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 Speed control by Ward Leonard method gives uniform speed variation in both directions in one direction below normal speed only above normal speed only. 2 / 25 In D.C. machines fractional pitch winding is used to increase the generated e.m.f. to reduce copper losses to improve cooling to reduce the sparking 3 / 25 When two D.C. series motors are connected in parallel the resultant speed is loss than the normal speed normal speed zero more than the normal speed 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 remain unchanged reduce to one-fourth value increase four folds be doubled 5 / 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 6 / 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 are not self-starting these motors have high starting torque back e.m.f. of these motors is zero initially 7 / 25 In a D.C. shunt motor speed is directly proportional to the armature current proportional to the square of the current independent of armature current inversely proportional to the armature current 8 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will continue to run The armature may burn The motor will stop The motor will run noisy 9 / 25 Usually wide and sensitive speed control is desired in case of centrifugal pumps steel rolling mills colliery winders elevators 10 / 25 The ratio of starting torque to full-load torque is least in case of none of the above shunt motors compound motors series motors 11 / 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 12 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Battery operated motor Air motor Shunt motor Series motor 13 / 25 These days D.C. motors are widely used in electric traction air compressors pumping sets machine shops 14 / 25 If a D.C. motor is connected across the A.C. supply it will run at normal speed not run burn due to heat produced in the field winding by .eddy currents run at lower speed 15 / 25 A three point starter is considered suitable for shunt compound and series motors shunt as well as compound motors shunt motors all D.C. motors 16 / 25 A D.C. series motor is that which has a poor torque has its field winding consisting of thick wire and less turns can be started easily without load has almost constant speed 17 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will become zero remain same increase decrease 18 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Coloumb’s law Lenz’s law Fleming’s left-hand rule Faraday’s law 19 / 25 Three point starter can be used for both shunt and compound motor shunt motor only compound motor only series motor only 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 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 22 / 25 In which of the following applications D.C. series motor is invariably tried? Starter for a car Motor operation in A.C. or D.C. Fan motor Drive for a water pump 23 / 25 A direct on line starter is used: for starting motors up to 10 H.P. up to 15 H.P. up to 5 H.P. up to 20 H.P. 24 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. series motor D.C. shunt motor Synchronous motor Universal motor 25 / 25 can be obtained by decreasing the field current increasing the field current decreasing the armature current increasing the armature current 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
