Question is ⇒ In which of the following applications D.C. series motor is invariably tried?, Options are ⇒ (A) Starter for a car, (B) Drive for a water pump, (C) Fan motor, (D) Motor operation in A.C. or D.C., (E) , Leave your comments or Download question paper.

Question is ⇒ In which of the following applications D.C. series motor is invariably tried?, Options are ⇒ (A) Starter for a car, (B) Drive for a water pump, (C) Fan motor, (D) Motor operation in A.C. or D.C., (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	In which of the following applications D.C. series motor is invariably tried?
A.	Starter for a car [Correct Answer]
B.	Drive for a water pump [Wrong Answer]
C.	Fan motor [Wrong Answer]
D.	Motor operation in A.C. or D.C. [Wrong Answer]
View Answer 7 -4 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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⇒ In D.C. shunt motors as load is reduced
the speed will increase abruptly
the speed will increase in proportion to reduction in load
the speed will remain almost constant
the speed will reduce

⇒ In a D.C. motor, unidirectional torque is produced with the help of
end plates
bushes
commutator
both (b) and (c)

⇒ For starting a D.C. motor a starter is required because
it limits the speed of the motor
it limits the starting current to a safe value
it starts the motor
none of the above

⇒ Between Field's test and Hopkinson's test the main common thing is that both
use negligible power
are regenerative tests
need two similar mechanicallycoupled motors
need two electrically coupled series motors

⇒ The variable resistor shunting the field of a D.C. series motor is called a
armature divertor
voltage regulator
field divertor
potential divider

⇒ The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is
0.0236
0.0476
0.0677
0.0884

⇒ The ratio of starting torque to fullload torque is least in case of
series motors
shunt motors
compound motors
none of the above

⇒ Which of the following methods of braking is used in rolling mills ?
Dynamic braking
Plugging
Regenerative braking
Mechanical brakes

⇒ Which of the following method of speed control, of D.C. machine will offer minimum efficiency ?
Voltage control method
Field control method
Armature control method
All above methods

⇒ Which of the following methods is most effective in finding out the no load losses in a large D.C. shunt motor ?
Field's test
Ward-Leonard test
Block rotor test
Swinburne's test

⇒ If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
nothing will happen to the motor
this will make armature to take heavy current, possibly burning it
this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
motor will run at very slow speed

⇒ D.C. generators are normally designed for maximum efficiency around
full-load
rated r.p.m.
rated voltage
all of the above

⇒ Which of the following losses are significantly reduced by laminating the core of a D.C. generator ?
Hysteresis losses
Eddy current losses
Copper losses
Windage losses

⇒ Which of the following motors is usually used in house-hold refrigerators ?
D.C. shunt motor
D.C. series motor
Single phase induction motor (split phase start or induction run motor)
Reluctance motor

⇒ Which of the following motors is most suitable for signalling devices and many kinds of timers ?
D.C. shunt motor
D.C. series motor
Induction motor
Reluctance motor

⇒ In D.C. motor which of the following can sustain the maximum temperature rise?
Slip rings
Commutator
Field winding
Armature winding

⇒ Which of the following methods gives the greatest breaking torque ?
Regenerative braking
Plugging
Rheostatic braking
None of the above.

⇒ In case of conductively compensated D.C. series motors, the compensating winding is provided
as separately wound unit
in parallel with armature winding
in series with armature winding
in parallel with field winding

⇒ A wide and very sensitive speed control is usually required in case of
elevators
steel rolling mills
colliery winders
all of the above

⇒ In the D.C. motor the iron losses occur in
the field
the armature
the brushes
the commutator

⇒ In Ward Leonard method of speed control of a D.C. motor, change in speed of motor is obtained by the
change in armature voltage of D.C. motor
change in the field excitation of the D.C. motor
change in armature current of D.C. motor
change in supply voltage

⇒ Sparking at the commutator of a D.C. motor may result in
damage to commutator segments
damage to commutator insulation
increased power consumption
all of the above

⇒ The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is
4.0
2.0
1.0
0.5

⇒ If t be the thickness of the laminations, then eddy current loss in a generator. will vary as
¹/_t
¹/_t²
t
t²

⇒ The speed regulation of a D.C. motor is

lowest speed

highest speed

highest speed - lowest speed

average speed

no-load speed - full-load speed

full-load speed

no-load speed - full-load speed

no-load speed

⇒ For which of the following applications a D.C. motor is preferred over an A.C. motor ?
Low speed operation
High speed operation
Variable speed operation
Fixed speed operation

⇒ Which of the following motors, on removal of load, will run at the highest speed ?
Shunt motor
Series motor
Differential compound
Cumulative compound

⇒ At the instant of starting when a D.C. motor is put on supply, it behaves like
a highly resistive circuit
a low resistance circuit
a capacitive circuit
none of the above

⇒ When the armature of a D.C. motor rotates, e.m.f. induced is
self-induced e.m.f.
mutually induced e.m.f.
back e.m.f.
none of the above

⇒ Which D.C. motor will be preferred for machine tools ?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor