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