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 A direct on line starter is used: for starting motors up to 15 H.P. up to 10 H.P. up to 20 H.P. up to 5 H.P. 2 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Air motor Series motor Battery operated motor Shunt motor 3 / 25 In D.C. machines fractional pitch winding is used to reduce copper losses to improve cooling to reduce the sparking to increase the generated e.m.f. 4 / 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 5 / 25 These days D.C. motors are widely used in air compressors pumping sets machine shops electric traction 6 / 25 Starters are used with D.C. motors because these motors are not self-starting these motors have high starting torque back e.m.f. of these motors is zero initially to restrict armature current as there is no back e.m.f. while starting 7 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will run noisy The armature may burn The motor will stop The motor will continue to run 8 / 25 Sparking is discouraged in a D.C. motor because both and commutator gets damaged none of the above it increases the input power con-sumption 9 / 25 When two D.C. series motors are connected in parallel the resultant speed is loss than the normal speed more than the normal speed normal speed zero 10 / 25 The ratio of starting torque to full-load torque is least in case of none of the above compound motors series motors shunt motors 11 / 25 In a D.C. shunt motor speed is independent of armature current inversely proportional to the armature current directly proportional to the armature current proportional to the square of the current 12 / 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 13 / 25 A three point starter is considered suitable for shunt motors shunt compound and series motors shunt as well as compound motors all D.C. motors 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 proportional to armature current back e.m.f. is equal to armature drop flux is practically constant in D:C. shunt motors 15 / 25 If a D.C. motor is connected across the A.C. supply it will run at lower speed run at normal speed not run burn due to heat produced in the field winding by .eddy currents 16 / 25 Three point starter can be used for shunt motor only compound motor only series motor only both shunt and compound motor 17 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Armature control method Voltage control method Field control method All above methods 18 / 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 19 / 25 Usually wide and sensitive speed control is desired in case of steel rolling mills colliery winders elevators centrifugal pumps 20 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will remain same decrease increase become zero 21 / 25 can be obtained by decreasing the armature current increasing the field current decreasing the field current increasing the armature current 22 / 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 a poor torque has almost constant speed 23 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Faraday’s law Coloumb’s law Lenz’s law Fleming’s left-hand rule 24 / 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 be doubled remain unchanged reduce to one-fourth value 25 / 25 Sparking at the commutator of a D.C. motor may result in damage to commutator insulation all of the above damage to commutator segments increased power consumption 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
