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 Battery operated motor Series motor 2 / 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. Starter for a car Fan motor 3 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will run noisy The armature may burn The motor will continue to run The motor will stop 4 / 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 5 / 25 In D.C. machines fractional pitch winding is used to increase the generated e.m.f. to reduce the sparking to reduce copper losses to improve cooling 6 / 25 The ratio of starting torque to full-load torque is least in case of shunt motors compound motors series motors none of the above 7 / 25 A D.C. series motor is that which has almost constant speed has a poor torque can be started easily without load has its field winding consisting of thick wire and less turns 8 / 25 A three point starter is considered suitable for all D.C. motors shunt motors shunt as well as compound motors shunt compound and series motors 9 / 25 Sparking is discouraged in a D.C. motor because it increases the input power con-sumption none of the above both and commutator gets damaged 10 / 25 Starters are used with D.C. motors because to restrict armature current as there is no back e.m.f. while starting these motors have high starting torque these motors are not self-starting back e.m.f. of these motors is zero initially 11 / 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 12 / 25 A direct on line starter is used: for starting motors up to 10 H.P. up to 15 H.P. up to 20 H.P. up to 5 H.P. 13 / 25 can be obtained by decreasing the armature current increasing the field current decreasing the field current increasing the armature current 14 / 25 When two D.C. series motors are connected in parallel the resultant speed is zero normal speed loss than the normal speed more than the normal speed 15 / 25 Usually wide and sensitive speed control is desired in case of elevators centrifugal pumps steel rolling mills colliery winders 16 / 25 In a D.C. shunt motor speed is proportional to the square of the current independent of armature current inversely proportional to the armature current directly proportional to the armature current 17 / 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 18 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will remain same decrease increase become zero 19 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. series motor Synchronous motor D.C. shunt motor Universal motor 20 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? All above methods Voltage control method Field control method Armature control method 21 / 25 Three point starter can be used for compound motor only both shunt and compound motor series motor only shunt motor only 22 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors back e.m.f. is equal to armature drop flux is proportional to armature current armature drop is negligible 23 / 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 24 / 25 Speed control by Ward Leonard method gives uniform speed variation below normal speed only in one direction above normal speed only. in both directions 25 / 25 These days D.C. motors are widely used in electric traction air compressors pumping sets machine shops 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
