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 lengthInput powerBack e.m.f.All of the above.HintThe motor speed mainly depends on back emf 2). In series, DC motor armature current is equal to?Back e.m.fLoad currentVoltageSpeedHintThe armature current is equivalent to current at load 3). Commutators are used in---?DC motorsAC motorsBoth a and b.None of the above.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 motorRotor.Slip rings.Commutator.Field Winding.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?Faraday lawColumbus lawFlemings left-hand ruleFleming's right-hand rule.HintThis rule is used in DC motors 6). The residual magnetism of DC machines is---?14 to 19 percent6 to 10 percent2 to 3 percent1 to 2 percent.HintIt is under 4% 7). In DC motors with the change in supply voltage, the starting Torque-----IncreasesDecreasesRemains the sameEqual to the supply voltage.HintThe starting Torque will be stable 8). In DC motors, the full load current decreases with ------ supply voltage.IncreasedDecreased.Constant value ofNone of the aboveHintThe voltage supply will be enhanced 9). When high torque and wide speed ranges are required---------is used.Induction motor.AC motor.DC motorAll of the above.HintThis motor converts the energy from electrical to mechanical 10). In DC motors Torque depends on -----?Armature currentBack e.m.f.SpeedVoltage.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.DecreasesZeroSame as normal speedMore than the normal speed.HintAs compared to normal speed, it is high. 12). For high starting speed ------motor is used ?DC shunt motorInduction motorDC 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 ?IncreasesDecreases.Remains ConstantZero.HintThe speed of this motor is constant 14). Which of the following motor is used where an extensive range of control is required?AC MotorDC MotorsSynchronous MotorInduction MotorHintThese motors operate through direct current 15). In DC motor, the armature control voltage offers?Stable torque driveStable current driveStable voltage driveNone of the aboveHintIt is used in compressors, mixers, conveyors, Hoists, etc. 16). In machine tools, which of the following type of DC motor is used?Shunt motorSeries motorSeries woundSelf-excitedHintThis motor is also called a shunt-wound motor 17). Which type of DC motor is used in elevators?Shunt motorDC cumulative compound motorSelf-excitedSeries motorHintThis motor is used where high starting torque is necessary 18). If the back emf disappears in DC motor then….?The armature may damageThe motor stops workingThe motor generates noise soundMotor works very fastHintIt is a common component in dc machines 19). The starting torque used by the load is…?PumpsCompressorsConveyorsBlowersHintThese 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?Full load currentStarting torqueOperating speedEfficiencyHintIt is the large current of DC motor 21). What is the function of a starter in a DC motor?It controls the motor speedIt restricts the starting current for protectingIt stops the motorIt reduces the motor speedHintIt decreases the beginning current 22). The resistance at the motor beginning is….?HighLowMediumVery highHintThe 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?Air blowerLocomotiveCentrifugal pumpMachinesHintIt helps the locomotive to move from the stable position 24). 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 heatTo control sparksTo enhance the e.m.f producesTo enhance coolingHintIt is used to decrease the sparkingDC Motor MCQs for Interviews 26). Who invented the first DC motor?William MarxWilliam SturgeonThomas DavenportAntonyHintIt was invented in 1886 27). How many types of DC motors?2345HintThey are series, shunt, and compound 28). Which type of DC motor has the utmost self-loading property?Self-excitedDifferentially compounded motorSeries woundShunt-woundHintThe 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 starter3-point starter4-point starter5-point starterHintIt maintains the speed of a dc shunt motor 30). The speed regulation of the series motor is?FastPoorMediumStableHintIts speed regulation is very less 31). When the applied voltage of a DC motor is changed then the motor speed will be…?Not changedChangedStableSlightly changedHintThe 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?LowHighMediumNullHintPlugging provides maximum torque breaking in a motor. 