Question is ⇒ Which motor should be used for centrifugal pumps ?, Options are ⇒ (A) Series motor, (B) Shunt motor, (C) Either of the above, (D) None of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ Which motor should be used for centrifugal pumps ?, Options are ⇒ (A) Series motor, (B) Shunt motor, (C) Either of the above, (D) None of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Which motor should be used for centrifugal pumps ?
A.	Series motor [Wrong Answer]
B.	Shunt motor [Correct Answer]
C.	Either of the above [Wrong Answer]
D.	None of the above [Wrong Answer]
View Answer 8 -4 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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⇒ In a D.C. motor, unidirectional torque is produced with the help of
end plates
bushes
commutator
both (b) and (c)

⇒ 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.

⇒ During rheostatic braking the braking torque is proportional to
speed
(speed)²
(speed)^-1
(speed)^-2

⇒ In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
100% of the previous value
50% of the previous value
25% of the previous value
10% of the previous value

⇒ 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

⇒ Which motor has the poorest speed control?
Differentially compounded motor
Cumulatively compounded motor
Shunt motor
Series motor

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

⇒ In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
almost negligible
rated full-load current
less than full-load current
more than full-load current

⇒ Speed control by Ward Leonard method gives uniform speed variation
in one direction
in both directions
below normal speed only
above normal speed only

⇒ In a manual shunt motor starter
over load relay is connected in series and no volt relay in parallel with the load
over load relay is connected in parallel and no volt relay in series with the load
over load relay and no volt relay are both connected in series with the load
over load relay and no volt relay are both connected in parallel with the load

⇒ D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this
series motor
shunt motor
compound motor
any of the above

⇒ 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

⇒ If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will
decrease
increase
remain same
become zero

⇒ 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

⇒ Regenerative braking on D.C. shunt motors is used when
the load has overhauling characteristics
the load is variable
the load also acts as a braking force
the load is constantly decreasing

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

⇒ The armature shaft of a D.C. motor must be able to withstand
any unbalanced magnetic pull on the armature core
twisting strains due to transmission of torque
bending moment due to the weight of the armature and commutator
all of the above

⇒ The mechanical power developed by a D.C. motor is equal to
power input + losses
back e.m.f. X armature current
power output X losses
power output X efficiency

⇒ 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

⇒ A direct on line starter is used for starting motors
up to 5 H.P.
up to 10 H.P.
up to 15 H.P.
up to 20 H.P.

⇒ According to Fleming's left hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
current, in the conductor
movement of conductor
resultant force on conductor
none of the above

⇒ In case of a shunt motor if the supply voltage is increased by 10%, which of the following will decrease ?
full load current
full load speed
starting torque
none of the above

⇒ 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

⇒ No-load speed of which of the following motor will be highest ?
Shunt motor
Series motor
Cumulative compound motor
Differentiate compound motor

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

⇒ Which of the following methods is most ecoriomical fol. finding the no-load losses of a large b.C. shunt motor ?
Retardation test
Swinburne's test
Hopkinson's test
none of the above

⇒ 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

⇒ 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 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

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