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 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 2 / 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 3 / 25 Three point starter can be used for compound motor only shunt motor only both shunt and compound motor series motor only 4 / 25 These days D.C. motors are widely used in electric traction air compressors pumping sets machine shops 5 / 25 A direct on line starter is used: for starting motors up to 10 H.P. up to 20 H.P. up to 5 H.P. up to 15 H.P. 6 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Armature control method All above methods Voltage control method Field control method 7 / 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 8 / 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 back e.m.f. is equal to armature drop flux is proportional to armature current armature drop is negligible 9 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will run noisy The motor will stop The armature may burn The motor will continue to run 10 / 25 Usually wide and sensitive speed control is desired in case of steel rolling mills centrifugal pumps colliery winders elevators 11 / 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 lower speed run at normal speed 12 / 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 are not self-starting these motors have high starting torque back e.m.f. of these motors is zero initially 13 / 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 14 / 25 Speed control by Ward Leonard method gives uniform speed variation below normal speed only in one direction above normal speed only. in both directions 15 / 25 can be obtained by increasing the field current decreasing the field current increasing the armature current decreasing the armature current 16 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Battery operated motor Air motor Shunt motor Series motor 17 / 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 remain unchanged be doubled increase four folds reduce to one-fourth value 18 / 25 In a D.C. shunt motor speed is inversely proportional to the armature current proportional to the square of the current independent of armature current directly proportional to the armature current 19 / 25 Sparking is discouraged in a D.C. motor because none of the above commutator gets damaged both and it increases the input power con-sumption 20 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will decrease remain same become zero increase 21 / 25 A three point starter is considered suitable for all D.C. motors shunt compound and series motors shunt motors shunt as well as compound motors 22 / 25 The ratio of starting torque to full-load torque is least in case of series motors compound motors shunt motors none of the above 23 / 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 24 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Coloumb’s law Fleming’s left-hand rule Faraday’s law Lenz’s law 25 / 25 Which of the following motors one will choose to drive the rotary compressor ? Universal motor D.C. series motor D.C. shunt motor Synchronous motor 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
