Question is ⇒ The critical resistance of the D.C. generator is the resistance of, Options are ⇒ (A) field, (B) brushes, (C) armature, (D) load, (E) , Leave your comments or Download question paper.

Question is ⇒ The critical resistance of the D.C. generator is the resistance of, Options are ⇒ (A) field, (B) brushes, (C) armature, (D) load, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	The critical resistance of the D.C. generator is the resistance of
A.	field [Correct Answer]
B.	brushes [Wrong Answer]
C.	armature [Wrong Answer]
D.	load [Wrong Answer]
View Answer 13 -7 Explanation:- Answer : A Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ If the no load voltage of a certain generator is 210 V and the rated voltage is 200 V, then the voltage regulation is
0.025
0.05
0.1
0.15

⇒ An external resistance added in the field of a D.C. shunt generator will
decrease the voltage of the generator
increase the voltage of the generator
increase the power delivered
increase the speed of the generator

⇒ The essential condition for parallel operation of two D.C. generators is that they have
same kW rating
the same operation r.p.m.
the same drooping voltage characteristics
same percentage regulation

⇒ Lap winding is composed of
any even number of conductors
any odd number of conductors
that even number which is exact multiple of poles + 2
that even number which is exact multiple of poles

⇒ To achieve sparkless commutation brushes of a D.C. generator are rocked ahead so as to bring them
just ahead of magnetic neutral axis
in magnetic neutral axis
just behind the magnetic neutral axis

⇒ 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

⇒ The armature core of a D.C. generator is usually made of
silicon steel
copper
non-ferrous material
cast-iron

⇒ In case of D.C. machine winding, number of commutator segments is equal to
number of armature coils
number of armature coil sides
number of armature conductors
number of armature turns

⇒ In a lap wound D.C. generator having p as number of poles and Z as number of conductors, the maximum number of equilizer rings will be
Z
P

⇒ 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 support the field coil
to discharge all the above functions

⇒ If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to
reverse the field connections
increase the field resistance
increase the speed of primemover
check armature insulation resistance

⇒ Iron losses in a D.C. machine are independent of variations in
speed
load
voltage
speed and voltage

⇒ Shunt generators are most suited for stable parallel operation because of their
rising voltage characteristics
identical voltage characteristics
drooping voltage characteristics
linear Voltage characteristics

⇒ In D.C. generators, lap winding is used for
high voltage, high current
low voltage, high current
high voltage, low current
low voltage, low current

⇒ 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

⇒ In a level compounded D.C. generator, full load terminal voltag-e is
negligibly low
equal to no-load terminal voltage
more than no-load terminal voltage
less than no-load terminal voltage

⇒ In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except
interpoles
dummy coils
compensating winding
shifting of axis of brushes

⇒ Which generator cannot start if there is no residual magnetism ?
Series generator
Shunt generator
Separately excited generator
All of the above

⇒ 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

⇒ D.C. generator generates
a.c. voltage in the armature
d.c. voltage in the armature
a.c. superimposed over d.c.
none of the above

⇒ D.C. generators are connected to the busbars or disconnected from them only under the floating condition
to avoid sudden loading of the primemover
to avoid mechanical jerk to the shaft
to avoid burning of switch contacts
all above

⇒ In D.C. generators the polarity of the interpoles
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.

⇒ When two D.C. generators are running in parallel an equilizer bar is used
to increase the series flux
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

⇒ Magnetic field in a D.C. generator is produced by
electromagnets
permanent magnets
both (a) and (b)
none of the above

⇒ In a D.C. machine, fractional pitch winding is used
to increase the generated voltage
to reduce sparking
to save the copper because of shorter end connections
due to (b) and (c) above

⇒ In D.C. generators, the brushes remain in contact with conductors which
lie under south pole
lie under north pole
lie in the inter-polar gaps
none of the above

⇒ In a D.C. generator the critical resistance can be increased by
increasing its field resistance
decreasing its field resistance
increasing its speed
decreasing its speed

⇒ In a shunt generator the voltage build up is generally restricted by
speed limitation
armature heating
insulation restrictions
saturation of iron

⇒ 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

⇒ A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be
zero
about 2 V
about 50V
220 V