DC GENERATOR OBJECTIVE QUESTION WITH EXPLANATION : 01 to 40

DC GENERATOR OBJECTIVE QUESTION WITH EXPLANATION : 01 to 40

Q no 1 . Which of the following could be lamina proximately the thickness of laminations of a D.C .                 machine ?

              a ) 0.005 mm      b ) 0.05 mm     c ) 0.5 mm     d ) 5 mm
 explanations
                        correct answer ; ( C ) 0.5 mm 

Q no 2 . While applying fleming 's right hand rule to find the direction of induced emf , the thumb                      points towards :

 a ) direction of induced emf        
 b ) direction of flux

 c ) direction of motion of the conductor if forefinger points in the direction of generated emf
 d )  direction of motion of the conductor if forefinger points along the lines of flux

 correct answer :  d )  direction of motion of the conductor if forefinger points along the lines of flux

Q no 3. Copper brushes in D.C machine are used

A ) where low voltage and high currents are involved

B ) where high voltage and Small currents are involved

C ) in both of the above case

D ) in none of the above case

explanations
                    answer A ) where low voltage and high currents are involved

Q no 4 . Iron losses in a D.C machine are independent of variations in

A ) speed

B ) load

C ) voltage

D ) speed and voltage

explanations
                    answer b )load

Q no 5. In case of D.C machine winding , number of commutator segments is equal to

A ) number of armature coils

B ) number of armature coil sides

C ) number of armature conductors

D ) number of armature turns

explanations
                    answer A ) number of armature coils

Q no 6. Which of the following statement above D.C generator is false ?

A ) compensating winding in a D.C machine helps in commutation

B ) in a D.C generator intercooled winding is connected in series with the armature winding

C ) back pitch and front pitch are both odd and approximately equal to pole pitch 

D ) Equalizing bus bars are used with parallel running of D.C shunt generator

explanations
                    answer D ) Equalizing bus bars are used with parallel running of D.C shunt generator

Q no 7. The demagnetising components of armature reaction in a D.C generator

A ) reduces generator e.m.f

B ) increase armature speed

C ) reduces Interpoles flux density

D ) results in sparking trouble

explanations
                    answer A ) reduces generator e.m.f

Q no 8. The e.m.f generated by a shunt wound D.C generator is E . now while pole flux remains constant ., If the speed of generator is doubled , the e.m.f generated will be 

A ) E/2

B ) 2 E

C ) slightly less than E

D ) E

explanations
                    answer B ) 2 E

Q no 9. In a shunt generator the voltage build up is generally restricted by 

A ) speed limitations 

B ) armature heating

C ) insulation restrictions
D ) saturation of iron

explanations
                    answer D ) saturation of iron

Q no 10. Number of tappings for each Equilizer  ring is  equal to 

A ) number of pole pairs

B ) number of poles 

C ) number of parallel paths

D ) number of commutator segments
explanations
                    answer A ) number of pole pairs

 no 11. Lap winding is composed of 

       a ) any even number of conductor

       b ) any odd number of conductor

       c ) that even number which is exact multiple of poles +2

       d ) that even number which is exact multiple of poles

explanations

                 answer a ) any even number of conductor

Q no 12. wave winding is composed of
       a ) any even number of conductor
       b ) any odd number of conductor
       c ) that even number which is exact multiple of poles +2
       d ) that even number which is exact multiple of poles
explanations
                 answer c ) that even number which is exact multiple of poles +2

Q no 13. In case of flat compound generator

A ) voltage generated is less than the rated voltage

B ) generated voltage is proportional to the load on the generator

C ) voltage remain constant irrespective of the load

D ) speed varies in proportional to the load on the generator

Q no 14. The terminal voltage of DC shunt generator drop on load because of all of the following reasons except

A ) armature reaction

B ) armature resistance drop

C ) field weakening due to armature reaction and armature

D ) commutation

Q no 15. If residual magnetism is present in a DC generator , the induced emf at zero speed will be 

A ) zero

B ) small

C ) the same as rated voltage

D ) high

Q no 16. Following energized winding of DC machine should not be opened as it would produce high inductive voltage which may be dangerous to personal and may cause to own insulation failure. 

A ) series field

B ) compensating winding

C ) inter pole field

D ) shunt field

Q no 17. Two generator are running in parallel . One of the generator may run as motor​ for which of the following reasons ?

A ) the direction of the generator is reversed

B ) the speed of the generator is increased

C ) the field of the generator is weakened

D ) that generator take large share of the load 

Q no 18. A series generator can be self excite 

A ) only if the load current is zero

B ) only if the load current is not zero

C ) irrespective of the value of the load current

D ) none of the above

Q no 19. A shunt generator can be self excite

A ) only if the resistance of the field circuit is less than critical value

B ) only if the resistance of the field circuit is greater than critical value

C ) irrespective of the value of the resistance in the field circuit

 

Q no 20. The terminal voltage of a series generator is 150 V when the load current is 5 A . If the load current is increased to 10 A , the terminal voltage will be 

A ) 150 V

B ) less than 150 V 

C ) greater than 150 V 

D ) none of the above

Q no 21. Which generator would you prefer for feeding long DC transmission line ?
A ) series generator
B ) shunt generator
C ) over compound generator
D ) flat compound generator

Q no 22. In DC generator the critical resistance can be increased by
A ) increasing its field resistance
B ) decreasing its field resistance
C ) increasing its speed
D ) decreasing its speed

Q no 23. For both lap and wave winding , there are so many commutator bars as the number of
A ) slots
B ) armature conductor
C ) winding elements
D ) poles

Q no 24. The series field of a short shunt DC generator is excited by
A ) external current
B ) armature current
C ) shunt current
D ) load current

Q no 25. If a self excited​ DC generator after being installed , fails to build up on its first trial run , the first thing to do is to
A ) reverse the field connection
B ) increase the field resistance
C ) increase the speed of prime mover
D )  check armature insulation resistance

Q no 26 . The slight curvature at the lower end of the O.C.C to f a self excited DC generator is due​ to
A ) high armature speed
B ) high field circuit resistance
C ) residual pole flux
D ) magnetic inertia
E ) none of the above

Q no 27. Which of the following types of generator does not need  equilizers for satisfactory  parallel operation ?
A ) flat compound
B ) over compound
C ) under compound
D ) series

Q no 28. The ........ generator has poorest voltage regulation .
A ) shunt
B ) series
C ) compound
D ) over compound

Q no 29. Which of the following generator is used for charging the battery ?
A ) shunt
B ) series
C ) compound
D ) any of the above

Q no 30. An external resistance added in the field of a DC shunt generator will
A ) decrease the voltage of the generator
B ) increase the voltage of the generator
C ) increase the power delivered
D ) increase the speed of the generator
D ) decrease the speed of the generator

Q no 31. Which of the following statement is incorrect in DC shunt generator about hysteresis loss?
A ) it is independent of lamination thickness
B ) it can be minimize by lamination the armature
C ) it depends on supply frequency
D ) none of the above

Q no 32. Which generator cannot start if there is no residual magnetism ?
A ) series generator
B ) shunt generator
C ) separately excited generator
D ) all of the above

Q no 33. Drop in speed of a DC generator due to increase in load can be compensated by
A ) cooling the armature
B ) increasing the armature resistance
C ) reducing the load voltage
D ) increasing the input to the prime mover