DC Motor Question & AnswersOctober 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 ? Rotor length Input power Back e.m.f. All of the above. HintThe motor speed mainly depends on back emf2). In series, DC motor armature current is equal to? Back e.m.f Load current Voltage Speed HintThe armature current is equivalent to current at load3). Commutators are used in---? DC motors AC motors Both a and b. None of the above. HintThese motors are called direct current motors Please refer to this link to know more about Commutator4). Which of the following is not a rotary part in the DC motor Rotor. Slip rings. Commutator. Field Winding. HintOnce the current flows through the winding then the field flux can be generated5). ---------law is used to detect the direction of rotation in the motor? Faraday law Columbus law Flemings left-hand rule Fleming's right-hand rule. HintThis rule is used in DC motors6). The residual magnetism of DC machines is---? 14 to 19 percent 6 to 10 percent 2 to 3 percent 1 to 2 percent. HintIt is under 4%7). In DC motors with the change in supply voltage, the starting Torque----- Increases Decreases Remains the same Equal to the supply voltage. HintThe starting Torque will be stable8). In DC motors, the full load current decreases with ------ supply voltage. Increased Decreased. Constant value of None of the above HintThe voltage supply will be enhanced9). When high torque and wide speed ranges are required---------is used. Induction motor. AC motor. DC motor All of the above. HintThis motor converts the energy from electrical to mechanical10). In DC motors Torque depends on -----? Armature current Back e.m.f. Speed Voltage. HintThe flow of current in the windings Please refer to this link to know more about Torque & Power Equation11). The resultant speed of the series DC motor is -----when connected in parallel. Decreases Zero Same as normal speed More than the normal speed. HintAs compared to normal speed, it is high.12). For high starting speed ------motor is used ? DC shunt motor Induction motor DC series motor. Both a and c. HintThis motor is used where high starting torque is required.13. At high Torque speed, the DC series motor is ? Increases Decreases. Remains Constant Zero. HintThe speed of this motor is constant14). Which of the following motor is used where an extensive range of control is required? AC Motor DC Motors Synchronous Motor Induction Motor HintThese motors operate through direct current15). In DC motor, the armature control voltage offers? Stable torque drive Stable current drive Stable voltage drive None of the above HintIt is used in compressors, mixers, conveyors, Hoists, etc.16). In machine tools, which of the following type of DC motor is used? Shunt motor Series motor Series wound Self-excited HintThis motor is also called a shunt-wound motor17). Which type of DC motor is used in elevators? Shunt motor DC cumulative compound motor Self-excited Series motor HintThis motor is used where high starting torque is necessary18). If the back emf disappears in DC motor then….? The armature may damage The motor stops working The motor generates noise sound Motor works very fast HintIt is a common component in dc machines19). The starting torque used by the load is…? Pumps Compressors Conveyors Blowers HintThese are used to transport different materials from one place to another in industries20). If the DC motor voltage supply is increased then….will be decreased? Full load current Starting torque Operating speed Efficiency HintIt is the large current of DC motor21). What is the function of a starter in a DC motor? It controls the motor speed It restricts the starting current for protecting It stops the motor It reduces the motor speed HintIt decreases the beginning current 22). The resistance at the motor beginning is….? High Low Medium Very high HintThe beginning resistance is not high Please refer to this link to know more about Resistance23). In which of the following, high starting torque is used? Air blower Locomotive Centrifugal pump Machines HintIt helps the locomotive to move from the stable position24). Which of the following ranges of DC motors are operated through a DOL starter? Up to 3 H.P. Up to 5 H.P. Up to 7 H.P. Up to 9 H.P. HintThis range of motor uses 2.3 kW of power 25). What is the function of a fractional pitch winding in a DC motor? To reduce heat To control sparks To enhance the e.m.f produces To enhance cooling HintIt is used to decrease the sparkingDC Motor MCQs for Interviews26). Who invented the first DC motor? William Marx William Sturgeon Thomas Davenport Antony HintIt was invented in 188627). How many types of DC motors? 2 3 4 5 HintThey are series, shunt, and compound28). Which type of DC motor has the utmost self-loading property? Self-excited Differentially compounded motor Series wound Shunt-wound 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? 