Question is ⇒ Voltage equation for D.C. motor is, Options are ⇒ (A) Eb = V + IaRa, (B) V = Eb + IaRa, (C) Eb = V - Ia<sup>2</sup>Ra, (D) V = Eb - IaRa, (E) , Leave your comments or Download question paper.

Question is ⇒ Voltage equation for D.C. motor is, Options are ⇒ (A) Eb = V + IaRa, (B) V = Eb + IaRa, (C) Eb = V - Ia<sup>2</sup>Ra, (D) V = Eb - IaRa, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Voltage equation for D.C. motor is
A.	Eb = V + IaRa [Wrong Answer]
B.	V = Eb + IaRa [Correct Answer]
C.	Eb = V - Ia²Ra [Wrong Answer]
D.	V = Eb - IaRa [Wrong Answer]
View Answer 7 -6 Explanation:- Answer : B 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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⇒ 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 application a D.C. motor is preferred over an A.C. motor ?
High speed operation
Low speed operation
Fixed speed operation
Variable speed operation

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

⇒ In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
back e.m.f. is equal to armature drop
armature drop is negligible
flux is proportional to armature current
flux is practically constant in ac. shunt motors

⇒ When the speed of a D.C. motor increases
back e.m.f. increases and current drawn decreases
back e.m.f. as well as current drawn both increase
back e.m.f. as well as current drawn both decrease
back e.m.f. decreases and current drawn increases

⇒ The operation of electric generators and motors depend on the interaction between magnetic field and
copper conductors
electric field
electric current
commutator

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

⇒ For which types of D.C. motor, dynamic braking is generally used ?
Shunt motors
Series motors
Compound motors
All of the above

⇒ In a differentially compounded D.C. motor, if shunt field suddenly opens
the motor will first stop and then run in opposite direction as series motor
the motor will work as series motor and run at slow speed in the same direction
the motor will work as series motor and run at high speed in the same direction
the motor will not work and come to stop

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

⇒ 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.

⇒ Which D.C. motor is generally preferred for cranes and hoists ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor

⇒ Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control
drum type controller is used
three point starter is used
four point starter is used
all above can be used

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

⇒ 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

⇒ D.C. series machine has field consisting of
many number of turns of thick wire
many number of turns of thin wire
few number of turns of thick wire
few number of turns of thin wire

⇒ 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

⇒ 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

⇒ Speed ,control by varying the armature circuit resistance, in a D.C. motor, provides a
constant torque drive
variable torque drive
constant power drive
variable power drive

⇒ The condition for maximum efficiency for a D.C. generator is
eddy current losses = stray losses
hysteresis losses = eddy current losses
copper losses = 0
variable losses = constant losses

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

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

⇒ One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven
runs as a generator
does not run as a generator
also runs as a motor
comes to stop after sometime

⇒ 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 speed of a D.C. motor, under constant load conditions, is affected by
back e.m.f.
field flux
armature current
none of the above

⇒ If the field circuit of a loaded shunt motor is suddenly opened
torque developed by the motor would be reduced to zero
it would race to almost infinite speed
it would draw abnormally high armature current
the fuse or circuit breaker will open the circuit before too much damage is done to the motor

⇒ 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

⇒ Which of the following, in a D.C. motor, can sustain the maximum temperature rise ?
Commutator
Armature windings
Slip rings
Field windings

⇒ Which of the following loss in a D.C. generator is dissipated in the form of heat ?
Mechanical loss
Core loss
Copper loss
All of the above

⇒ 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