Question is ⇒ D.C. series motors are used, Options are ⇒ (A) where load is constant, (B) where load changes frequently, (C) where constant operating speed is needed, (D) in none of the above situations., (E) , Leave your comments or Download question paper.

Question is ⇒ D.C. series motors are used, Options are ⇒ (A) where load is constant, (B) where load changes frequently, (C) where constant operating speed is needed, (D) in none of the above situations., (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	D.C. series motors are used
A.	where load is constant [Wrong Answer]
B.	where load changes frequently [Wrong Answer]
C.	where constant operating speed is needed [Wrong Answer]
D.	in none of the above situations. [Correct Answer]
View Answer 7 -5 Explanation:- Answer : D Discuss it below : LiFE CHAnGer Said on 2020-05-17 11:52:07 high starting torque required !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ Field winding of a D.C. series motor is usually provided with thick wire
to provide large flux
to reduce the use of insulating materials
as it carries large load current
in order to reduce eddy current

⇒ A D.C. motor can be easily identified by
winding
commutator
size of conductor
yoke

⇒ Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
Providing laminations in armature core
Providing laminations in stator
Using non-magnetic material for frame
Using material of low hysteresis coefficient for armature core material

⇒ A brake test on D.C. motors is usually restricted to
small horse power motors
variable speed motors
high speed motors
open frame type motors.

⇒ For the same H.P. rating and full load speed, following motor has poor starting torque
shunt
series
differentially compounded
cumulatively compounded

⇒ Which motor should not be started on no-load ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor

⇒ Which of the following can be used to control the speed of a D.C. motor ?
Thermistor
Thyristor
Thyratron
Transistor

⇒ Which D.C. motor has got maximum self relieving property ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor

⇒ In a D.C. generator all of the following could be the effects of iron losses except
Loss of efficiency
Excessive heating of core
Increase in terminal voltage
Rise in temperature of ventilating air

⇒ D.C. shunt motors are used for driving
trains
cranes
hoists
machine tools

⇒ By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
Frame
Shaft
Commutator
Stator

⇒ Which one of the following is not the function of pole shoes in a D.C. machine ?
To reduce eddy current loss
To support the field coils
To spread out flux for better uniformity
To reduce the reluctance of the magnetic path

⇒ 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

⇒ In a D.C. shunt motor, speed is
independent of armature current
directly proportional to the armature current
proportional to the square of the current
inversely proportional to the armature current

⇒ The armature voltage control of D.C. motor provides
constant torque drive
constant voltage drive
constant current drive
none of the above

⇒ If a D.C. motor is connected across the A.C. supply it will
run at normal speed
not run
run at lower Speed
burn due to heat produced in the field winding by eddy currents

⇒ The type of D.C. motor used for shears and punches is
shunt motor.
series motor
differential compound D.C. motor
cumulative compound D.C. motor

⇒ In a motor, energy conversion would not have been possible but for the
production of opposing back e.m.f. Eb in the armature
input energy from supply
use of commutator
application of Fleming's left-hand rule

⇒ Which of the following motor is preferred for operation in highly explosive atmosphere ?
Series motor
Shunt motor
Air motor
Battery operated motor

⇒ Which D.C. motor has got maximum self loading property?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compotinded motor

⇒ The speed of a D.C. shunt motor can be increased by
increasing the resistance in armature circuit
increasing the resistance in field circuit
reducing the resistance in the field circuit
reducing the resistance in the armature circuit

⇒ Which loss in a D.C. generator does not vary with load as well as flux density ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ Which of the following load normally needs starting torque more than the rated torque?
Blowers
Conveyors
Air compressors
Centrifugal pumps

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

⇒ The speed of a D.C. shunt motor more than its full-load speed can be obtained by
decreasing the field current
increasing the field current
decreasing the armature current
increasing the armature current

⇒ 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

⇒ Speed control by the variation of flux, in a D.C. shunt motor, will give
constant torque drive
variable torque drive
constant power drive
variable power drive

⇒ The condition for maximum power in case of D.C. motor is
back e.m.f. = 2 x supply voltage
back e.m.f. = 1/2 x supply voltage
supply voltage = 1/2 x back e.m.f.
supply voltage = back e.m.f.

⇒ D.C. series motors are used
where load is constant
where load changes frequently
where constant operating speed is needed
in none of the above situations.

⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method
less expensive
less wasteful
suitable for rapidly changing loads
unsuitable for changing loads

high starting torque required