By Surendra | June 10, 2020 0 Comment 0% 1 Created by Surendra DC Motors Quiz in English Set 1 All Important Question Answers for Electrician Related Exams 1 / 25 Starters are used with D.C. motors because back e.m.f. of these motors is zero initially to restrict armature current as there is no back e.m.f. while starting these motors are not self-starting these motors have high starting torque 2 / 25 Three point starter can be used for both shunt and compound motor series motor only compound motor only shunt motor only 3 / 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. 4 / 25 A D.C. series motor is that which has almost constant speed has its field winding consisting of thick wire and less turns has a poor torque can be started easily without load 5 / 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 6 / 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 7 / 25 Usually wide and sensitive speed control is desired in case of steel rolling mills centrifugal pumps elevators colliery winders 8 / 25 can be obtained by increasing the field current increasing the armature current decreasing the armature current decreasing the field current 9 / 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 10 / 25 A three point starter is considered suitable for shunt motors shunt compound and series motors shunt as well as compound motors all D.C. motors 11 / 25 The ratio of starting torque to full-load torque is least in case of none of the above compound motors shunt motors series motors 12 / 25 If a D.C. motor is connected across the A.C. supply it will not run burn due to heat produced in the field winding by .eddy currents run at lower speed run at normal speed 13 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Armature control method Field control method All above methods Voltage control method 14 / 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 practically constant in D:C. shunt motors flux is proportional to armature current 15 / 25 Which of the following motors one will choose to drive the rotary compressor ? Universal motor D.C. series motor D.C. shunt motor Synchronous motor 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 reduce to one-fourth value remain unchanged be doubled increase four folds 17 / 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 stop The motor will run noisy 18 / 25 These days D.C. motors are widely used in electric traction pumping sets air compressors machine shops 19 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Battery operated motor Air motor Shunt motor Series motor 20 / 25 Speed control by Ward Leonard method gives uniform speed variation in both directions below normal speed only in one direction above normal speed only. 21 / 25 When two D.C. series motors are connected in parallel the resultant speed is normal speed zero more than the normal speed loss than the normal speed 22 / 25 In D.C. machines fractional pitch winding is used to reduce the sparking to increase the generated e.m.f. to improve cooling to reduce copper losses 23 / 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. 24 / 25 Sparking at the commutator of a D.C. motor may result in damage to commutator segments increased power consumption damage to commutator insulation all of the above 25 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Faraday’s law Fleming’s left-hand rule Coloumb’s law Lenz’s law 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
