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 ? Rotor length Input power Back e.m.f. All of the above. Hint 2). In series, DC motor armature current is equal to? Back e.m.f Load current Voltage Speed Hint 3). Commutators are used in---? DC motors AC motors Both a and b. None of the above. Hint Please refer to this link to know more about Commutator 4). Which of the following is not a rotary part in the DC motor Rotor. Slip rings. Commutator. Field Winding. Hint 5). ---------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. Hint 6). The residual magnetism of DC machines is---? 14 to 19 percent 6 to 10 percent 2 to 3 percent 1 to 2 percent. Hint 7). In DC motors with the change in supply voltage, the starting Torque----- Increases Decreases Remains the same Equal to the supply voltage. Hint 8). In DC motors, the full load current decreases with ------ supply voltage. Increased Decreased. Constant value of None of the above Hint 9). When high torque and wide speed ranges are required---------is used. Induction motor. AC motor. DC motor All of the above. Hint 10). In DC motors Torque depends on -----? Armature current Back e.m.f. Speed Voltage. Hint 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. Decreases Zero Same as normal speed More than the normal speed. Hint 12). For high starting speed ------motor is used ? DC shunt motor Induction motor DC series motor. Both a and c. Hint 13. At high Torque speed, the DC series motor is ? Increases Decreases. Remains Constant Zero. Hint 14). Which of the following motor is used where an extensive range of control is required? AC Motor DC Motors Synchronous Motor Induction Motor Hint 15). In DC motor, the armature control voltage offers? Stable torque drive Stable current drive Stable voltage drive None of the above Hint 16). In machine tools, which of the following type of DC motor is used? Shunt motor Series motor Series wound Self-excited Hint 17). Which type of DC motor is used in elevators? Shunt motor DC cumulative compound motor Self-excited Series motor Hint 18). 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 Hint 19). The starting torque used by the load is…? Pumps Compressors Conveyors Blowers Hint 20). If the DC motor voltage supply is increased then….will be decreased? Full load current Starting torque Operating speed Efficiency Hint 21). 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 Hint 22). The resistance at the motor beginning is….? High Low Medium Very high Hint Please refer to this link to know more about Resistance 23). In which of the following, high starting torque is used? Air blower Locomotive Centrifugal pump Machines Hint 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. Hint 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 Hint DC Motor MCQs for Interviews 26). Who invented the first DC motor? William Marx William Sturgeon Thomas Davenport Antony Hint 27). How many types of DC motors? 2 3 4 5 Hint 28). Which type of DC motor has the utmost self-loading property? Self-excited Differentially compounded motor Series wound Shunt-wound Hint 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 Hint 30). The speed regulation of the series motor is? Fast Poor Medium Stable Hint 31). When the applied voltage of a DC motor is changed then the motor speed will be…? Not changed Changed Stable Slightly changed Hint 32). The torque breaking provided by the plugging is? Low High Medium Null Hint 33). The iron losses in the DC motor mainly occur within….? The armature The rotor The field The stator Hint 34). Which of the following part is available in DC motor? Stator Rotor Commutator Shaft Hint 35). Flemming's left-hand rules determine…? The direction of Motor’s rotation Motor working Motor stability Mechanical strength Hint 36). 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 Hint 37). In a DC motor, the induced EMF is…? Alternating Sinusoidal Square Triangle Hint 38). The armature resistance value within a DC motor is? 1 0.5 5 10 Hint 39). Which of the following is used to restrict the maximum torque in the DC motor? Speed Heating Commutation Armature current Hint 40). Which of the following is the main reason to affect the DC motor speed? Back emf Flux Armature current Load Hint 41). 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 Hint 42). The uni-directional torque can be generated through….? Only brushes Stator Rotor Both commutator & brushes Hint 43). Which motor is used in biomedical instruments? PMDC motor BLDC motor DC shunt motor DC series motor Hint 44). When the load is increased within a differential compound DC motor, the speed will be….? Stable Increased Decreased Motor will damage Hint 45). In an extremely unstable environment, which of the following motor is used? BLDC Series PMDC Air Motor Hint 46). A constant flux motor is also known as? DC shunt motor Air Motor Constant voltage motor Variable current motor Hint 47). In which of the following DC motor, dynamic braking is used? DC shunt motor Variable current motor Constant voltage motor Air Motor Hint 48). 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 Hint 49). In which of the following application, DC shunt motor is used…? Cranes Elevators Lathe Machines Electric Traction Hint 50). Which of the following device is used to change from AC to DC…? Windings Armature Split rings Bearings Hint DC Motor MCQs for Exams 51). 