DMRC JE/SSC JE/CIL MT ELECTRICAL ENGINEERING IMPORTANT MCQ PART 9(DC MOTORS)

1.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
ANSWER : : compound motor
2.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
ANSWER : : drum type controller is used
3.D.C. generators are normally designed for maximum efficiency around
full-load
rated r.p.m.
rated voltage
all of the above
ANSWER : : full-load
4.The purpose of retardation test on D.C. shunt machines is to find out
stray losses
eddy current losses
field copper losses
windage losses
ANSWER : : stray losses
5.D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short
duration. We will select the
series motor
shunt motor
compound motor
any of the above
ANSWER : : series motor 

6.In variable speed motor
a stronger commutating field is needed at low speed than at high speed
a weaker commutating field is needed at low speed than at high speed
same commutating field is needed at low speed than at high speed
none of the above is correct
ANSWER : : a weaker commutating field is needed at low speed than at high speed
7.In the D.C. motor the iron losses occur in
the field
the armature
the brushes
the commutator
ANSWER : : the armature
8.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
also runs as a motor comes to stop after sometime
ANSWER : : runs as a generator
9.Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
Swinburne’s test
Hopkinson’s test
Field test
Brake test
ANSWER : : Field test
10.The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by
reducing the field current
decreasing the armature current
increasing the armature current
increasing the excitation current
ANSWER : : reducing the field current
11.If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
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
nothing will happen to motor
motor will come to stop
ANSWER : : this will make armature to take heavy current, possibly burning it
12.During rheostat braking of D.C. series motors
motor is run as a generator
motor is reversed in direction
motor is run at reduced speed
motor is run as a generator
ANSWER : motor is run as a generator
13.Hopkinson’s test on D.C. machines is conducted at
no-load
part load
full-load
overload
ANSWER : : full-load
14.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
ANSWER : : variable losses = constant losses
15.D.C. generators are installed near the load centres to reduce
iron losses
line losses
sparking
corona losses
ANSWER : : line losses 

16.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
ANSWER : : back e.m.f.
17.Which method of braking is generally used in elevators ?
Plugging
Regenerative braking
Rheostatic braking
None of the above
ANSWER : : Plugging
18.Which D.C. motor has got maximum self relieving property ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor
ANSWER : : Series motor
19.In a D.C. generator, the iron losses mainly take place in
yoke
commutator
armature conductors
armature rotor
ANSWER : : armature rotor

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DMRC JE/SSC JE/CIL MT ELECTRICAL ENGINEERING IMPORTANT MCQ PART 8(DC MOTORS)

One Response

  1. Anitha December 15, 2017

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