D.c. Generators MCQs

Option A: only if the load current is zero

Option B: only if the load current is not zero

Option C: irrespective of the value of load current

Option D: none of the above

Correct Answer: only if the load current is not zero ✔

Option A: Lenz’s law

Option B: Ohm’s law

Option C: Faraday’s law of electromagnetic induction

Option D: none of the above

Correct Answer: Faraday’s law of electromagnetic induction ✔

Option A: will be less than 250 V

Option B: will always be 250 V

Option C: may be greater or less than 250 V

Option D: none of the above

Correct Answer: may be greater or less than 250 V ✔

Option A: 150 V

Option B: less than 150 V

Option C: greater than 150 V

Option D: none of the above

Correct Answer: 150 V ✔

Option A: only if the resistance of the field circuit is less than critical value

Option B: only if the resistance of the field circuit is greater than critical value

Option C: irrespective of the value of the resistance in the field circuit

Option D: none

Correct Answer: only if the resistance of the field circuit is less than critical value ✔

Option A: 100% regulation

Option B: infinite regulation

Option C: 50% regulation

Option D: 1% regulation

Correct Answer: 1% regulation ✔

Option A: 270 V

Option B: 267.5 V

Option C: 265 V

Option D: 257.4 V

Correct Answer: 267.5 V ✔

Option A: same kW rating

Option B: the same operation r.p.m.

Option C: the same drooping voltage characteristics

Option D: same percentage regulation

Correct Answer: the same drooping voltage characteristics ✔

Option A: to increase the series flux

Option B: to increase the generated e.m.f.

Option C: to reduce the combined effect of ar-mature reaction of both the machines

Option D: so that the two identical machines will pass approximately equal cur¬rents to the load

Correct Answer: so that the two identical machines will pass approximately equal cur¬rents to the load ✔

Option A: The direction of that generator is reversed

Option B: The speed of that generator is increased

Option C: The field of that generator is weakened

Option D: That generator takes large share of loads

Correct Answer: That generator takes large share of loads ✔

Option A: Shunt generators

Option B: Series generators

Option C: Compound generators

Option D: None of the above

Correct Answer: Shunt generators ✔

Option A: Self-excited generator

Option B: Separately excited generator

Option C: Level compounded generator

Option D: All of the above

Correct Answer: Level compounded generator ✔

Option A: reverse the field connections

Option B: increase the field resistance

Option C: increase the speed of primemover

Option D: check armature insulation resistance

Correct Answer: reverse the field connections ✔

Option A: their rising voltage characteristics

Option B: unequal number of turns in their series field windings

Option C: unequal speed regulation of their primemovers

Option D: unequal series field resistances

Correct Answer: their rising voltage characteristics ✔

Option A: to increase the speed and hence generated e.m.f.

Option B: to increase the series flux

Option C: so that two similar machines will pass approximately equal currents to the load

Option D: to reduce the combined effect of ar-mature reaction of both machines

Correct Answer: so that two similar machines will pass approximately equal currents to the load ✔

Option A: rising voltage characteristics

Option B: identical voltage characteristics

Option C: drooping voltage characteristics

Option D: linear voltage characteristics

Correct Answer: drooping voltage characteristics ✔

Option A: 40 percent

Option B: 25 percent

Option C: 10 percent

Option D: 5 percent

Correct Answer: 5 percent ✔

Option A: field

Option B: brushes

Option C: armature

Option D: load

Correct Answer: field ✔

Option A: external current

Option B: armature current

Option C: shunt current

Option D: load current

Correct Answer: load current ✔

Option A: is always present

Option B: is always absent

Option C: may be sometimes present

Option D: none of the above

Correct Answer: is always present ✔

Option A: slots

Option B: armature conductors

Option C: winding elements

Option D: poles

Correct Answer: winding elements ✔

Option A: any even number of conductors

Option B: any odd number of conductors

Option C: that even number which is exact multiple of poles + 2

Option D: that even number which is exact multiple of poles

Correct Answer: that even number which is exact multiple of poles + 2 ✔

Option A: 2

Option B: 4

Option C: 6

Option D: 8

Correct Answer: 4 ✔

Option A: external resistance = internal char-acteristic – armature reaction

Option B: internal characteristic = magnetisation characteristic – ohmic drop

Option C: external characteristic = magnetisation characteristic – ohmic drop – armature reaction

Option D: magnetisation characteristic = external characteristic

Correct Answer: external characteristic = magnetisation characteristic – ohmic drop – armature reaction ✔