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 Hint 52). At which load, Hopkinson’s test is conducted on Motor? Overload Part load No-load Full load Hint 53). The shape of the brush within the DC motor is? Square Cylindrical Rectangular Triangle Hint 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 Hint 55). If the load is reduced in a DC shunt motor, then the speed will be….? Increased Reduced Stable None of the above Hint 56). 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 Hint 57). The max self-loading property of the motor is…? Air Motor Constant voltage motor DC shunt motor Differentially compound motor Hint 58). The material used to make commutators within a DC motor is? Copper Caste Iron Silver Silicon Steel Hint 59). The DC motor construction as compared to the DC generator is….? Same Different Same except frame construction Stable Hint 60). In which direction, Ward Leonard method provides variation in speed…? In one direction In two directions In three directions Under normal speed Hint 61). Which of the following motor is used to drive the rotating compressor? Synchronous Asynchronous DC series motor DC shunt motor Hint 62). 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 Hint 63). A 3 point starter is used in which type of DC motor? Series motor Compound motor Shunt motor Air motor Hint 64). The starter handle of the DC motor must be moved like? Quickly Slowly Smoothly With jerking Hint 65). 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 Hint 66). Which of the following is used as a motor controller? Relay Toggle switch Transformer Drum switch Hint 67). The armature copper loss in dc machine is also known as? Variable loss Windage loss Friction loss Iron loss Hint 68). Iron losses in dc machines mainly occur? Windings Armature core Yoke Brushes Hint 69). The essential component in the DC motor is? Rotor Stator Frame Commutator Hint 70). The order of the residual magnetism in DC motors is…? 1 to 2% 1 to 3% 2 to 3% 4 to 5% Hint 71). The self-relieving characteristic of the motor is…? Shunt motor Series motor Air motor Self-excited Hint 72). Once the DC motor armature turns then emf will be? Induced emf Back emf Mutually induced Self-induced Hint 73). 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 Hint 74). Retardation test is mainly used in which type of motors? DC series motor DC shunt motor Self-excited motor Air motor Hint 75). 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 Hint DC Motor MCQs for Quiz 76). The motor used in timers and signalling devices is…..? Air motor Reluctance motor Series motor Synchronous motor Hint 77). In refrigerators, which type of DC motor is used? Reluctance motor Series motor Air motor Synchronous motor Hint 78). In DC motor, the armature control voltage mainly provides…? Stable voltage drive Stable torque drive Stable current drive Changing voltage drive Hint 79). The main benefit of DC motor as compared to AC is? Stable Speed range is wide Not expensive Less weight Hint 80). What is the speed of a dc shunt motor when the load is increased? Slightly decreased Maximum decreased Increases Slightly increases Hint 81). If the voltage supply of dc motor is decreased then … will be increased? Full load current Load increased Starting torque Operating speed Hint 82). As compared to rated torque, the starting torque is used by the load is….? Conveyors Air compressors Blowers Pumps Hint 83). In a DC motor, the armature torque is high than the shaft torque because of……losses? Rotational Mechanical Back emf Copper Hint 84). 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 Hint 85). The principle of law used by DC motor is? Flemmings Law Lorentz Law Faradays Law Boltzman law Hint 86). If the flux within the field winding increases then the dc motor speed will be…? Increases Decreases Constant Not stable Hint 87). Flemmings left-hand rule is mainly applicable to……? Generator Motor Transformer Inductor Hint 88). The motor’s standard direction is? Clockwise Anti clock wise In both directions Constant Hint 89). 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 Hint 90). The characterization of DC machines can be done through…? Armatures Brushes Commutator Rotor Hint 91). All types of rotating machines are? AC machines DC machines Heat converters Electromechanical converters Hint 92). The structure of poles in? Horseshoe Hetro polar Circle Square Hint 93). In a dc motor, the flow of current within a conductor is? AC DC Transient Both Hint 94). When a dc motor gets overheated? Overloads Nonstop working Loose parts Open armature coil Hint 95). The series field resistance as compared to shunt field is? Low High Infinite Stable Hint 96). When excessive motor vibration occurs? Overload When a shaft is bent Worn bearings The armature coil is open Hint 97). Which type of dc motor is used to start heavy loads? Air motor Self-excited Series motor Shunt motor Hint 98). When sparking occurs at the brushes? Due to dust on the commutator Loose connections Worn bearings Heavy loads Hint 99). The shunt motor speed is practical…? Constant Increases Decreases No change Hint Please refer to this link to know more about DC shunt motor 100). For punch presses, which motor is used? Cumulatively compounded Air motor Series motor Differentially compounded Hint Time is Up! Time's up
