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