Question is ⇒ For a D.C. shunt motor if the excitation is changed, Options are ⇒ (A) torque will remain constant, (B) torque will change but power will remain constant, (C) torque and power both will change, (D) torque, power and speed, all will change, (E) , Leave your comments or Download question paper.

Question is ⇒ For a D.C. shunt motor if the excitation is changed, Options are ⇒ (A) torque will remain constant, (B) torque will change but power will remain constant, (C) torque and power both will change, (D) torque, power and speed, all will change, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	For a D.C. shunt motor if the excitation is changed
A.	torque will remain constant [Wrong Answer]
B.	torque will change but power will remain constant [Correct Answer]
C.	torque and power both will change [Wrong Answer]
D.	torque, power and speed, all will change [Wrong Answer]
View Answer 5 -8 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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⇒ 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

⇒ Which D.C. motor Will have least percentage increase of input current for the same percentage increase in the torque?
Shunt motor
Series motor
Cumulative compound motor
Separately excited motor

⇒ The losses occurring in a D.C. generator are given below. Which loss is likely to have the least proportion ?
Magnetic losses
Armature copper losses
Mechanical losses
Field copper losses

⇒ A series motor is started without load. The effect is that
the back e.m.f. decreases
the torque increases rapidly
the speed increases rapidly
the current drawn increases rapidly

⇒ 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

⇒ When the electric train is moving down a hill the D.C. motor act as
D.C. series generator
D.C. shunt generator
D.C. shunt motor
D.C. series motor

⇒ In Field's test for series motors one motor drives the other machine as
cumulative compound generator
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⇒ Which D.C. motor will be preferred for machine tools ?
Series motor
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Cumulative compound motor
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⇒ 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

⇒ 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

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

⇒ 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 method of braking is generally used in elevators ?
Plugging
Regenerative braking
Rheostatic braking
None of the above

⇒ The current drawn by the armature of D.C. motor is directly proportional to
the torque required
the speed of the motor
the voltage across the terminals
none 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

⇒ A 230 V D.C. shlint motor takes 32 A at full load. The back e.m.f. on full load, if the resistance of motor armature and shunt field windings are 0.2 Ω and 115 Ω respectively, will be
210 V
215 V
220 V
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⇒ Which of the following motors one will choose to drive the rotary compressor ?
D.C. shunt motor
D.C. series motor
Universal motor
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⇒ Ward-Leonard system of speed control is not recommended for
very low speeds
frequent motor reversals
wide speed range
constant speed operation

⇒ As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit
a resistance is connected in series with armature
a resistance is connected parallel to the armature
armature is temporarily open circuited
a high value resistor is connected across the field winding

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

⇒ Which of the following loss in a D.C. generator varies significantly with the load current ?
Field copper loss
Windage loss
Armature copper loss
None of the above

⇒ The function of a field regulator for compound motors is to
control the flux
limit the armature current
demagnetise the field partially
none of the above

⇒ Voltage equation for D.C. motor is
Eb = V + IaRa
V = Eb + IaRa
Eb = V - Ia²Ra
V = Eb - IaRa

⇒ 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

⇒ The armature torque of the D.C. shunt motor is proportional to
field flux only
armature current only
both (a) and (b)
none of the above

⇒ As the load is increased the speed of D.C. shunt motor will
reduce slightly
increase slightly
increase proportionately -
remains unchanged

⇒ 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

⇒ Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of
D.C. series motor
D.C. shunt motor
induction motor
all of above motors

⇒ In an overloaded motor main danger arises due to
winding getting overheated
busbars getting heated
starter getting damaged
bearings getting overheated

⇒ Which loss in a D.C. generator varies with load ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss