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