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