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 D.C. machines fractional pitch winding is used to improve cooling to increase the generated e.m.f. to reduce copper losses to reduce the sparking 2 / 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 3 / 25 Three point starter can be used for both shunt and compound motor shunt motor only compound motor only series motor only 4 / 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 remain unchanged increase four folds be doubled 5 / 25 Sparking is discouraged in a D.C. motor because it increases the input power con-sumption both and commutator gets damaged none of the above 6 / 25 A direct on line starter is used: for starting motors up to 20 H.P. up to 15 H.P. up to 10 H.P. up to 5 H.P. 7 / 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 8 / 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 9 / 25 If a D.C. motor is connected across the A.C. supply it will run at normal speed not run run at lower speed burn due to heat produced in the field winding by .eddy currents 10 / 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. 11 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will run noisy The motor will continue to run The motor will stop The armature may burn 12 / 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 13 / 25 Starters are used with D.C. motors because these motors have high starting torque back e.m.f. of these motors is zero initially these motors are not self-starting to restrict armature current as there is no back e.m.f. while starting 14 / 25 Sparking at the commutator of a D.C. motor may result in damage to commutator segments all of the above damage to commutator insulation increased power consumption 15 / 25 A three point starter is considered suitable for shunt compound and series motors shunt as well as compound motors all D.C. motors shunt motors 16 / 25 In a D.C. shunt motor speed is directly proportional to the armature current inversely proportional to the armature current independent of armature current proportional to the square of the current 17 / 25 can be obtained by increasing the field current decreasing the armature current increasing the armature current decreasing the field current 18 / 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 armature drop is negligible flux is proportional to armature current back e.m.f. is equal to armature drop 19 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Shunt motor Air motor Battery operated motor Series motor 20 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. series motor D.C. shunt motor Universal motor Synchronous motor 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 These days D.C. motors are widely used in air compressors electric traction pumping sets machine shops 23 / 25 The ratio of starting torque to full-load torque is least in case of series motors shunt motors none of the above compound motors 24 / 25 Usually wide and sensitive speed control is desired in case of centrifugal pumps elevators colliery winders steel rolling mills 25 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Voltage control method Field control method All above methods Armature control method कृपया सही सूचना भरें ताकि सर्टिफिकेट ईमेल पर भेजा जा सकें। NameEmailPhone NumberDistrictSchool/Coaching Name Your score is LinkedIn Facebook Twitter VKontakte 0% Restart quiz आपको यह क्विज अच्छी लगी तो 5 स्टार रेटिंग जरुर दें । Send feedback
