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 can be obtained by increasing the armature current decreasing the armature current decreasing the field current increasing the field current 2 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Series motor Air motor Battery operated motor Shunt motor 3 / 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 4 / 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 5 / 25 Sparking is discouraged in a D.C. motor because none of the above commutator gets damaged it increases the input power con-sumption both and 6 / 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 7 / 25 A direct on line starter is used: for starting motors up to 15 H.P. up to 10 H.P. up to 20 H.P. up to 5 H.P. 8 / 25 Three point starter can be used for compound motor only shunt motor only both shunt and compound motor series motor only 9 / 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 10 / 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 11 / 25 In which of the following applications D.C. series motor is invariably tried? Fan motor Drive for a water pump Starter for a car Motor operation in A.C. or D.C. 12 / 25 Speed control by Ward Leonard method gives uniform speed variation in both directions above normal speed only. below normal speed only in one direction 13 / 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 14 / 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 15 / 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 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 increase four folds be doubled remain unchanged reduce to one-fourth value 17 / 25 Sparking at the commutator of a D.C. motor may result in all of the above damage to commutator insulation increased power consumption 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 increase become zero remain same decrease 19 / 25 These days D.C. motors are widely used in machine shops air compressors electric traction pumping sets 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 Usually wide and sensitive speed control is desired in case of centrifugal pumps steel rolling mills colliery winders elevators 22 / 25 A D.C. series motor is that which has its field winding consisting of thick wire and less turns can be started easily without load has almost constant speed has a poor torque 23 / 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 24 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is proportional to armature current flux is practically constant in D:C. shunt motors armature drop is negligible back e.m.f. is equal to armature drop 25 / 25 In D.C. machines fractional pitch winding is used to improve cooling to reduce copper losses to increase the generated e.m.f. to reduce the sparking 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