33). The iron losses in the DC motor mainly occur within….?The armatureThe rotorThe fieldThe statorHintIt is a common component in an electric machine 34). Which of the following part is available in DC motor?StatorRotorCommutatorShaftHintCommutator provides mechanical rectification 35). Flemming's left-hand rules determine…?The direction of Motor’s rotationMotor workingMotor stabilityMechanical strengthHintIt is used to determine the motor direction 36). In the DC machine, the armature of eddy current is made with laminated sheets then….?It decreases hysteresis lossIt decreases armature copper lossIt decreases eddy current lossd. anical strengthHintLamination sheets are used to reduce eddy current loss 37). In a DC motor, the induced EMF is…?AlternatingSinusoidalSquareTriangleHintThe oscillation is smooth repetition 38). The armature resistance value within a DC motor is?10.5510HintThis fraction can be written as 1/2 39). Which of the following is used to restrict the maximum torque in the DC motor?SpeedHeatingCommutationArmature currentHintIt 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 emfFluxArmature currentLoadHintThe current supplying throughout the moving motor 41). What is the function of a counter EMF in a DC motor?Used for energy conversionReduces motor speedEnhances motor speedTo provide protectionHintThe energy within the motor can be changed 42). The uni-directional torque can be generated through….?Only brushesStatorRotorBoth commutator & brushesHintDue to the brushes as well as commutator, the torque can be produced. 43). Which motor is used in biomedical instruments?PMDC motorBLDC motorDC shunt motorDC series motorHintThis motor is also called a brushless dc motor 44). When the load is increased within a differential compound DC motor, the speed will be….?StableIncreasedDecreasedMotor will damageHintThe motor speed mainly depends on the connected load 45). In an extremely unstable environment, which of the following motor is used?BLDCSeriesPMDCAir MotorHintThis is also called pneumatic dynamic motor 46). A constant flux motor is also known as?DC shunt motorAir MotorConstant voltage motorVariable current motorHintThis is also called a shunt wound DC motor 47). In which of the following DC motor, dynamic braking is used?DC shunt motorVariable current motorConstant voltage motorAir MotorHintIt is a self-excited type DC motor 48). Once the armature reaction within a DC motor is increased then…?Armature current will be increasedDecreases field currentArmature current will be decreasedIncreases field currentHintThe flow of current through the windings 49). In which of the following application, DC shunt motor is used…?CranesElevatorsLathe MachinesElectric TractionHintThis 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…?WindingsArmatureSplit ringsBearingsHintBy using this, the direction of current will be changed within the coilDC Motor MCQs for Exams 51). An alternate name of the motor rule is also called….?Flemmings right-hand ruleFlemming’s left-hand ruleFlemming’s right-hand thumb ruleFlemming’s left-hand thumb ruleHintThis rule is mainly used in motors 52). At which load, Hopkinson’s test is conducted on Motor?OverloadPart loadNo-loadFull loadHintThe 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?SquareCylindricalRectangularTriangleHintElectrical 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 workDamagesSpeed will be reducedWorks efficientlyHintThe 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….?IncreasedReducedStableNone of the aboveHintThere is no change in the motor speed 56). Why DC motor is mostly preferred instead of AC?Speed operation is lowSpeed operation is stableSpeed operation is highSpeed operation is variableHintBecause of the change is speed operation 57). The max self-loading property of the motor is…?Air MotorConstant voltage motorDC shunt motorDifferentially compound motorHintThe speed of this motor may be made almost constant 58). The material used to make commutators within a DC motor is?CopperCaste IronSilverSilicon SteelHintThe chemical element of this material is Cu 59). The DC motor construction as compared to the DC generator is….?SameDifferentSame except frame constructionStableHintFrame construction is different in DC motors & DC generators 60). In which direction, Ward Leonard method provides variation in speed…?In one directionIn two directionsIn three directionsUnder normal speedHintSpeed control can be done in both directions 61). Which of the following motor is used to drive the rotating compressor?SynchronousAsynchronousDC series motorDC shunt motorHintThis is one kind an AC motor 62). When the back emf of DC shunt motor increases…?If the motor speed is increasedIf the motor speed is decreasedThere is no change in motor speedIt becomes zeroHintThe back emf of the motor depends on motor speed 63). A 3 point starter is used in which type of DC motor?Series motorCompound motorShunt motorAir motorHintThis motor is also known as shunt wound dc motor 64). The starter handle of the DC motor must be moved like?QuicklySlowlySmoothlyWith jerkingHintThe movement must be very flat without breaks 65). What is the function of a 4 point starter in a DC compound motor?Increases the field currentDecreases the field currentStops the flow of currentReduces the effect of current flow in Hold ON coilHintOnce 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?RelayToggle switchTransformerDrum switchHintIt is used to control an electrical circuit by turning ON/OFF 67). The armature copper loss in dc machine is also known as?Variable lossWindage lossFriction lossIron lossHintThese losses mainly occurs in field copper & armature windings 68). Iron losses in dc machines mainly occur?WindingsArmature coreYokeBrushesHintIt is the rotating part in the dc machine 69). The essential component in the DC motor is?RotorStatorFrameCommutatorHintIt is a mechanical rectifier 70). 