_ The essential condition for parallel operation of two D.C. generators is that they have$?

the same drooping voltage characteristics

_The function of pole shoes in the case of D.C. machine is$?

To reduce the reluctance of the magnetic path

To spread out the flux to achieve uniform flux density

To discharge all the above functions

_Armature reaction in a generator results in$?

Demagnetization of trailing pole tip and magnetization of leading pole tip

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

_The main factor which leads to unstable parallel operation of flat and over compounded generators is$?

unequal number of turns in their series field windings

their rising voltage characteristics

unequal number of turns in their series field windings

unequal speed regulation of their primemovers

unequal series field resistances

_In D.C. generators the polarity of the interpoles$?

Is the same as that of the immediately preceding pole

Is the same as that of the main pole ahead

Is the same as that of the immediately preceding pole

Is opposite to that of the main pole ahead

Is neutral as these poles do not play part in generating e.m.f.

_In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when$?

The generator runs on full load

There is no load on the generator

The generator runs on full load

The generator runs on designed speed

_Lap winding is composed of$?

That even number which is exact multiple of poles + 2

That even number which is exact multiple of poles

_The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage$?

May be greater or less than 250 V

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

Cross magnetization as well as magnetization

Cross-magnetization as well as demagnetizing

Eddy currents are induced in the pole shoes of a D.C. machine due to$?

Relative rotation between field and armature

Flashing the field of D.C. generator means$?

Making the magnetic losses of forces parallel

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

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

All the four poles are south poles

All the four poles are north poles

Alternate poles are north and south

All the four poles are south poles

Two north poles follow two south poles

Two generators are running in parallel. One of the generators may run as motor for which of the following reasons??

The direction of that generator is reversed

The speed of that generator is increased

The field of that generator is weakened

That generator takes large share of loads

In the case of lap winding resultant pitch is?

Multiplication of front and back pitches

Division of front pitch by back pitch

Difference of front and back pitches

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

clearance between tips of the adjacent pole shoes

Open circuited armature coil of a D.C. machine is?

Identified by the scarring of the commutator segment to which open circuited coil is connected

Indicated by a spark completely around the commutator

To avoid formation of grooves in the commutator of a D.C. machine?

The brushes of same polarity should track each other

The brushes of opposite polarity should track each other

The brushes of same polarity should track each other

Brush position has no effect on the commutator grooving

When two D.C. generators are running in parallel an equalizer bar is used?

To increase the generated e.m.f.

To reduce the combined effect of armature reaction of both the machines

So that the two identical machines will pass approximately equal currents to the load

In a four-pole D.C. machine?

All the four poles are south poles

All the four poles are north poles

Alternate poles are north and south

All the four poles are south poles

Two north poles follow two south poles

A cumulatively compounded long shunt generator when operating as a motor would be

Cumulatively compounded short shunt

Cumulatively compounded long shunt

Differentially compounded long shunt

Cumulatively compounded short shunt

Differentially compounded short shunt

In a D.C. machine, short-circuited field coil will result in

unbalanced magnetic pull producing vibrations

reduction of generated voltage for which excitation has to be increased to maintain the voltage

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

In case of a flat compounded generator

Speed varies in proportion to the load on the 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

378 + Mcqs in D.C. Generators in Electrical Engineering Page 7 McqOptions

301.	_ Two generators A and B have 6 poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be$?
A.	2 : 3
B.	3 : 1
C.	3 : 2
D.	1 : 3
Answer» C. 3 : 2

Discussion

302.	_ In D.C. generators, lap winding is used for$?
A.	High voltage, high current
B.	Low voltage, high current
C.	High voltage, low current
D.	Low voltage, low current
Answer» C. High voltage, low current

Discussion

303.	_ The essential condition for parallel operation of two D.C. generators is that they have$?
A.	same kW rating
B.	the same operation r.p.m.
C.	the same drooping voltage characteristics
D.	same percentage regulation
Answer» D. same percentage regulation

Discussion

304.	_The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be$?
A.	640 V
B.	620 V
C.	600 V
D.	580 V
Answer» E.

Discussion

305.	_In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilized is called$?
A.	Rotor
B.	Stator
C.	Field
D.	Armature
Answer» E.

Discussion

306.	_The series field of a short-shunt D.C. generator is excited by$?
A.	external current
B.	armature current
C.	shunt current
D.	load current
Answer» E.

Discussion

307.	_The function of pole shoes in the case of D.C. machine is$?
A.	To reduce the reluctance of the magnetic 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» E.

Discussion

308.	_Armature reaction in a generator results in$?
A.	Demagnetization of leading pole tip and magnetization of trailing pole tip
B.	Demagnetization of trailing pole tip and magnetization of leading pole tip
C.	Demagnetizing the center of all poles
D.	Magnetizing the center of all poles
Answer» B. Demagnetization of trailing pole tip and magnetization of leading pole tip

Discussion

309.	_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» E.