2-point starter 3-point starter 4-point starter 5-point starter HintIt maintains the speed of a dc shunt motor 30). The speed regulation of the series motor is? Fast Poor Medium Stable HintIts speed regulation is very less31). When the applied voltage of a DC motor is changed then the motor speed will be…? Not changed Changed Stable Slightly changed 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? Low High Medium Null HintPlugging provides maximum torque breaking in a motor.33). The iron losses in the DC motor mainly occur within….? The armature The rotor The field The stator HintIt is a common component in an electric machine34). Which of the following part is available in DC motor? Stator Rotor Commutator Shaft HintCommutator provides mechanical rectification35). Flemming's left-hand rules determine…? The direction of Motor’s rotation Motor working Motor stability Mechanical strength HintIt is used to determine the motor direction36). In the DC machine, the armature of eddy current is made with laminated sheets then….? It decreases hysteresis loss It decreases armature copper loss It decreases eddy current loss d. anical strength HintLamination sheets are used to reduce eddy current loss37). In a DC motor, the induced EMF is…? Alternating Sinusoidal Square Triangle HintThe oscillation is smooth repetition38). The armature resistance value within a DC motor is? 1 0.5 5 10 HintThis fraction can be written as 1/239). Which of the following is used to restrict the maximum torque in the DC motor? Speed Heating Commutation Armature current 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? Back emf Flux Armature current Load HintThe current supplying throughout the moving motor41). What is the function of a counter EMF in a DC motor? Used for energy conversion Reduces motor speed Enhances motor speed To provide protection HintThe energy within the motor can be changed42). The uni-directional torque can be generated through….? Only brushes Stator Rotor Both commutator & brushes HintDue to the brushes as well as commutator, the torque can be produced.43). Which motor is used in biomedical instruments? PMDC motor BLDC motor DC shunt motor DC series motor HintThis motor is also called a brushless dc motor44). When the load is increased within a differential compound DC motor, the speed will be….? Stable Increased Decreased Motor will damage HintThe motor speed mainly depends on the connected load45). In an extremely unstable environment, which of the following motor is used? BLDC Series PMDC Air Motor HintThis is also called pneumatic dynamic motor46). A constant flux motor is also known as? DC shunt motor Air Motor Constant voltage motor Variable current motor HintThis is also called a shunt wound DC motor47). In which of the following DC motor, dynamic braking is used? DC shunt motor Variable current motor Constant voltage motor Air Motor HintIt is a self-excited type DC motor48). Once the armature reaction within a DC motor is increased then…? Armature current will be increased Decreases field current Armature current will be decreased Increases field current HintThe flow of current through the windings49). In which of the following application, DC shunt motor is used…? Cranes Elevators Lathe Machines Electric Traction 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…? Windings Armature Split rings Bearings HintBy using this, the direction of current will be changed within the coilDC Motor MCQs for Exams51). An alternate name of the motor rule is also called….? Flemmings right-hand rule Flemming’s left-hand rule Flemming’s right-hand thumb rule Flemming’s left-hand thumb rule HintThis rule is mainly used in motors52). At which load, Hopkinson’s test is conducted on Motor? Overload Part load No-load Full load HintThe highest current which is used to design a motor to carry under some conditions53). The shape of the brush within the DC motor is? Square Cylindrical Rectangular Triangle 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….? It will not work Damages Speed will be reduced Works efficiently HintThe motor is damaged due to the generated heat within the field winding55). If the load is reduced in a DC shunt motor, then the speed will be….? Increased Reduced Stable None of the above HintThere is no change in the motor speed56). Why DC motor is mostly preferred instead of AC? Speed operation is low Speed operation is stable Speed operation is high Speed operation is variable HintBecause of the change is speed operation57). The max self-loading property of the motor is…? Air Motor Constant voltage motor DC shunt motor Differentially compound motor HintThe speed of this motor may be made almost constant 58). The material used to make commutators within a DC motor is? Copper Caste Iron Silver Silicon Steel HintThe chemical element of this material is Cu59). The DC motor construction as compared to the DC generator is….? Same Different Same except frame construction Stable HintFrame construction is different in DC motors & DC generators60). In which direction, Ward Leonard method provides variation in speed…? In one direction In two directions In three directions Under normal speed HintSpeed control can be done in both directions61). Which of the following motor is used to drive the rotating compressor? Synchronous Asynchronous DC series motor DC shunt motor HintThis is one kind an AC motor62). When the back emf of DC shunt motor increases…? If the motor speed is increased If the motor speed is decreased There is no change in motor speed It becomes zero HintThe back emf of the motor depends on motor speed63). A 3 point starter is used in which type of DC motor? Series motor Compound motor Shunt motor Air motor HintThis motor is also known as shunt wound dc motor64). The starter handle of the DC motor must be moved like? Quickly Slowly Smoothly With jerking HintThe movement must be very flat without breaks65). What is the function of a 4 point starter in a DC compound motor? Increases the field current Decreases the field current Stops the flow of current Reduces the effect of current flow in Hold ON coil 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? Relay Toggle switch Transformer Drum switch HintIt is used to control an electrical circuit by turning ON/OFF67). The armature copper loss in dc machine is also known as? Variable loss Windage loss Friction loss Iron loss HintThese losses mainly occurs in field copper & armature windings68). Iron losses in dc machines mainly occur? Windings Armature core Yoke Brushes HintIt is the rotating part in the dc machine69). The essential component in the DC motor is? Rotor Stator Frame Commutator HintIt is a mechanical rectifier70). The order of the residual magnetism in DC motors is…? 