By Surendra | June 10, 2020 0 Comment 0% 1 Created by Surendra DC Motors Quiz in English Set 1 All Important Question Answers for Electrician Related Exams 1 / 25 These days D.C. motors are widely used in air compressors electric traction machine shops pumping sets 2 / 25 Three point starter can be used for compound motor only both shunt and compound motor shunt motor only series motor only 3 / 25 In D.C. machines fractional pitch winding is used to improve cooling to reduce copper losses to increase the generated e.m.f. to reduce the sparking 4 / 25 In case the back e.m.f. and the speed of a D.C. motor are doubled the torque developed by the motor will remain unchanged increase four folds reduce to one-fourth value be doubled 5 / 25 Sparking is discouraged in a D.C. motor because none of the above both and it increases the input power con-sumption commutator gets damaged 6 / 25 A three point starter is considered suitable for shunt motors shunt as well as compound motors all D.C. motors shunt compound and series motors 7 / 25 Sparking at the commutator of a D.C. motor may result in increased power consumption damage to commutator segments all of the above damage to commutator insulation 8 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Shunt motor Series motor Air motor Battery operated motor 9 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Fleming’s left-hand rule Lenz’s law Faraday’s law Coloumb’s law 10 / 25 The ratio of starting torque to full-load torque is least in case of compound motors series motors shunt motors none of the above 11 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because back e.m.f. is equal to armature drop flux is practically constant in D:C. shunt motors armature drop is negligible flux is proportional to armature current 12 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will continue to run The motor will run noisy The motor will stop The armature may burn 13 / 25 In which of the following applications D.C. series motor is invariably tried? Drive for a water pump Motor operation in A.C. or D.C. Starter for a car Fan motor 14 / 25 If a D.C. motor is connected across the A.C. supply it will burn due to heat produced in the field winding by .eddy currents run at normal speed run at lower speed not run 15 / 25 When two D.C. series motors are connected in parallel the resultant speed is normal speed loss than the normal speed zero more than the normal speed 16 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will remain same decrease increase become zero 17 / 25 Usually wide and sensitive speed control is desired in case of elevators colliery winders steel rolling mills centrifugal pumps 18 / 25 In a D.C. shunt motor speed is independent of armature current inversely proportional to the armature current directly proportional to the armature current proportional to the square of the current 19 / 25 A D.C. series motor is that which has almost constant speed has its field winding consisting of thick wire and less turns can be started easily without load has a poor torque 20 / 25 Starters are used with D.C. motors because back e.m.f. of these motors is zero initially to restrict armature current as there is no back e.m.f. while starting these motors have high starting torque these motors are not self-starting 21 / 25 Which of the following motors one will choose to drive the rotary compressor ? Universal motor D.C. series motor D.C. shunt motor Synchronous motor 22 / 25 Speed control by Ward Leonard method gives uniform speed variation below normal speed only above normal speed only. in one direction in both directions 23 / 25 A direct on line starter is used: for starting motors up to 15 H.P. up to 5 H.P. up to 10 H.P. up to 20 H.P. 24 / 25 can be obtained by decreasing the field current increasing the field current increasing the armature current decreasing the armature current 25 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Voltage control method Armature control method All above methods Field control method कृपया सही सूचना भरें ताकि सर्टिफिकेट ईमेल पर भेजा जा सकें। Your score is LinkedIn Facebook Twitter 0% Restart quiz आपको यह क्विज अच्छी लगी तो 5 स्टार रेटिंग जरुर दें । Send feedback
