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