DC Generators Mcqs - Set 2

1)   Iron losses in a D.C. machine are independent of variations in______________?

a. speed
b. load
c. voltage
d. speed and voltage
Answer  Explanation 

ANSWER: load

Explanation:
No explanation is available for this question!


2)   In D.C. generators, current to the external circuit from armature is given through_____________?

a. commutator
b. solid connection
c. slip rings
d. none of above
Answer  Explanation 

ANSWER: commutator

Explanation:
No explanation is available for this question!


3)   Brushes of D.C. machines are made of_________?

a. carbon
b. soft copper
c. hard copper
d. all of above
Answer  Explanation 

ANSWER: carbon

Explanation:
No explanation is available for this question!


4)   If a D.C. generator fails to build up the probable cause could not be_____________?

a. imperfect brush contact
b. field resistance less than the critical resistance
c. no residual magnetism in the generator
d. faulty shunt connections tending to reduce the residual magnetism
Answer  Explanation 

ANSWER: field resistance less than the critical resistance

Explanation:
No explanation is available for this question!


5)   If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by______________?

a. Blv
b. Blv2
c. Bl2v
d. Bl2v2
Answer  Explanation 

ANSWER: Blv

Explanation:
No explanation is available for this question!


6)   In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be__________________?

a. 4
b. 8
c. 16
d. 32
Answer  Explanation 

ANSWER: 8

Explanation:
No explanation is available for this question!


7)   The material for commutator brushes is generally_______________?

a. mica
b. copper
c. cast iron
d. carbon
Answer  Explanation 

ANSWER: carbon

Explanation:
No explanation is available for this question!


8)   The insulating material used between the commutator segments is normally_____________?

a. graphite
b. paper
c. mica
d. insulating varnish
Answer  Explanation 

ANSWER: mica

Explanation:
No explanation is available for this question!


9)   In D.C. generators, the brushes on commutator remain in contact with conductors which_________________?

a. lie under south pole
b. lie under north pole
c. lie under interpolar region
d. are farthest from the poles
Answer  Explanation 

ANSWER: lie under interpolar region

Explanation:
No explanation is available for this question!


10)   If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be________________?

a. demagnetisation only
b. cross magnetisation as well as mag¬netisation
c. crossmagnetisation as well as demagnetising
d. cross magnetisation only
Answer  Explanation 

ANSWER: crossmagnetisation as well as demagnetising

Explanation:
No explanation is available for this question!


11)   Armature reaction of an unsaturated D.C. machine is_____________?

a. crossmagnetising
b. demagnetising
c. magnetising
d. none of above
Answer  Explanation 

ANSWER: crossmagnetising

Explanation:
No explanation is available for this question!


12)   D.C. generators are connected to the busbars or disconnected from them only under the floating condition________________?

a. to avoid sudden loading of the primemover
b. to avoid mechanicaljerk to the shaft
c. to avoid burning of switch contacts
d. all above
Answer  Explanation 

ANSWER: all above

Explanation:
No explanation is available for this question!


13)   Eddy currents are induced in the pole shoes of a D.C. machine due to______________?

a. oscillating magnetic field
b. pulsating magnetic flux
c. relative rotation between field and armature
d. all above
Answer  Explanation 

ANSWER: relative rotation between field and armature

Explanation:
No explanation is available for this question!


14)   Equilizer rings are required in case armature is_______________?

a. wave wound
b. lap wound
c. delta wound
d. duplex wound
Answer  Explanation 

ANSWER: lap wound

Explanation:
No explanation is available for this question!


15)   Welding generator will have____________?

a. lap winding
b. wave winding
c. delta winding
d. duplex wave winding
Answer  Explanation 

ANSWER: lap winding

Explanation:
No explanation is available for this question!


16)   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
Answer  Explanation 

ANSWER: number of armature coils

Explanation:
No explanation is available for this question!


17)   For a D.C. machines laboratory following type of D.C. supply will be suitable___________?

a. rotary converter
b. mercury are rectifier
c. induction motor D.C. generator set
d. synchronous motor D.C. generator set
Answer  Explanation 

ANSWER: induction motor D.C. generator set

Explanation:
No explanation is available for this question!


18)   Flashing the field of D.C. generator means:______________?

a. neutralising residual magnetism
b. creating residual magnetism by a D.C. source
c. making the magnetic losses of forces parallel
d. increasing flux density by adding extra turns of windings on poles
Answer  Explanation 

ANSWER: creating residual magnetism by a D.C. source

Explanation:
No explanation is available for this question!


19)   The function of pole shoes in the case of D.C. machine is______________?

a. to reduce the reluctance of the mag¬netic path
b. to spread out the flux to achieve uniform flux density
c. to support the field coil
d. to discharge all the above functions
Answer  Explanation 

ANSWER: to discharge all the above functions

Explanation:
No explanation is available for this question!


20)   In the case of lap winding resultant pitch is____________?

a. multiplication of front and back pitches
b. division of front pitch by back pitch
c. sum of front and back pitches
d. difference of front and back pitches
Answer  Explanation 

ANSWER: difference of front and back pitches

Explanation:
No explanation is available for this question!