Option A: increasing its field resistance

Option B: decreasing its field resistance

Option C: increasing its speed

Option D: decreasing its speed

Correct Answer: increasing its speed ✔

Option A: Series generator

Option B: Shunt generator

Option C: Over compound generator

Option D: Flat compound generator

Correct Answer: Over compound generator ✔

Option A: Series field

Option B: Compensating field

Option C: Inter pole field

Option D: Shunt field

Correct Answer: Shunt field ✔

Option A: demagnetisation of leading pole tip and magnetisation of trailing pole tip

Option B: demagnetisation of trailing pole tip and magnetisation of leading pole tip

Option C: damagnetising the center of all poles

Option D: magnetising the center of all poles

Correct Answer: demagnetisation of leading pole tip and magnetisation of trailing pole tip ✔

Option A: zero

Option B: small

Option C: the same as rated voltage

Option D: high

Correct Answer: zero ✔

Option A: to reduce eddy current losses

Option B: to enhance flux density

Option C: to amplify voltage

Option D: to provide mechanical balance for the rotor

Correct Answer: to provide mechanical balance for the rotor ✔

Option A: zero

Option B: about 2 V

Option C: about 50 V

Option D: 220 V

Correct Answer: about 2 V ✔

Option A: 150 V

Option B: 175 V

Option C: 240 V

Option D: 290 V

Correct Answer: 240 V ✔

Option A: will be zero

Option B: will be of 5 Hz

Option C: will be of 5 xiVHz

Option D: will be of v Hz 5

Correct Answer: will be of 5 Hz ✔

Option A: to reduce eddy current losses

Option B: to enhance flux density

Option C: to amplify voltage

Option D: to provide mechanical balance for the rotor

Correct Answer: to provide mechanical balance for the rotor ✔

Option A: sinusoidal

Option B: triangular

Option C: pulsating

Option D: flat topped

Correct Answer: flat topped ✔

Option A: armature reaction

Option B: armature resistance drop

Option C: field weakening due to armature reaction and armature

Option D: commutation

Correct Answer: commutation ✔

Option A: interpoles

Option B: dummy coils

Option C: compensating winding

Option D: shifting of axis of brushes

Correct Answer: dummy coils ✔

Option A: there is no load on|he generator

Option B: the generator runs on full load

Option C: the generator runs on overload

Option D: the generator runs on designed speed

Correct Answer: there is no load on|he generator ✔

Option A: negligibly low

Option B: equal to no-load terminal voltage

Option C: more than no-load terminal voltage

Option D: less than no-load terminal voltage

Correct Answer: equal to no-load terminal voltage ✔

Option A: flux/pole

Option B: speed of armature

Option C: number of poles

Option D: all of the above

Correct Answer: speed of armature ✔

Option A: is the same as that of the main pole ahead

Option B: is the same as that of the immediately preceding pole

Option C: is opposite to that of the main pole ahead

Option D: is neutral as these poles do not play part in generating e.m.f.

Correct Answer: is the same as that of the main pole ahead ✔

Option A: almost zero

Option B: less than no load terminal voltage

Option C: more than no load terminal voltage

Option D: equal to no-load terminal voltage

Correct Answer: more than no load terminal voltage ✔

Option A: flux density

Option B: reluctance

Option C: ampere-turns

Option D: resistance

Correct Answer: reluctance ✔

Option A: Series generator

Option B: Shunt generator

Option C: Compound generator

Option D: None of the above

Correct Answer: None of the above ✔

Option A: Series generator

Option B: Shunt generator

Option C: Compound generator

Option D: Separately excited generator

Correct Answer: Series generator ✔

Option A: r.p.m. is more than 300

Option B: r.p.m. is less than 300

Option C: number of poles is 4

Option D: number of poles is 2

Correct Answer: number of poles is 2 ✔

Option A: series generator

Option B: shunt generator

Option C: long shunt compound generator

Option D: any of’the above

Correct Answer: long shunt compound generator ✔

Option A: voltage generated is less than the rated voltage

Option B: generated voltage is proportional to the load on the generator

Option C: voltage remains constant irrespective of the load

Option D: speed varies in proportion to the load on the generator

Correct Answer: voltage remains constant irrespective of the load ✔

Option A: neutralise the commutating self induced e.m.f.

