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