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DC Motor Question & Answers

October 25, 2021 By Wat Electrical

This article lists 100 DC Motor MCQs for engineering students. All the DC Motor Questions & Answers given below includes solution and link wherever possible to the relevant topic.

Electrical motors are electrical energy conversion devices that are used mostly in all electrical systems. Motors are designed to convert electrical energy into mechanical energy. There are different types of motors based on their source and output power. A common category of motors is the AC motor and DC motor.

As compared to generators, its manufacturing is almost similar but they differ in their functioning. The principle followed by an electric motor is electricity and electromagnetism.

1). In DC motor, the speed of the motor is directly proportional to ?
HintThe motor speed mainly depends on back emf
2). In series, DC motor armature current is equal to?
HintThe armature current is equivalent to current at load
3). Commutators are used in---?
HintThese motors are called direct current motors
Please refer to this link to know more about Commutator
4). Which of the following is not a rotary part in the DC motor
HintOnce the current flows through the winding then the field flux can be generated
5). ---------law is used to detect the direction of rotation in the motor?
HintThis rule is used in DC motors
6). The residual magnetism of DC machines is---?
HintIt is under 4%
7). In DC motors with the change in supply voltage, the starting Torque-----
HintThe starting Torque will be stable
8). In DC motors, the full load current decreases with ------ supply voltage.
HintThe voltage supply will be enhanced
9). When high torque and wide speed ranges are required---------is used.
HintThis motor converts the energy from electrical to mechanical
10). In DC motors Torque depends on -----?
HintThe flow of current in the windings
Please refer to this link to know more about Torque & Power Equation
11). The resultant speed of the series DC motor is -----when connected in parallel.
HintAs compared to normal speed, it is high.
12). For high starting speed ------motor is used ?
HintThis motor is used where high starting torque is required.
13. At high Torque speed, the DC series motor is ?
HintThe speed of this motor is constant
14). Which of the following motor is used where an extensive range of control is required?
HintThese motors operate through direct current
15). In DC motor, the armature control voltage offers?
HintIt is used in compressors, mixers, conveyors, Hoists, etc.
16). In machine tools, which of the following type of DC motor is used?
HintThis motor is also called a shunt-wound motor
17). Which type of DC motor is used in elevators?
HintThis motor is used where high starting torque is necessary
18). If the back emf disappears in DC motor then….?
HintIt is a common component in dc machines
19). The starting torque used by the load is…?
HintThese are used to transport different materials from one place to another in industries
20). If the DC motor voltage supply is increased then….will be decreased?
HintIt is the large current of DC motor
21). What is the function of a starter in a DC motor?
HintIt decreases the beginning current
22). The resistance at the motor beginning is….?
HintThe beginning resistance is not high
Please refer to this link to know more about Resistance
23). In which of the following, high starting torque is used?
HintIt helps the locomotive to move from the stable position
24). Which of the following ranges of DC motors are operated through a DOL starter?
HintThis range of motor uses 2.3 kW of power
25). What is the function of a fractional pitch winding in a DC motor?
HintIt is used to decrease the sparking

DC Motor MCQs for Interviews

26). Who invented the first DC motor?
HintIt was invented in 1886
27). How many types of DC motors?
HintThey are series, shunt, and compound
28). Which type of DC motor has the utmost self-loading property?
HintThe flux of this motor reduces the main series winding effect because of the shunt field winding.
29). Which type of starter is used for both compound and shunt motors?
HintIt maintains the speed of a dc shunt motor
30). The speed regulation of the series motor is?
HintIts speed regulation is very less
31). When the applied voltage of a DC motor is changed then the motor speed will be…?
HintThe speed of the dc motor depends on different factors like the applied voltage, field current, etc.
32). The torque breaking provided by the plugging is?
HintPlugging provides maximum torque breaking in a motor.
33). The iron losses in the DC motor mainly occur within….?
HintIt is a common component in an electric machine
34). Which of the following part is available in DC motor?
HintCommutator provides mechanical rectification
35). Flemming's left-hand rules determine…?
HintIt is used to determine the motor direction
36). In the DC machine, the armature of eddy current is made with laminated sheets then….?
HintLamination sheets are used to reduce eddy current loss
37). In a DC motor, the induced EMF is…?
HintThe oscillation is smooth repetition
38). The armature resistance value within a DC motor is?
HintThis fraction can be written as 1/2
39). Which of the following is used to restrict the maximum torque in the DC motor?
HintIt is the method where the reversal current takes place.
40). Which of the following is the main reason to affect the DC motor speed?
HintThe current supplying throughout the moving motor
41). What is the function of a counter EMF in a DC motor?
HintThe energy within the motor can be changed
42). The uni-directional torque can be generated through….?
HintDue to the brushes as well as commutator, the torque can be produced.
43). Which motor is used in biomedical instruments?
HintThis motor is also called a brushless dc motor
44). When the load is increased within a differential compound DC motor, the speed will be….?
HintThe motor speed mainly depends on the connected load
45). In an extremely unstable environment, which of the following motor is used?
HintThis is also called pneumatic dynamic motor
46). A constant flux motor is also known as?
HintThis is also called a shunt wound DC motor
47). In which of the following DC motor, dynamic braking is used?
HintIt is a self-excited type DC motor
48). Once the armature reaction within a DC motor is increased then…?
HintThe flow of current through the windings
49). In which of the following application, DC shunt motor is used…?
HintThis machine is used for different operations like sanding, drilling, cutting, knurling, etc.
50). Which of the following device is used to change from AC to DC…?
HintBy using this, the direction of current will be changed within the coil

