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 which of the following applications D.C. series motor is invariably tried? Drive for a water pump Fan motor Starter for a car Motor operation in A.C. or D.C. 2 / 25 Usually wide and sensitive speed control is desired in case of elevators steel rolling mills colliery winders centrifugal pumps 3 / 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 Lenz’s law Faraday’s law 4 / 25 If a D.C. motor is connected across the A.C. supply it will run at normal speed burn due to heat produced in the field winding by .eddy currents run at lower speed not run 5 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? All above methods Armature control method Voltage control method Field control method 6 / 25 Three point starter can be used for both shunt and compound motor compound motor only series motor only shunt motor only 7 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will stop The armature may burn The motor will continue to run The motor will run noisy 8 / 25 In case of D.C. shunt motors the speed is dependent on back e.m.f. only because armature drop is negligible back e.m.f. is equal to armature drop flux is practically constant in D:C. shunt motors flux is proportional to armature current 9 / 25 When two D.C. series motors are connected in parallel the resultant speed is zero loss than the normal speed more than the normal speed normal speed 10 / 25 Sparking at the commutator of a D.C. motor may result in all of the above damage to commutator segments increased power consumption damage to commutator insulation 11 / 25 These days D.C. motors are widely used in electric traction air compressors machine shops pumping sets 12 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Air motor Shunt motor Series motor Battery operated motor 13 / 25 A three point starter is considered suitable for all D.C. motors shunt as well as compound motors shunt compound and series motors shunt motors 14 / 25 Starters are used with D.C. motors because 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 these motors have high starting torque 15 / 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 remain unchanged increase four folds reduce to one-fourth value 16 / 25 Which of the following motors one will choose to drive the rotary compressor ? D.C. shunt motor Synchronous motor D.C. series motor Universal motor 17 / 25 A direct on line starter is used: for starting motors up to 5 H.P. up to 10 H.P. up to 15 H.P. up to 20 H.P. 18 / 25 In a D.C. shunt motor speed is inversely proportional to the armature current proportional to the square of the current directly proportional to the armature current independent of armature current 19 / 25 Speed control by Ward Leonard method gives uniform speed variation in one direction above normal speed only. in both directions below normal speed only 20 / 25 In D.C. machines fractional pitch winding is used to increase the generated e.m.f. to reduce the sparking to reduce copper losses to improve cooling 21 / 25 A D.C. series motor is that which has a poor torque can be started easily without load has almost constant speed has its field winding consisting of thick wire and less turns 22 / 25 The ratio of starting torque to full-load torque is least in case of shunt motors none of the above series motors compound motors 23 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will increase remain same decrease become zero 24 / 25 can be obtained by decreasing the field current increasing the field current increasing the armature current decreasing the armature current 25 / 25 Sparking is discouraged in a D.C. motor because none of the above both and it increases the input power con-sumption commutator gets damaged 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