Option B: neutralise the armature reaction flux

Option C: neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil

Option D: perform none of the above functions

Correct Answer: neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil ✔

Option A: series generator

Option B: shunt generator

Option C: compound generator

Option D: self-excited generator

Correct Answer: self-excited generator ✔

Option A: separately excited generator

Option B: shunt generator

Option C: series generator

Option D: compound generator

Correct Answer: shunt generator ✔

Option A: to supply traction load

Option B: to supply industrial load at constant voltage

Option C: voltage at the toad end of the feeder

Option D: for none of the above purpose

Correct Answer: voltage at the toad end of the feeder ✔

Option A: increase

Option B: decrease

Option C: remain unaffected

Option D: fluctuate heavily

Correct Answer: decrease ✔

Option A: voltage of the incoming generator should be same as that of bus bar

Option B: polarity of incoming generator should be same as that of bus bar

Option C: all the series fields should be run in parallel by means of equilizer connection

Option D: series fields of all generators should be either on positive side or negative side of the armature

Correct Answer: series fields of all generators should be either on positive side or negative side of the armature ✔

Option A: identified by the scarring of the commutator segment to which open circuited coil is connected

Option B: indicated by a spark completely around the commutator

Option C: both A. and (b)

Option D: none of the above

Correct Answer: C. both A. and (b) ✔

Option A: any even number of conductors

Option B: any odd number of conductors

Option C: that even number which is exact multiple of poles + 2

Option D: that even number which is exact multiple of poles

Correct Answer: any even number of conductors ✔

Option A: brushes should be of proper grade and size

Option B: brushes should smoothly run in the holders

Option C: smooth, concentric commutator properly undercut

Option D: all of the above

Correct Answer: all of the above ✔

Option A: total copper loss and mechanical loss

Option B: armature copper loss and iron loss

Option C: shunt field copper loss and mechanical loss

Option D: iron loss and mechanical loss

Correct Answer: iron loss and mechanical loss ✔

Option A: silicon steel

Option B: copper

Option C: non-ferrous material

Option D: cast-iron

Correct Answer: silicon steel ✔

Option A: rotor

Option B: stator

Option C: field

Option D: armature

Correct Answer: armature ✔

Option A: E/2

Option B: 2E

Option C: slightly less than E

Option D: E

Correct Answer: 2E ✔

Option A: rectifier

Option B: primemover

Option C: rotating amplifier

Option D: power pump

Correct Answer: rotating amplifier ✔

Option A: Graphite brushes

Option B: Carbon brushes

Option C: Metal graphite brushes

Option D: None of the above

Correct Answer: Metal graphite brushes ✔

Option A: 2 : 3

Option B: 3 : 1

Option C: 3 : 2

Option D: 1 : 3

Correct Answer: 3 : 1 ✔

Option A: number of pole pairs

Option B: number of poles

Option C: number of parallel paths

Option D: number of commutator segments

Correct Answer: number of pole pairs ✔

Option A: high voltage, high current

Option B: low voltage, high current

Option C: high voltage, low current

Option D: low voltage, low current

Correct Answer: low voltage, high current ✔

Option A: using conductor of annealed copper

Option B: using commutator with large number of segments

Option C: using carbon brushes of superior quality

Option D: using equiliser rings

Correct Answer: using carbon brushes of superior quality ✔

Option A: abrasion from dust

Option B: excessive spring pressure

Option C: rough commutator bars

Option D: high mica insulation between com-mutation bars

Correct Answer: all of the above factors ✔

Option A: Dummy coils

Option B: Commutator

Option C: Eye bolt

Option D: Equilizer rings

Correct Answer: Commutator ✔

Option A: mainly to reduce the eddy currents by providing local short-circuits

Option B: to provide path for the circulation of cooling air

Option C: to neutralise the cross-magnetising effect of the armature reaction

Option D: none of the above

Correct Answer: to neutralise the cross-magnetising effect of the armature reaction ✔

Option A: Insulation failure between two commutator bars

Option B: Insulation failure between two turns of a coil

Option C: Two of more turns of the same coil getting grounded

Option D: All of the above

Correct Answer: All of the above ✔

Option A: speed of armature

Option B: type of winding

Option C: voltage

Option D: amount of current to be collected

Correct Answer: amount of current to be collected ✔

Option A: electromagnets

Option B: permanent magnets

Option C: both A. and B.

Option D: none of the above

Correct Answer: electromagnets ✔

Option A: the brushes of opposite polarity should track each other

Option B: the brushes of same polarity should track each other

Option C: brush position has no effect on the commutator grooving

Option D: None

Correct Answer: the brushes of opposite polarity should track each other ✔

Option A: reduces generator e.m.f.

