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