Discussion

310.	_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» C. Half the number of poles

Discussion

311.	_The main factor which leads to unstable parallel operation of flat and over compounded generators is$?
A.	their rising voltage characteristics
B.	unequal number of turns in their series field windings
C.	unequal speed regulation of their primemovers
D.	unequal series field resistances
Answer» B. unequal number of turns in their series field windings

Discussion

312.	_The armature core of a D.C. generator is usually made of$?
A.	Silicon steel
B.	Copper
C.	Nonferrous material
D.	Cast-iron
Answer» B. Copper

Discussion

313.	_A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave$?
A.	will be zero
B.	will be of 5 Hz
C.	will be of 5 xiVHz
D.	will be of v Hz 5
Answer» C. will be of 5 xiVHz

Discussion

314.	_In D.C. generators the polarity of the interpoles$?
A.	Is the same as that of the main pole ahead
B.	Is the same as that of the immediately preceding pole
C.	Is opposite to that of the main pole ahead
D.	Is neutral as these poles do not play part in generating e.m.f.
Answer» B. Is the same as that of the immediately preceding pole

Discussion

315.	_The voltage drop for which of the following types of brush can be expected to be least?$?
A.	Graphite brushes
B.	Carbon brushes
C.	Metal graphite brushes
D.	None of the above
Answer» D. None of the above

Discussion

316.	_In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when$?
A.	There is no load on the generator
B.	The generator runs on full load
C.	The generator runs on overload
D.	The generator runs on designed speed
Answer» B. The generator runs on full load

Discussion

317.	_Lap winding is composed of$?
A.	Any even number of conductors
B.	Any odd number of conductors
C.	That even number which is exact multiple of poles + 2
D.	That even number which is exact multiple of poles
Answer» B. Any odd number of conductors

Discussion

318.	_The insulating material used between the commutator segments is normally$?
A.	Graphite
B.	Paper
C.	Mica
D.	Insulating varnish
Answer» D. Insulating varnish

Discussion

319.	_The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage$?
A.	Will be less than 250 V
B.	Will always be 250 V
C.	May be greater or less than 250 V
D.	None of the above
Answer» D. None of the above

Discussion

320.	_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» D. Cross magnetization only

Discussion

321.	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» D. All above

Discussion

322.	Flashing the field of D.C. generator means$?
A.	Neutralizing 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» C. Making the magnetic losses of forces parallel

Discussion

323.	The e.m.f. generated in a D.C. generator is directly proportional to$?
A.	Flux/pole
B.	Speed of armature
C.	Number of poles
D.	All of the above
Answer» C. Number of poles

Discussion

324.	The material for commutator brushes is generally$?
A.	Mica
B.	Copper
C.	Cast iron
D.	Carbon
Answer» E.

Discussion

325.	Armature reaction of an unsaturated D.C. machine is$?
A.	Cross-magnetizing
B.	Demagnetizing
C.	Magnetizing
D.	None of above
Answer» B. Demagnetizing

Discussion

326.	Which generator would you prefer for feeding long D.C. transmission lines?$?
A.	Series generator
B.	Shunt generator
C.	Over compound generator
D.	Flat compound generator
Answer» D. Flat compound generator

Discussion

327.	Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.$?
A.	Series field
B.	Compensating field
C.	Inter pole field
D.	Shunt field
Answer» E.

Discussion

328.	An exciter for a turbo generator is a$?
A.	Separately excited generator
B.	Shunt generator
C.	Series generator
D.	Compound generator
Answer» C. Series generator

Discussion

329.	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 poles
Answer» C. All the four poles are south poles

Discussion

330.	The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be$?
A.	150 V
B.	Less than 150 V
C.	Greater than 150 V
D.	None of the above
Answer» D. None of the above

Discussion

331.	The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be?
A.	150 V
B.	Less than 150 V
C.	Greater than 150 V
D.	None of the above
Answer» D. None of the above

Discussion

332.	In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called?
A.	rotor
B.	stator
C.	field
D.	armature
Answer» E.

Discussion

333.	In a shunt generator the voltage build up is generally restricted by?
A.	speed limitation
B.	armature heating
C.	insulation restrictions
D.	saturation of iron
Answer» E.

Discussion

334.	Two generators are running in parallel. One of the generators may run as motor for which of the following reasons??
A.	The direction of that generator is reversed
B.	The speed of that generator is increased
C.	The field of that generator is weakened
D.	That generator takes large share of loads
Answer» E.

Discussion

335.	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» E.

Discussion

336.	In a D.C. generator the actual flux distribution depends upon?
A.	size of air gap
B.	shape of the pole shoe
C.	clearance between tips of the adjacent pole shoes
D.	all of the above
Answer» E.