Option B: increases armature speed

Option C: reduces interpoles flux density

Option D: results in sparking trouble

Correct Answer: reduces generator e.m.f. ✔

Option A: cumulatively compounded long shunt

Option B: deferentially compounded long shunt

Option C: cumulatively compounded short shunt

Option D: differentially compounded short shunt

Correct Answer: deferentially compounded long shunt ✔

Option A: along neutral axis

Option B: along field axis

Option C: in any of the above positions

Option D: in none of the above positions

Correct Answer: along neutral axis ✔

Option A: Compensating winding in a D.C. machine helps in commutation

Option B: In a D. C. generator interpoles winding is connected in series with the armature winding

Option C: Back pitch and front pitch are both odd and approximately equal to the pole pitch

Option D: Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators

Correct Answer: D. Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators ✔

Option A: just ahead of magnetic neutral axis

Option B: in magnetic neutral axis

Option C: just behind the magnetic neutral axis

Option D: none

Correct Answer: just ahead of magnetic neutral axis ✔

Option A: lap winding

Option B: wave moving

Option C: duplex winding

Option D: any of the above

Correct Answer: lap winding ✔

Option A: brushes

Option B: field

Option C: armature

Option D: load

Correct Answer: field ✔

Option A: 640 V

Option B: 620 V

Option C: 600 V

Option D: 580 V

Correct Answer: 580 V ✔

Option A: multiplication of front and back pitches

Option B: division of front pitch by back pitch

Option C: sum of front and back pitches

Option D: difference of front and back pitches

Correct Answer: difference of front and back pitches ✔

Option A: to reduce the reluctance of the mag¬netic path

Option B: to spread out the flux to achieve uniform flux density

Option C: to support the field coil

Option D: to discharge all the above functions

Correct Answer: to discharge all the above functions ✔

Option A: neutralising residual magnetism

Option B: creating residual magnetism by a D.C. source

Option C: making the magnetic losses of forces parallel

Option D: increasing flux density by adding extra turns of windings on poles

Correct Answer: B. creating residual magnetism by a D.C. source ✔

Option A: rotary converter

Option B: mercury are rectifier

Option C: induction motor D.C. generator set

Option D: synchronous motor D.C. generator set

Correct Answer: C. induction motor D.C. generator set ✔

Option A: number of armature coils

Option B: number of armature coil sides

Option C: number of armature conductors

Option D: number of armature turns

Correct Answer: number of armature coils ✔

Option A: lap winding

Option B: wave winding

Option C: delta winding

Option D: duplex wave winding

Correct Answer: lap winding ✔

Option A: wave wound

Option B: lap wound

Option C: delta wound

Option D: duplex wound

Correct Answer: lap wound ✔

Option A: oscillating magnetic field

Option B: pulsating magnetic flux

Option C: relative rotation between field and armature

Option D: all above

Correct Answer: relative rotation between field and armature ✔

Option A: to avoid sudden loading of the primemover

Option B: to avoid mechanicaljerk to the shaft

Option C: to avoid burning of switch contacts

Option D: all above

Correct Answer: all above ✔

Option A: crossmagnetising

Option B: demagnetising

Option C: magnetising

Option D: none of above

Correct Answer: crossmagnetising ✔

Option A: demagnetisation only

Option B: cross magnetisation as well as mag¬netisation

Option C: crossmagnetisation as well as demagnetising

Option D: cross magnetisation only

Correct Answer: crossmagnetisation as well as demagnetising ✔

Option A: lie under south pole

Option B: lie under north pole

Option C: lie under interpolar region

Option D: are farthest from the poles

Correct Answer: lie under interpolar region ✔

Option A: graphite

Option B: paper

Option C: mica

Option D: insulating varnish

Correct Answer: mica ✔

Option A: mica

Option B: copper

Option C: cast iron

Option D: carbon

Correct Answer: carbon ✔

Option A: 4

Option B: 8

Option C: 16

Option D: 32

Correct Answer: 8 ✔

Option A: Blv

Option B: Blv2

Option C: Bl2v

Option D: Bl2v2

Correct Answer: Blv ✔

Option A: imperfect brush contact

Option B: field resistance less than the critical resistance

Option C: no residual magnetism in the generator

Option D: faulty shunt connections tending to reduce the residual magnetism

Correct Answer: field resistance less than the critical resistance ✔

Option A: carbon

Option B: soft copper

Option C: hard copper

Option D: all of above

Correct Answer: carbon ✔