61.
As -the load is increased the speed of D.C. shunt motor will
A
reduce slightly
B
increase slightly
C
increase proportionately
D
remains unchanged
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121 practice sets · Page 4 of 7
As -the load is increased the speed of D.C. shunt motor will
reduce slightly
increase slightly
increase proportionately
remains unchanged
According to Flemings 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 aovtaat of conductor
resultant force on conductor
none of the above
A three point starter is considered suitable for
shunt motors
shunt as well as compound motors
shunt, compound and series motors
all D.C. motors
A direct on line starter is used: for starting motors
iip to 5 H.P.
up to 10 H.P.
up to 15 H.P.
up to 20 H.P.
A D.C. series motor is that which
has its field winding consisting of thick wire and less turns
has a poor torque
can be started easily without load
has almost constant speed
Why are the D.C. motors preferred for traction applications ?
Torque and speed are inversely proportional to armature current
Torque is proportional to armature current
Torque is proportional to square root of armature current
The speed is inversely proportional to the torque and the torque is proportional to square of armature current
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 unifor-mity
To reduce the reluctance of the mag-netic path
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors ?
Low cost
Wide speed range
Stability
High starting torque.
Which of the following tests will be suitable for testing two similar D.C. series motorsof large capacity ?
Swinburnes test
Hopkinsons test
Field test
Brake test
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 co-efficient for armature core material
Which of the following motors one will choose to drive the rotary compressor ?
D.C. shunt motor
D.C. series motor
Universal motor
Synchronous motor
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
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 motor has the poorest speed regulation ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor
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 losses are significantly reduced by laminating the core of aD.C. generator ?
Hysteresis losses
Eddy current losses
Copper losses
Windage losses
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
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
Which of the following load normally needs starting torque more than the rated torque?
Blowers
Conveyors
Air compressors
Centrifugal pumps