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 method of speed control of D.C. machine will offer minimum efficiency ? Field control method Armature control method Voltage control method All above methods 2 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because armature drop is negligible back e.m.f. is equal to armature drop flux is practically constant in D:C. shunt motors flux is proportional to armature current 3 / 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 be doubled remain unchanged increase four folds 4 / 25 can be obtained by decreasing the field current increasing the field current increasing the armature current decreasing the armature current 5 / 25 In a D.C. shunt motor speed is inversely proportional to the armature current directly proportional to the armature current independent of armature current proportional to the square of the current 6 / 25 Speed control by Ward Leonard method gives uniform speed variation above normal speed only. in one direction in both directions below normal speed only 7 / 25 A three point starter is considered suitable for shunt compound and series motors all D.C. motors shunt motors shunt as well as compound motors 8 / 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 9 / 25 If a D.C. motor is connected across the A.C. supply it will not run run at lower speed run at normal speed burn due to heat produced in the field winding by .eddy currents 10 / 25 Sparking is discouraged in a D.C. motor because none of the above both and it increases the input power con-sumption commutator gets damaged 11 / 25 Starters are used with D.C. motors because 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 these motors are not self-starting 12 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Fleming’s left-hand rule Lenz’s law Coloumb’s law Faraday’s law 13 / 25 In D.C. machines fractional pitch winding is used to reduce the sparking to increase the generated e.m.f. to reduce copper losses to improve cooling 14 / 25 A D.C. series motor is that which has almost constant speed has its field winding consisting of thick wire and less turns can be started easily without load has a poor torque 15 / 25 Sparking at the commutator of a D.C. motor may result in all of the above damage to commutator insulation damage to commutator segments increased power consumption 16 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. series motor D.C. shunt motor Synchronous motor Universal motor 17 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Shunt motor Battery operated motor Air motor Series motor 18 / 25 Usually wide and sensitive speed control is desired in case of centrifugal pumps elevators colliery winders steel rolling mills 19 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will decrease increase remain same become zero 20 / 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 21 / 25 Three point starter can be used for series motor only both shunt and compound motor shunt motor only compound motor only 22 / 25 These days D.C. motors are widely used in electric traction pumping sets machine shops air compressors 23 / 25 The ratio of starting torque to full-load torque is least in case of series motors none of the above shunt motors compound motors 24 / 25 A direct on line starter is used: for starting motors up to 20 H.P. up to 5 H.P. up to 15 H.P. up to 10 H.P. 25 / 25 In which of the following applications D.C. series motor is invariably tried? Fan motor Drive for a water pump Motor operation in A.C. or D.C. Starter for a car 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
