Practice D.C. Generators Multiple Choice Questions Quiz-1 - MCQGeeks.com

Q.1

The following constitute short-circuit in the armature winding.

Insulation failure between two commutator bars
Insulation failure between two turns of a coil
Two of more turns of the same coil getting grounded
All of the above

Q.2

In a D.C. generator the actual flux distribution depends upon

size of air gap
shape of the pole shoe
clearance between tips of the adjacent pole shoes
all of the above

Q.3

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

Severe sparking
Rough commutator surface
Imperfect contact
Any of the above

Q.4

The e.m.f. generated by a shunt wound D.C. generator is E. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be

E/2
2E
Slightly less than E
E

Q.5

In the case of lap winding resultant pitch is

Multiplication of front and back pitches
Division of front pitch by back pitch
Sum of front and back pitches
Difference of front and back pitches

Q.6

In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when

r.p.m. is more than 300
r.p.m. is less than 300
Number of poles is 4
Number of poles is 2

Q.7

In a commutator

Copper is harder than mica
Mica and copper are equally hard
Mica is harder than copper
None of the above

Q.8

Armature reaction in a generator results in

Demagnetization of leading pole tip and magnetization of trailing pole tip
Demagnetization of trailing pole tip and magnetization of leading pole tip
Demagnetizing the center of all poles
Magnetizing the center of all poles

Q.9

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

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

Q.10

Following D.C. generator will be in a position to build up without any residual magnetism in the poles

Series generator
Shunt generator
Compound generator
Self-excited generator

Q.11

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

Speed
Load
Voltage
Speed and voltage

Q.12

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.?

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

Q.13

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

Magnetic flux, direction of current flow and resultant force
Magnetic flux, direction of motion and the direction of e.m.f. induced
Magnetic field strength, induced voltage and current
Magnetic flux, direction of force and direction of motion of conductor

Q.14

Compensating windings are used in D.C. generators

Mainly to reduce the eddy currents by providing local short-circuits
To provide path for the circulation of cooling air
To neutralize the cross-magnetizing effect of the armature reaction
None of the above

Q.15

In a shunt generator the voltage build up is generally restricted by

speed limitation
armature heating
insulation restrictions
saturation of iron

Q.16

The series field of a short-shunt D.C. generator is excited by

external current
armature current
shunt current
load current

Q.17

A series generator can self-excite

Only if the load current is zero
Only if the load current is not zero
Irrespective of the value of load current
None of the above

Q.18

The armature of D.C. generator is laminated to

reduce the bulk
provide the bulk
insulate the core
reduce eddy current loss

Q.19

A D.C. generator can be considered as

Rectifier
Prime mover
Rotating amplifier
Power pump

Q.20

In case of a flat compounded generator

Voltage generated is less than the rated voltage
Generated voltage is proportional to the load on the generator
Voltage remains constant irrespective of the load
Speed varies in proportion to the load on the generator

Q.21

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

To avoid sudden loading of the prime mover
To avoid mechanical jerk to the shaft
To avoid burning of switch contacts
All above

Q.22

In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called

rotor
stator
field
armature

Q.23

In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilized is called

Rotor
Stator
Field
Armature

Q.24

Flashing the field of D.C. generator means

Neutralizing residual magnetism
Creating residual magnetism by a D.C. source
Making the magnetic losses of forces parallel
Increasing flux density by adding extra turns of windings on poles

Q.25

In a separately excited generator supplying rated load the armature reaction:

Is always present
Is always absent
May be sometimes present
None of the above

Q.26

A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly

150 V
175 V
240 V
290 V

Q.27

For both lap and wave windings, there are as many commutator bars as the number of

Slots
Armature conductors
Winding elements
Poles

Q.28

D.C. series generator is used

To supply traction load
To supply industrial load at constant voltage
Voltage at the toad end of the feeder
For none of the above purpose

Q.29

Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?

Series generator
Shunt generator
Compound generator
None of the above

Q.30

The material for commutator brushes is generally

Mica
Copper
Cast iron
Carbon

0 h : 0 m : 1 s