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