Discussion

337.	Open circuited armature coil of a D.C. machine is?
A.	Identified by the scarring of the commutator segment to which open circuited coil is connected
B.	Indicated by a spark completely around the commutator
C.	Both (A) and (B)
D.	None of the above
Answer» D. None of the above

Discussion

338.	To avoid formation of grooves in the commutator of a D.C. machine?
A.	The brushes of opposite polarity should track each other
B.	The brushes of same polarity should track each other
C.	Brush position has no effect on the commutator grooving
D.	All of the above
Answer» B. The brushes of same polarity should track each other

Discussion

339.	When two D.C. generators are running in parallel an equalizer bar is used?
A.	To increase the series flux
B.	To increase the generated e.m.f.
C.	To reduce the combined effect of armature reaction of both the machines
D.	So that the two identical machines will pass approximately equal currents to the load
Answer» E.

Discussion

340.	In D.C. generators on no-load, the air gap flux distribution in space is?
A.	Sinusoidal
B.	Triangular
C.	Pulsating
D.	Flat topped
Answer» E.

Discussion

341.	An exciter for a turbo generator is a?
A.	Separately excited generator
B.	Shunt generator
C.	Series generator
D.	Compound generator
Answer» C. Series generator

Discussion

342.	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 poles
Answer» C. All the four poles are south poles

Discussion

343.	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» D. Are farthest from the poles

Discussion

344.	Brushes of D.C. machines are made of?
A.	Carbon
B.	Soft copper
C.	Hard copper
D.	All of above
Answer» B. Soft copper

Discussion

345.	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» B. Number of armature coil sides

Discussion

346.	In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralized by all of the following except?
A.	Interpoles
B.	Dummy coils
C.	Compensating winding
D.	Shifting of axis of brushes
Answer» C. Compensating winding

Discussion

347.	A cumulatively compounded long shunt generator when operating as a motor would be
A.	Cumulatively compounded long shunt
B.	Differentially compounded long shunt
C.	Cumulatively compounded short shunt
D.	Differentially compounded short shunt
Answer» C. Cumulatively compounded short shunt

Discussion

348.	In a D.C. machine, short-circuited field coil will result in
A.	odour of barning insulation
B.	unbalanced magnetic pull producing vibrations
C.	reduction of generated voltage for which excitation has to be increased to maintain the voltage
D.	all above
Answer» E.

Discussion

349.	Compensating windings are used in D.C. generators
A.	Mainly to reduce the eddy currents by providing local short-circuits
B.	To provide path for the circulation of cooling air
C.	To neutralize the cross-magnetizing effect of the armature reaction
D.	None of the above
Answer» D. None of the above

Discussion

350.	In case of a flat compounded generator
A.	Voltage generated is less than the rated voltage
B.	Generated voltage is proportional to the load on the generator
C.	Voltage remains constant irrespective of the load
D.	Speed varies in proportion to the load on the generator
Answer» D. Speed varies in proportion to the load on the generator

Discussion

Explore topic-wise MCQs in Electrical Engineering.

_ Two generators A and B have 6 poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be$?

_ In D.C. generators, lap winding is used for$?

_ The essential condition for parallel operation of two D.C. generators is that they have$?

_The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be$?

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

_The series field of a short-shunt D.C. generator is excited by$?

_The function of pole shoes in the case of D.C. machine is$?

_Armature reaction in a generator results in$?

_In D.C. generators, the cause of rapid brush wear may be$?

_In lap winding, the number of brushes is always$?

_The main factor which leads to unstable parallel operation of flat and over compounded generators is$?

_The armature core of a D.C. generator is usually made of$?

_A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave$?

_In D.C. generators the polarity of the interpoles$?

_The voltage drop for which of the following types of brush can be expected to be least?$?

_In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when$?

_Lap winding is composed of$?

_The insulating material used between the commutator segments is normally$?

_The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage$?

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

Eddy currents are induced in the pole shoes of a D.C. machine due to$?

Flashing the field of D.C. generator means$?

The e.m.f. generated in a D.C. generator is directly proportional to$?

The material for commutator brushes is generally$?

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

Which generator would you prefer for feeding long D.C. transmission lines?$?

Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.$?

An exciter for a turbo generator is a$?

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

The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be$?

The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be?

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

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

Two generators are running in parallel. One of the generators may run as motor for which of the following reasons??

In the case of lap winding resultant pitch is?

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

Open circuited armature coil of a D.C. machine is?

To avoid formation of grooves in the commutator of a D.C. machine?

When two D.C. generators are running in parallel an equalizer bar is used?

In D.C. generators on no-load, the air gap flux distribution in space is?

An exciter for a turbo generator is a?

In a four-pole D.C. machine?

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

Brushes of D.C. machines are made of?

In case of D.C. machine winding, number of commutator segments is equal to?

In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralized by all of the following except?

A cumulatively compounded long shunt generator when operating as a motor would be

In a D.C. machine, short-circuited field coil will result in

Compensating windings are used in D.C. generators

In case of a flat compounded generator