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 If a D.C. motor is connected across the A.C. supply it will not run run at lower speed burn due to heat produced in the field winding by .eddy currents run at normal speed 2 / 25 Sparking is discouraged in a D.C. motor because both and commutator gets damaged it increases the input power con-sumption none of the above 3 / 25 In which of the following applications D.C. series motor is invariably tried? Motor operation in A.C. or D.C. Drive for a water pump Fan motor Starter for a car 4 / 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 Coloumb’s law Faraday’s law 5 / 25 can be obtained by decreasing the field current increasing the armature current decreasing the armature current increasing the field current 6 / 25 A D.C. series motor is that which has its field winding consisting of thick wire and less turns can be started easily without load has almost constant speed has a poor torque 7 / 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 reduce to one-fourth value be doubled remain unchanged 8 / 25 The ratio of starting torque to full-load torque is least in case of series motors none of the above shunt motors compound motors 9 / 25 Usually wide and sensitive speed control is desired in case of centrifugal pumps colliery winders steel rolling mills elevators 10 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will continue to run The motor will stop The motor will run noisy The armature may burn 11 / 25 In a D.C. shunt motor speed is inversely proportional to the armature current independent of armature current proportional to the square of the current directly proportional to the armature current 12 / 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 13 / 25 A direct on line starter is used: for starting motors up to 10 H.P. up to 5 H.P. up to 20 H.P. up to 15 H.P. 14 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because armature drop is negligible flux is practically constant in D:C. shunt motors flux is proportional to armature current back e.m.f. is equal to armature drop 15 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Voltage control method All above methods Field control method Armature control method 16 / 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 17 / 25 Starters are used with D.C. motors because these motors have high starting torque to restrict armature current as there is no back e.m.f. while starting back e.m.f. of these motors is zero initially these motors are not self-starting 18 / 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. 19 / 25 Three point starter can be used for both shunt and compound motor series motor only compound motor only shunt motor only 20 / 25 When two D.C. series motors are connected in parallel the resultant speed is more than the normal speed loss than the normal speed normal speed zero 21 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. shunt motor Universal motor D.C. series motor Synchronous motor 22 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will decrease become zero remain same increase 23 / 25 In D.C. machines fractional pitch winding is used to reduce the sparking to improve cooling to increase the generated e.m.f. to reduce copper losses 24 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Air motor Series motor Shunt motor Battery operated motor 25 / 25 These days D.C. motors are widely used in machine shops air compressors electric traction pumping sets कृपया सही सूचना भरें ताकि सर्टिफिकेट ईमेल पर भेजा जा सकें। Your score is LinkedIn Facebook Twitter 0% Restart quiz आपको यह क्विज अच्छी लगी तो 5 स्टार रेटिंग जरुर दें । Send feedback
