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