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 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because armature drop is negligible flux is proportional to armature current flux is practically constant in D:C. shunt motors back e.m.f. is equal to armature drop 2 / 25 can be obtained by decreasing the field current decreasing the armature current increasing the field current increasing the armature current 3 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will become zero decrease increase remain same 4 / 25 A direct on line starter is used: for starting motors up to 20 H.P. up to 5 H.P. up to 10 H.P. up to 15 H.P. 5 / 25 When two D.C. series motors are connected in parallel the resultant speed is zero loss than the normal speed normal speed more than the normal speed 6 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Shunt motor Air motor Series motor Battery operated motor 7 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Lenz’s law Fleming’s left-hand rule Faraday’s law Coloumb’s law 8 / 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 be doubled increase four folds reduce to one-fourth value 9 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? All above methods Field control method Armature control method Voltage control method 10 / 25 Usually wide and sensitive speed control is desired in case of steel rolling mills colliery winders centrifugal pumps elevators 11 / 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 armature may burn The motor will stop 12 / 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 13 / 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 14 / 25 Three point starter can be used for series motor only compound motor only shunt motor only both shunt and compound motor 15 / 25 A D.C. series motor is that which has almost constant speed can be started easily without load has its field winding consisting of thick wire and less turns has a poor torque 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 Starters are used with D.C. motors because these motors are not self-starting back e.m.f. of these motors is zero initially these motors have high starting torque to restrict armature current as there is no back e.m.f. while starting 18 / 25 In a D.C. shunt motor speed is directly proportional to the armature current inversely proportional to the armature current proportional to the square of the current independent of armature current 19 / 25 If a D.C. motor is connected across the A.C. supply it will run at normal speed not run burn due to heat produced in the field winding by .eddy currents run at lower speed 20 / 25 A three point starter is considered suitable for shunt motors all D.C. motors shunt as well as compound motors shunt compound and series motors 21 / 25 These days D.C. motors are widely used in electric traction air compressors pumping sets machine shops 22 / 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 23 / 25 In D.C. machines fractional pitch winding is used to reduce copper losses to improve cooling to increase the generated e.m.f. to reduce the sparking 24 / 25 Sparking is discouraged in a D.C. motor because both and it increases the input power con-sumption none of the above commutator gets damaged 25 / 25 Speed control by Ward Leonard method gives uniform speed variation in both directions above normal speed only. in one direction below normal speed only 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
