D.C Motors Mcqs – (Electrical Engineering) MCQs Latest For FPSC, PPSC, NTS, KPPSC, SPSC & Other Tests
“ D.C Motors Mcqs “. Tab this page to check “Latest D.C Motors MCQs” for the preparation of competitive mcqs, FPSC mcqs, PPSC mcqs, SPSC mcqs, KPPSC mcqs, AJKPSC mcqs, BPSC mcqs, NTS mcqs, PTS mcqs, OTS mcqs, Atomic Energy mcqs, Pak Army mcqs, Pak Navy mcqs, CTS mcqs, ETEA mcqs and others. The most occurred mcqs of D.C Motors in past papers. Past papers of D.C Motors mcqs. Past papers of D.C Motors MCQs. D.C Motors Mcqs are the necessary part of any competitive / job related exams. The D.C Motors mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related D.C Motors mcqs. The Important series of D.C Motors Mcqs are given below:
The speed of a D.C. shunt motor can be increased by_______________?
A. reducing the resistance in the field circuit
B. increasing the resistance in field circuit
C. increasing the resistance in armature circuit
D. reducing the resistance in the armature circuit
If I2 be the armature current, then speed of a D.C. shunt motor is_______________?
A. independent of Ia
B. varies as (Ia)
C. proportional to la
D. varies as la
Which motor has the poorest speed control?
A. Cumulatively compounded motor
B. Differentially compounded motor
C. Shunt motor
D. Series motor
For a D.C. shunt motor if the excitation is changed_______________?
A. torque and power both will change
B. torque will change but power will remain constant
C. torque will remain constant
D. torque, power and speed, all will change
The plugging gives the____________?
A. smallest torque braking
B. zero torque braking
C. highest torque braking
D. none of the above
The armature voltage control of D.C. motor provides_____________?
A. constant current drive
B. constant voltage drive
C. constant torque drive
D. none of the above
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor_____________?
A. of higher H.P. should be selected
B. of lower H.P. should be selected
C. can be used for 50°C ambient temperature also
D. is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor
If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking?
A. dynamic braking
B. plugging
C. regenerative
D. none of the above
E. any of the above
Which of the following motors one will choose to drive the rotary compressor ?
A. D.C. series motor
B. D.C. shunt motor
C. Universal motor
D. Synchronous motor
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will_________?
A. increase
B. remain same
C. decrease
D. become zero
Why are the D.C. motors preferred for traction applications ?
A. Torque is proportional to armature current
B. Torque and speed are inversely proportional to armature current
C. Torque is proportional to square root of armature current
D. The speed is inversely proportional to the torque and the torque is proportional to square of armature current
Which of the following motors is usually used in house-hold refrigerators ?
A. D.C. shunt motor
B. D.C. series motor
C. Single phase induction motor (split phase start or induction run motor)
D. Synchronous motor
E. Reluctance motor
Which of the following motors is most suitable for signalling devices and many kinds of timers ?
A. D.C. series motor
B. D.C. shunt motor
C. Induction motor
D. Reluctance motor
Which motor should not be started on no-load ?
A. Series motor
B. Cumulatively compounded motor
C. Shunt motor
D. Differentially compounded motor
Ward-Leonard control is basically a____________?
A. voltage control method
B. field control method
C. field divertor method
D. armature resistance control method
For constant torque drive which speed control method is preferred ?
A. Shunt armature control
B. Armature voltage control
C. Field control
D. Mechanical loading system
In Ward-Leonard control the lower limit of speed is imposed by________?
A. residual magnetism of the generator
B. mechanical losses of motor and generator together
C. core losses of motor
D. all of the above
The main disadvantage of the Ward-Leonard control method is______________?
A. high maintenance cost
B. high initial cost
C. low efficiency at Hght loads
D. all of the above
Regenerative method of braking is based on that___________?
A. back e.m.f. of rotor is more than the applied voltage
B. back e.m.f. is equal to the applied voltage
C. back e.m.f. is less than the applied voltage
D. none of the above
The hysteresis loss in a D.C. machine least depends on____________?
A. Maximum value of flux density
B. Frequency of magnetic reversals
C. Volume and grade of iron
D. Rate of flow of ventilating air
D.C Motors Mcqs
In a D.C. generator all of the following could be the effects of iron losses except___________?
A. Excessive heating of core
B. Loss of efficiency
C. Increase in terminal voltage
D. Rise in temperature of ventilating air
The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?
A. field copper loss
B. hysteresis loss
C. armature copper loss
D. eddy current loss
Which of the following loss in a D.C. generator varies significantly with the load current ?
A. Windage loss
B. Field copper loss
C. Armature copper loss
D. None of the above
Torque developed by a D.C. motor depends upon_____________?
A. active length of the conductor
B. magnetic field
C. current flow through the conductors
D. number of conductors
E. radius of armature
F. all above factors
D.C. shunt motors are used for driving____________?
A. cranes
B. trains
C. hoists
D. machine tools
In a manual shunt motor starter?
