DC Machines MCQs | DC Generator MCQs Questions& Answers | Electrical Engineering MCQs Quiz|

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in this article you will find the most important MCQs related to DC MACHNES i.e. Dc Generator.

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DC MACHINE MOST IMPORTANT MCQ | ELECTRICAL MACHINES | ELECTRICAL ENGINEERING MCQ |

1. The resistance of armature winding depends on ?

(a) length of conductor
(b) cross-sectional area of the conductor
(c) number of conductors
(d) all of the above

... Answer is (d)
(d) all of the above

2. The armature of D.C. generator is laminated to

(a) reduce the bulk
(b) provide the bulk
(c) insulate the core
(d) reduce eddy current loss

... Answer is (d)
(d) reduce eddy current loss

3. 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 m
(d) 5 m

... Answer is (c)
0.5 mm

4. Laminations of core are generally made of ?

(a) case iron
(b) carbon
(c) silicon steel
(d) stainless steel

... Answer is (c)
silicon steel

5. The field coils of D.C. generator are usually made of ?

(a) mica
(b) copper
(c) cast iron
(d) carbon

... Answer is (b)
copper

6. The commutator segments are connected to the armature conductors by means of ?

(a) copper lugs
(b) resistance wires
(c) insulation pads
(d) brazing

... Answer is (a)
(a) copper lugs

7. In a commutator ?

(a) copper is harder than mica
(b) mica and copper are equally hard
(c) mica is harder than copper
(d) none of the above

... Answer is (c)
mica is harder than copper

8. In D.C. generators the pole shoes are fastened to the pole core by ?

(a) rivets
(b) counter sunk screws
(c) brazing
(d) welding

... Answer is (b)
(b) counter sunk screws

9. According to Fleming's right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of ?

(a) motion of conductor
(b) lines of force
(c) either of the above
(d) none of the above

... Answer is (b)
(b) lines of force

10. . Fleming's right-hand rule regarding direction of induced e.m.f., correlates ?

(a) magnetic flux, direction of current flow and resultant force
(b) magnetic flux, direction of motion and the direction of e.m.f. induced
(c) magnetic field strength, induced voltage and current
(d) magnetic flux, direction of force and direction of motion of conductor

... Answer is (b)
(b) magnetic flux, direction of motion and the direction of e.m.f. induced

11.The bearings used to support the rotor shafts are generally ?

(a) ball bearings
(b) bush bearings
(c) magnetic bearmgs
(d) needle bearings

... Answer is (a)
(a) ball bearings

12. In D.C. generators, the cause of rapid brush wear may be ?

(a) severe sparking
(b) rough commutator surface
(c) imperfect contact
(d) any of the above

... Answer is (d)
(d) any of the above

13. . In lap winding, the number of brushes is always ?

(a) double the number of poles
(b) same as the number of poles
(c) half the number of poles
(d) two

... Answer is (b)
(b) same as the number of poles

14. For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

(a) Lap winding
(b) Wave winding
(c) Either of (a) and (b) above
(d) Depends on other features of design

... Answer is (b)
(b) Wave winding

15 In a four-pole D.C. machine ?

(a) all the four poles are north poles
(b) alternate poles are north and south
(c) all the four poles are south poles
(d) two north poles follow two south

... Answer is (b)
(b) alternate poles are north and south

16. Copper brushes in D.C. machine are used ?

(a) where low voltage and high currents are involved

(b) where high voltage and small cur-rents are involved
(c) in both of the above cases
(d) in none of the above cases

... Answer is (a)
(a) where low voltage and high currents are involved

17. A separately excited generator as compared to a self-excited generator ?

(a) is amenable to better voltage control
(b) is more stable
(c) has exciting current independent of load current
(d) has all above features

... Answer is (d)
(d) has all above features

18. . In case of D.C. machines, mechanical losses are primary function of ?

(a) current
(b) voltage
(c) speed
(d) none of above

... Answer is (c)
(c) speed

19. Iron losses in a D.C. machine are independent of variations in ?

(a) speed
(b) load
(c) voltage
(d) speed and voltage

... Answer is (b)
(b) load

20.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 is (a)
(a) commutator

21. Brushes of D.C. machines are made of ?

(a) carbon
(b) soft copper
(c) hard copper
(d) all of above

... Answer is (a)
(a) carbon

22. 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 /label>
(c) 16
(d) 32

... Answer is (b)
8

23. The insulating material used between the commutator segments is normally ?

(a) graphite
(b) paper
(c) mica
(d) insulating varnish

... Answer is (c)
(c) mica

24. . 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 is (c)
(c) lie under interpolar region

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

(a) demagnetization only
(b) cross magnetization as well as magnetization
(c) cross magnetization as well as demagnetizing
(d) cross magnetization only

... Answer is (c)
(c) cross magnetization as well as demagnetizing

26. Armature reaction of an unsaturated D.C. machine is ?

(a) cross magnetizing
(b) demagnetizing
(c) magnetizing
(d) none of above

... Answer is (a)
(a) cross magnetizing

27. D.C. generators are connected to the bus bars or disconnected from them only under the floating condition ?

(a) to avoid sudden loading of the prime mover
(b) to avoid mechanical jerk to the shaft
(c) to avoid burning of switch contacts
(d) all above

... Answer is (d)
(d) all above

28.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 is (c)
(c) relative rotation between field and armature

29. . Equalizer rings are required in case armature is ?

(a) wave wound
(b) lap wound
(c) delta wound
(d) duplex wound

... Answer is (b)
(b) lap wound

30. . Welding generator will have

(a) lap winding
(b) wave winding
(c) delta winding
(d) duplex wave winding

... Answer is (a)
(a) lap winding