DC Motor MCQs for Exams

51). An alternate name of the motor rule is also called….?
HintThis rule is mainly used in motors
52). At which load, Hopkinson’s test is conducted on Motor?
HintThe highest current which is used to design a motor to carry under some conditions
53). The shape of the brush within the DC motor is?
HintElectrical contacts which are used to conduct current in between moving parts & stationary wires,
54). If we connect a DC motor across AC supply, then the motor will be….?
HintThe motor is damaged due to the generated heat within the field winding
55). If the load is reduced in a DC shunt motor, then the speed will be….?
HintThere is no change in the motor speed
56). Why DC motor is mostly preferred instead of AC?
HintBecause of the change is speed operation
57). The max self-loading property of the motor is…?
HintThe speed of this motor may be made almost constant
58). The material used to make commutators within a DC motor is?
HintThe chemical element of this material is Cu
59). The DC motor construction as compared to the DC generator is….?
HintFrame construction is different in DC motors & DC generators
60). In which direction, Ward Leonard method provides variation in speed…?
HintSpeed control can be done in both directions
61). Which of the following motor is used to drive the rotating compressor?
HintThis is one kind an AC motor
62). When the back emf of DC shunt motor increases…?
HintThe back emf of the motor depends on motor speed
63). A 3 point starter is used in which type of DC motor?
HintThis motor is also known as shunt wound dc motor
64). The starter handle of the DC motor must be moved like?
HintThe movement must be very flat without breaks
65). What is the function of a 4 point starter in a DC compound motor?
HintOnce the field current changes within Hold on coil then the effect of the flow of current will be reduced.
66). Which of the following is used as a motor controller?
HintIt is used to control an electrical circuit by turning ON/OFF
67). The armature copper loss in dc machine is also known as?
HintThese losses mainly occurs in field copper & armature windings
68). Iron losses in dc machines mainly occur?
HintIt is the rotating part in the dc machine
69). The essential component in the DC motor is?
HintIt is a mechanical rectifier
70). The order of the residual magnetism in DC motors is…?
HintIt ranges from >0<3
71). The self-relieving characteristic of the motor is…?
HintThe windings in this motor are connected in series
72). Once the DC motor armature turns then emf will be?
HintThis emf is quite opposite to the voltage applied
73). The test is used to test two same DC series motors with huge capacity is?
HintMainly used for electric traction works
74). Retardation test is mainly used in which type of motors?
HintThis test is also known as the running down test
75). What is the purpose of the Retardation test in DC machines?
HintThese are also known as circulating current losses

DC Motor MCQs for Quiz

76). The motor used in timers and signalling devices is…..?
HintThis kind of motor induces non-permanent magnetic poles over the ferromagnetic rotor
77). In refrigerators, which type of DC motor is used?
HintThese motors are available in two types like SRM & SynRM
78). In DC motor, the armature control voltage mainly provides…?
HintThese drives cause DC motors to draw fairly high current at less speed
79). The main benefit of DC motor as compared to AC is?
HintThe cost of a dc motor is less
80). What is the speed of a dc shunt motor when the load is increased?
HintIt decreases very less
81). If the voltage supply of dc motor is decreased then … will be increased?
HintIt is the highest current
82). As compared to rated torque, the starting torque is used by the load is….?
HintThese are used to move loads in industries
83). In a DC motor, the armature torque is high than the shaft torque because of……losses?
HintThis loss mainly occurs once the power loss acquires by windage when an object is rotated
84). How the rotation direction of a DC motor can be upturned?
HintOnce the supply terminals are interchanged, the direction of the motor can be changed
85). The principle of law used by DC motor is?
HintIt is the combination of two forces like electric and magnetic
86). If the flux within the field winding increases then the dc motor speed will be…?
HintBoth are opposite to each other
87). Flemmings left-hand rule is mainly applicable to……?
HintThe function of this device is quite opposite to generator
88). The motor’s standard direction is?
HintIt is also called counter clockwise direction
89). If the field is opened in DC shunt motor, then?
HintThe dc shunt motor speed will be high
90). The characterization of DC machines can be done through…?
HintThese are used in both motors and generators
91). All types of rotating machines are?
HintThe energy can be converted from electrical to mechanical
92). The structure of poles in?
HintIt has an alternating polarity
93). In a dc motor, the flow of current within a conductor is?
HintIt is alternating current
94). When a dc motor gets overheated?
HintWhen the motor gets too much load
95). The series field resistance as compared to shunt field is?
HintIt is quite opposite to the shunt field
96). When excessive motor vibration occurs?
HintIf we listen to a grating noise
97). Which type of dc motor is used to start heavy loads?
HintThis motor includes self-excited DC motors
98). When sparking occurs at the brushes?
HintSparking occurs mainly because of the dirt on the commutator
99). The shunt motor speed is practical…?
HintThe speed is stable practically
Please refer to this link to know more about DC shunt motor
100). For punch presses, which motor is used?
HintThese motors provide high starting torque
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