A. over load relay is connected in series and no volt relay in parallel with the load
B. over load relay and no volt relay are both connected in series with the load
C. over load relay is connected in parallel and no volt relay in series with the load
D. over load relay and no volt relay are both connected in parallel with the load
Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
A. Providing laminations in stator
B. Providing laminations in armature core
C. Using non-magnetic material for frame
D. Using material of low hysteresis co-efficient for armature core material
Which of the following loss in a D.C. generator is dissipated in the form of heat?
A. Core loss
B. Mechanical loss
C. Copper loss
D. All of the above
Which of the following losses are significantly reduced by laminating the core of a D.C. generator ?
A. Copper losses
B. Eddy current losses
C. Hysteresis losses
D. Windage losses
The total losses in a well designed D.C. generator of 10 kW will be nearly______________?
A. 1000 W
B. 500 W
C. 100 W
D. 1500 W
The condition for maximum efficiency for a D.C. generator is______________?
A. copper losses = 0
B. hysteresis losses = eddy current losses
C. eddy current losses = stray losses
D. variable losses = constant losses
D.C. generators are normally designed for maximum efficiency around_____________?
A. full-load
B. rated voltage
C. rated r.p.m.
D. all of the above
In a D.C. generator, the iron losses mainly take place in___________
A. commutator
B. yoke
C. armature conductors
D. armature rotor
D.C. generators are installed near the load centres to reduce_____________?
A. sparking
B. line losses
C. iron losses
D. corona losses
The purpose of retardation test on D.C. shunt machines is to find out____________?
A. stray losses
B. field copper losses
C. eddy current losses
D. windage losses
Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
A. Hopkinson’s test
B. Swinburne’s test
C. Field test
D. Brake test
Hopkinson’s test on D.C. machines is conducted at_______________?
A. part load
B. no-load
C. full-load
D. overload
During rheostat braking of D.C. series motors_____________?
A. motor is run as a generator
B. motor is run at reduced speed
C. motor is reversed in direction
For which types of D.C. motor, dynamic braking is generally used ?
A. Series motors
B. Shunt motors
C. Compound motors
D. All of the above
Which method of braking is generally used in elevators ?
A. Plugging
B. Rheostatic braking
C. Regenerative braking
D. None of the above
In variable speed motor___________?
A. same commutating field is needed at low speed than at high speed
B. a weaker commutating field is needed at low speed than at high speed
C. a stronger commutating field is needed at low speed than at high speed
D. none of the above is correct
When the armature of a D.C. motor rotates, e.m.f. induced is___________?
A. mutually induced e.m.f.
B. self-induced e.m.f.
C. back e.m.f
D. none of the above
Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?
A. drum type controller is used
B. four point starter is used
C. three point starter is used
D. all above can be used
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?
A. this will make armature to take heavy current, possibly burning it
B. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
C. motor will come to stop
D. nothing will happen to motor
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________________?
A. series motor
B. compound motor
C. shunt motor
D. any of the above
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______________?
A. shunt motor
B. series motor
C. compound motor
D. any of the above
Which D.C. motor has got maximum self relieving property ?
A. Series motor
B. Cumulatively compounded motor
C. Shunt motor
D. Differentially compounded motor
In the D.C. motor the iron losses occur in____________?
A. the brushes
B. the armature
C. the field
D. the commutator
The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by______________?
A. reducing the field current
B. increasing the armature current
C. decreasing the armature current
D. increasing the excitation current
E. none of the above methods
One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven_______________?
A. runs as a generator
B. also runs as a motor comes to stop after sometime
C. does not run as a generator
If the load on a DC shunt motor is increases, its speed is slightly reduced due to______________?
A. increase in flux
B. increase in armature current
C. decrease in reactance
D. decrease in back emf
In which of the following device the generated emf and armature current are in the opposite directions?
A. transformer
B. dc motor
C. dc generator
D. all of the above
With the increase in temperature, the speed of DC shunt motor____________?
A. remain same
B. increases
C. decreases.
D. none of the above
With the increase in temperature, the speed of DC series motor______________?
A. decreases
B. remain same
C. increases
D. none of the above
If the field winding resistance of a DC shunt motor is increases, its speed will____________?
A. remains same
B. increases
C. decreases
D. none of the above
Which of the following method is used for the speed control of DC shunt motor?
A. flux control method
B. voltage control method
C. rheostat control method
D. all of the above
A dc series motor should not be started on no load because it would___________?
A. fail to start without load
B. not develop starting torque
C. run at dangerously high speed
D. draw more current without producing sufficient torque
In a DC motor the inter-pole winding is connected in________________?
A. parallel big field winding
B. series speed armature winding
C. series with field winding
D. parallel with armature winding
Armature reaction in dc motor results___________?
A. short circuit
B. increase in speed
C. decrease in speed
D. open circuit
Which of the following test can be performed on DC series motor?
A. Hopkinson test
B. Swinburne test
C. Brake test
D. Field test
Ward Leonard method of speed control is basically a______________?
A. field diverter
B. armature controlled method
C. field control method
D. frequency control method