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<3 71). The self-relieving characteristic of the motor is…?Shunt motorSeries motorAir motorSelf-excitedHintThe windings in this motor are connected in series 72). Once the DC motor armature turns then emf will be?Induced emfBack emfMutually inducedSelf-inducedHintThis emf is quite opposite to the voltage applied 73). The test is used to test two same DC series motors with huge capacity is?Brake testField testSwinburne's testHopkin’s testHintMainly used for electric traction works 74). Retardation test is mainly used in which type of motors?DC series motorDC shunt motorSelf-excited motorAir motorHintThis test is also known as the running down test 75). What is the purpose of the Retardation test in DC machines?Find out stray lossesFind out windage lossesFind out field copper lossesFind out copper lossesHintThese are also known as circulating current lossesDC Motor MCQs for Quiz 76). The motor used in timers and signalling devices is…..?Air motorReluctance motorSeries motorSynchronous motorHintThis kind of motor induces non-permanent magnetic poles over the ferromagnetic rotor 77). In refrigerators, which type of DC motor is used?Reluctance motorSeries motorAir motorSynchronous motorHintThese motors are available in two types like SRM & SynRM 78). In DC motor, the armature control voltage mainly provides…?Stable voltage driveStable torque driveStable current driveChanging voltage driveHintThese drives cause DC motors to draw fairly high current at less speed 79). The main benefit of DC motor as compared to AC is?StableSpeed range is wideNot expensiveLess weightHintThe cost of a dc motor is less 80). What is the speed of a dc shunt motor when the load is increased?Slightly decreasedMaximum decreasedIncreasesSlightly increasesHintIt decreases very less 81). If the voltage supply of dc motor is decreased then … will be increased?Full load currentLoad increasedStarting torqueOperating speedHintIt is the highest current 82). As compared to rated torque, the starting torque is used by the load is….?ConveyorsAir compressorsBlowersPumpsHintThese are used to move loads in industries 83). In a DC motor, the armature torque is high than the shaft torque because of……losses?RotationalMechanicalBack emfCopperHintThis 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?By interchanging the supply terminalsBy shortening the supply terminalsBy interchanging the field terminalsBy shortening the field terminalsHintOnce the supply terminals are interchanged, the direction of the motor can be changed 85). The principle of law used by DC motor is?Flemmings LawLorentz LawFaradays LawBoltzman lawHintIt 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…?IncreasesDecreasesConstantNot stableHintBoth are opposite to each other 87). Flemmings left-hand rule is mainly applicable to……?GeneratorMotorTransformerInductorHintThe function of this device is quite opposite to generator 88). The motor’s standard direction is?ClockwiseAnti clock wiseIn both directionsConstantHintIt is also called counter clockwise direction 89). If the field is opened in DC shunt motor, then?Motor speed will be maximumArmature current will be increasedMotor speed will be lowArmature current will be reducedHintThe dc shunt motor speed will be high 90). The characterization of DC machines can be done through…?ArmaturesBrushesCommutatorRotorHintThese are used in both motors and generators 91). All types of rotating machines are?AC machinesDC machinesHeat convertersElectromechanical convertersHintThe energy can be converted from electrical to mechanical 92). The structure of poles in?HorseshoeHetro polarCircleSquareHintIt has an alternating polarity 93). In a dc motor, the flow of current within a conductor is?ACDCTransientBothHintIt is alternating current 94). When a dc motor gets overheated?OverloadsNonstop workingLoose partsOpen armature coilHintWhen the motor gets too much load 95). The series field resistance as compared to shunt field is?LowHighInfiniteStableHintIt is quite opposite to the shunt field 96). When excessive motor vibration occurs?OverloadWhen a shaft is bentWorn bearingsThe armature coil is openHintIf we listen to a grating noise 97). Which type of dc motor is used to start heavy loads?Air motorSelf-excitedSeries motorShunt motorHintThis motor includes self-excited DC motors 98). When sparking occurs at the brushes?Due to dust on the commutatorLoose connectionsWorn bearingsHeavy loadsHintSparking occurs mainly because of the dirt on the commutator 99). The shunt motor speed is practical…?ConstantIncreasesDecreasesNo changeHintThe speed is stable practically Please refer to this link to know more about DC shunt motor 100). For punch presses, which motor is used?Cumulatively compoundedAir motorSeries motorDifferentially compoundedHintThese motors provide high starting torque Time is Up! Time's up
