) Level compound




C


a) 0.6 to 0.8

b) 1.05

c) 1.1 to 1.3

d) 2 to 2.5

C


10/21

DC Machines Test Questions Answers1. The output power of any electrical motor is taken from the:a) Armature

b) Fieldc) Coupling mounted on the shaftd) Motor frame

C

2. If the back emf in a dc motor varnishes suddenly, then the motor: a) Run at very high speedsb) Start huntingc) Burnd) Come to stall

C

3. The direction of the armature current in a dc motor is: a) The same as the generated emfb) Opposite to that of generated emfc) Not dependent upon the direction of the armature emfd) None of the above

B

4. When a dc machine is connected to the dc supply main it will produce: a) EMF in opposition to the applied voltageb) EMF in phase with the applied voltagec) EMF decreases with timed) None of the above

A

5. The direction of rotation of a dc motor can be determined by: a) Fleming's right hand ruleb) Fleming's left hand rule

c) Lenz's lawd) Ampere's law

B

6. A thick wire is used in dc series motor field winding than that in dc shunt motor: a) To create more fluxb) To reduce the resistance


11/21

c) To carry large load currentd) Both (b) and (c)

D

7. An electrical train employing a dc series motor is running at the fixed speed, when asudden slight drop in the mains voltage occurs. This would result in:a) Drop in the speed and rise in the currentb) Rise in the speed and drop in the currentc) Rise in the speed and rise in the currentd) Drop in speed with current unaltered

A

8. A DC shunt motor is driving a constant torque load. On inserting an additionalresistance in the armature circuit, the speed of the motor will:

a) Remains unchangedb) Increasesc) Decreasesd) Be Zero

C

9. A DC series motor is best suited for electrical traction because:a) It develops high starting torqueb) It runs at very high speedc) It is cheaper in cost


A

10. A DC series motor is used for overhauling load. It can work stable if: a) The armature is shunted by a resistorb) The field winding is reveredc) A resistor is put in series with the machine d) A divertor is put across the field

A

11. Which of the following dc motor has maximum self relieving property:a) Shuntb) Seriesc) Cumulative compoundd) Differential compound

B


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12. When the direction of power flow in a differential compounded motor reverses, it willoperate as a:a) Cumulative compound generatorb) Differential compound generator

c) Series motord) Shunt motor

A

13. A separately excited dc generator is feeding dc shunt motor. If the load torque onthe motor is halved approximately, then:a) Armature current of both motor and generator are halvedb) Armature current of motor is halved and that of the generator is unalteredc) Armature current of generator is halved and that of the motor is unalteredd) Armature current of both motor and generator are unaltered

A

14. A flywheel is employed with a dc compound motor to reduce the peak demand, thecompound motor should be:a) Level compoundb) Differential compoundc) Cumulative compoundd) None of the above

C

15. The flux leakage coefficient in dc machine is usually:a) 0.6 to 0.8b) 1.05c) 1.1 to 1.3d) 2 to 2.5

C


13/21

TUESDAY, FEBRUARY 5, 2013

DC Machines Test Questions Answers1. The output power of any electrical motor is taken from the:

a) Armature

b) Field


d) Motor frame

C



b) Start hunting

c) Burn

d) Come to stall

C






B


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4. When a dc machine is connected to the dc supply main it will produce:

a) EMF in opposition to the applied voltage




A




c) Lenz's law

d) Ampere's law

B





d) Both (b) and (c)

D

7. An electrical train employing a dc series motor is running at the fixed speed, when a sudden

slight drop in the mains voltage occurs. This would result in:


15/21





A

8. A DC shunt motor is driving a constant torque load. On inserting an additional resistance in

the armature circuit, the speed of the motor will:


b) Increases

c) Decreases

d) Be Zero

C






A




16/21




A


a) Shunt

b) Series



B

12. When the direction of power flow in a differential compounded motor reverses, it will operate

as a:



c) Series motor

d) Shunt motor

A

13. A separately excited dc generator is feeding dc shunt motor. If the load torque on the motor

is halved approximately, then:




17/21



A



a) Level compound




C


a) 0.6 to 0.8

b) 1.05

c) 1.1 to 1.3

d) 2 to 2.5

C


18/21


a) Armature

b) Field


d) Motor frame

C



b) Start hunting

c) Burn

d) Come to stall

C






B

4. When a dc machine is connected to the dc supply main it will produce: a) EMF in opposition to the applied voltage




A




c) Lenz's law

d) Ampere's law

B



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d) Both (b) and (c)

D







A




b) Increases

c) Decreases

d) Be Zero

C






A






A


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a) Shunt

b) Series



B


operate as a:



c) Series motor

d) Shunt motor

A







A



a) Level compound




C


a) 0.6 to 0.8

b) 1.05

c) 1.1 to 1.3

d) 2 to 2.5

C


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