1 to 2% 1 to 3% 2 to 3% 4 to 5% HintIt ranges from >0<371). The self-relieving characteristic of the motor is…? Shunt motor Series motor Air motor Self-excited HintThe windings in this motor are connected in series72). Once the DC motor armature turns then emf will be? Induced emf Back emf Mutually induced Self-induced HintThis emf is quite opposite to the voltage applied73). The test is used to test two same DC series motors with huge capacity is? Brake test Field test Swinburne's test Hopkin’s test HintMainly used for electric traction works74). Retardation test is mainly used in which type of motors? DC series motor DC shunt motor Self-excited motor Air motor HintThis test is also known as the running down test75). What is the purpose of the Retardation test in DC machines? Find out stray losses Find out windage losses Find out field copper losses Find out copper losses HintThese are also known as circulating current lossesDC Motor MCQs for Quiz76). The motor used in timers and signalling devices is…..? Air motor Reluctance motor Series motor Synchronous motor HintThis kind of motor induces non-permanent magnetic poles over the ferromagnetic rotor77). In refrigerators, which type of DC motor is used? Reluctance motor Series motor Air motor Synchronous motor HintThese motors are available in two types like SRM & SynRM78). In DC motor, the armature control voltage mainly provides…? Stable voltage drive Stable torque drive Stable current drive Changing voltage drive 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? Stable Speed range is wide Not expensive Less weight HintThe cost of a dc motor is less80). What is the speed of a dc shunt motor when the load is increased? Slightly decreased Maximum decreased Increases Slightly increases HintIt decreases very less81). If the voltage supply of dc motor is decreased then … will be increased? Full load current Load increased Starting torque Operating speed HintIt is the highest current82). As compared to rated torque, the starting torque is used by the load is….? Conveyors Air compressors Blowers Pumps HintThese are used to move loads in industries83). In a DC motor, the armature torque is high than the shaft torque because of……losses? Rotational Mechanical Back emf Copper HintThis loss mainly occurs once the power loss acquires by windage when an object is rotated84). How the rotation direction of a DC motor can be upturned? By interchanging the supply terminals By shortening the supply terminals By interchanging the field terminals By shortening the field terminals HintOnce the supply terminals are interchanged, the direction of the motor can be changed85). The principle of law used by DC motor is? Flemmings Law Lorentz Law Faradays Law Boltzman law HintIt is the combination of two forces like electric and magnetic86). If the flux within the field winding increases then the dc motor speed will be…? Increases Decreases Constant Not stable HintBoth are opposite to each other87). Flemmings left-hand rule is mainly applicable to……? Generator Motor Transformer Inductor HintThe function of this device is quite opposite to generator88). The motor’s standard direction is? Clockwise Anti clock wise In both directions Constant HintIt is also called counter clockwise direction89). If the field is opened in DC shunt motor, then? Motor speed will be maximum Armature current will be increased Motor speed will be low Armature current will be reduced HintThe dc shunt motor speed will be high90). The characterization of DC machines can be done through…? Armatures Brushes Commutator Rotor HintThese are used in both motors and generators91). All types of rotating machines are? AC machines DC machines Heat converters Electromechanical converters HintThe energy can be converted from electrical to mechanical92). The structure of poles in? Horseshoe Hetro polar Circle Square HintIt has an alternating polarity93). In a dc motor, the flow of current within a conductor is? AC DC Transient Both HintIt is alternating current94). When a dc motor gets overheated? Overloads Nonstop working Loose parts Open armature coil HintWhen the motor gets too much load95). The series field resistance as compared to shunt field is? Low High Infinite Stable HintIt is quite opposite to the shunt field96). When excessive motor vibration occurs? Overload When a shaft is bent Worn bearings The armature coil is open HintIf we listen to a grating noise97). Which type of dc motor is used to start heavy loads? Air motor Self-excited Series motor Shunt motor HintThis motor includes self-excited DC motors98). When sparking occurs at the brushes? Due to dust on the commutator Loose connections Worn bearings Heavy loads HintSparking occurs mainly because of the dirt on the commutator99). The shunt motor speed is practical…? Constant Increases Decreases No change HintThe speed is stable practically Please refer to this link to know more about DC shunt motor100). For punch presses, which motor is used? Cumulatively compounded Air motor Series motor Differentially compounded HintThese motors provide high starting torque Time is Up! Time's up
