DC Generator MCQ Questions and Answers for Practice

1. In a four-pole D.C. machine

1. all the four poles are north poles
2. alternate poles are north and south
3. all the four poles are south poles
4. two north poles follow two south poles

2. In over compounded generator, full load terminal voltage is

1. almost zero
2. less than noload terminal voltage
3. more than noload terminal voltage
4. equal to no-load terminal voltage

3. Armature coil is short circuited by brushes when it lies

1. along neutral axis
2. along field axis
3. in any of the above positions
4. in none of the above positions

4. Lap winding is composed of

1. any even number of conductors
2. any odd number of conductors
3. that even number which is exact multiple of poles + 2
4. that even number which is exact multiple of poles

5. Wave winding is composed of

1. any even number of conductors
2. any odd number of conductors
3. that even number which is exact multiple of poles + 2
4. that even number which is exact multiple of poles

6. The terminal voltage of a D.C. shunt generator drops on load because of all of thefollowing reasons except

1. armature reaction
2. armature resistance drop
3. field weakening due to armature reaction and armature
4. commutation

7. The bearings used to support the rotor shafts are generally

1. ball bearings
2. bush bearings
3. magnetic bearmgs
4. needle bearings

8. In a D.C. generator the critical resistance refers to the resistance of

1. brushes
2. field
3. armature
4. load

9. Brushes of D.C. machines are made of

1. carbon
2. soft copper
3. hard copper
4. all of above

10. Laminations of core are generally made of

1. case iron
2. carbon
3. silicon steel
4. stainless steel

11. In D.C. generators, current to the external circuit from armature is given through

1. commutator
2. solid connection
3. slip rings
4. none of above

12. Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ?

1. 0.005 mm
2. 0.05 mm
3. 0.5 m
4. 5 m

13. Which of the following statement about D.C. generators is false ?

1. Compensating winding in a D.C. machine helps in commutation
2. In a D. C. generator interpoles winding is connected in series with the armaturewinding
3. Back pitch and front pitch are both odd and approximately equal to the pole pitch
4. Equilizing bus bars are used with parallel running of D.C. shunt generators

14. In a commutator

1. copper is harder than mica
2. mica and copper are equally hard
3. mica is harder than copper
4. none of the above

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

1. copper lugs
2. resistance wires
3. insulation pads
4. brazing