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