Question 1

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

Accepted Answer

A) severe sparking 
B) rough commutator surface 
C) imperfect contact 
D) All of the above 
A) severe sparking 
B) rough commutator surface 
C) imperfect contact 
D) All of the above D

Question 2

In lap winding, the number of brushes is always

Accepted Answer

A) double the number of poles 
B) same as the number of poles 
C) half the number of poles 
D) two 
A) double the number of poles 
B) same as the number of poles 
C) half the number of poles 
D) two B

Question 3

The resistance of armature winding depends on

Accepted Answer

A) length of conductor 
B) cross-sectional area of the conductor 
C) number of conductors 
D) all of the above 
A) length of conductor 
B) cross-sectional area of the conductor 
C) number of conductors 
D) all of the above D

Question 4

Copper brushes in D.C. machine are used

Accepted Answer

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 
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

Question 5

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

Accepted Answer

A) 4 
B) 8 
C) 16 
D) 32 
A) 4 
B) 8 
C) 16 
D) 32

Question 6

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

Accepted Answer

A) rivets 
B) counter sunk screws 
C) brazing 
D) welding 
A) rivets 
B) counter sunk screws 
C) brazing 
D) welding

Question 7

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. ?

Accepted Answer

A) Lap winding 
B) Wave winding 
C) Either of (a) and (b) above 
D) Depends on other features of design 
A) Lap winding 
B) Wave winding 
C) Either of (a) and (b) above 
D) Depends on other features of design

Question 8

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

Accepted Answer

A) 0.005 mm 
B) 0.05 mm 
C) 0.5 m 
D) 5 m 
A) 0.005 mm 
B) 0.05 mm 
C) 0.5 m 
D) 5 m

Question 9

In the D.C. motor the iron losses occur in

Accepted Answer

A) the field 
B) the armature 
C) the brushes 
D) the commutator 
A) the field 
B) the armature 
C) the brushes 
D) the commutator

Question 10

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

Accepted Answer

A) Blv 
B) Blv2 
C) Bl2v 
D) Bl2v2 
A) Blv 
B) Blv2 
C) Bl2v 
D) Bl2v2

Question 11

In a commutator

Accepted Answer

A) copper is harder than mica 
B) mica and copper are equally hard 
C) mica is harder than copper 
D) none of the above 
A) copper is harder than mica 
B) mica and copper are equally hard 
C) mica is harder than copper 
D) none of the above

Question 12

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

Accepted Answer

A) current 
B) voltage 
C) speed 
D) none of above 
A) current 
B) voltage 
C) speed 
D) none of above

Question 13

Brushes of D.C. machines are made of

Accepted Answer

A) carbon 
B) soft copper 
C) hard copper 
D) all of above 
A) carbon 
B) soft copper 
C) hard copper 
D) all of above

Question 14

While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards

Accepted Answer

A) direction of induced e.m.f. 
B) direction of flux 
C) direction of motion of the conductor if forefinger points in the direction of generated e.m.f. 
D) direction of motion of conductor, if forefinger points along the lines of flux 
A) direction of induced e.m.f. 
B) direction of flux 
C) direction of motion of the conductor if forefinger points in the direction of generated e.m.f. 
D) direction of motion of conductor, if forefinger points along the lines of flux

Question 15

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

Accepted Answer

A) copper lugs 
B) resistance wires 
C) insulation pads 
D) brazing 
A) copper lugs 
B) resistance wires 
C) insulation pads 
D) brazing

Question 16

Satisfactory commutation of D.C. machines requires

Accepted Answer

A) brushes should be of proper grade and size 
B) brushes should smoothly run in the holders 
C) smooth, concentric commutator properly undercut 
D) all of the above 
A) brushes should be of proper grade and size 
B) brushes should smoothly run in the holders 
C) smooth, concentric commutator properly undercut 
D) all of the above

Question 17

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

Accepted Answer

A) commutator 
B) solid connection 
C) slip rings 
D) none of above 
A) commutator 
B) solid connection 
C) slip rings 
D) none of above

Question 18

The bearings used to support the rotor shafts are generally

Accepted Answer

A) ball bearings 
B) bush bearings 
C) magnetic bearmgs 
D) needle bearings 
A) ball bearings 
B) bush bearings 
C) magnetic bearmgs 
D) needle bearings

Question 19

A separately excited generator as compared to a self-excited generator

Accepted Answer

A) is amenable to better voltage con-trol 
B) is more stable 
C) has exciting current independent of load current 
D) has all above features 
A) is amenable to better voltage con-trol 
B) is more stable 
C) has exciting current independent of load current 
D) has all above features

Question 20

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

Accepted Answer

A) mica 
B) copper 
C) cast iron 
D) carbon 
A) mica 
B) copper 
C) cast iron 
D) carbon

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

In lap winding, the number of brushes is always

The resistance of armature winding depends on

Copper brushes in D.C. machine are used

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

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

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. ?

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

In the D.C. motor the iron losses occur in

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

In a commutator

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

Brushes of D.C. machines are made of

While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards

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

Satisfactory commutation of D.C. machines requires

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

The bearings used to support the rotor shafts are generally

A separately excited generator as compared to a self-excited generator

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

Transformer Fundamentals and Operation

Transformer Technology and Design

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Transformers: Efficiency, Design, and Testing

Transformers: Voltage Regulation, Efficiency, and Protection

Transformer and D.C Motor

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D.C Motors and Speed Control

D.C Motors and Controls

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D.C Generators and Commutators

D.C Generator Operation and Construction

D.C Generators

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Exam 11: D.C Machine and Generator Laminations, Commutation, and Components

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

In lap winding, the number of brushes is always

The resistance of armature winding depends on

Copper brushes in D.C. machine are used

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

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

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. ?

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

In the D.C. motor the iron losses occur in

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

In a commutator

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

Brushes of D.C. machines are made of

While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards

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

Satisfactory commutation of D.C. machines requires

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

The bearings used to support the rotor shafts are generally

A separately excited generator as compared to a self-excited generator

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

Transformer Fundamentals and Operation

Transformer Technology and Design

Transformer: Resistance, Oil, Relays, Harmonics, and Core Properties

Transformers: Efficiency, Design, and Testing

Transformers: Voltage Regulation, Efficiency, and Protection

Transformer and D.C Motor

D.C Motors and Starters

D.C Motors and Speed Control

D.C Motors and Controls

D.C Motors and Generators

D.C Generators and Commutators

D.C Generator Operation and Construction

D.C Generators

Direct Current Generators and Parallel Operation

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