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