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