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 Starters are used with D.C. motors because back e.m.f. of these motors is zero initially these motors have high starting torque these motors are not self-starting to restrict armature current as there is no back e.m.f. while starting 2 / 25 Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? Fleming’s left-hand rule Lenz’s law Faraday’s law Coloumb’s law 3 / 25 What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? The motor will stop The armature may burn The motor will run noisy The motor will continue to run 4 / 25 If the speed of a D.C. shunt motor is increased the back e.m.f. of the motor will decrease become zero increase remain same 5 / 25 A three point starter is considered suitable for shunt as well as compound motors shunt motors shunt compound and series motors all D.C. motors 6 / 25 can be obtained by increasing the armature current decreasing the field current increasing the field current decreasing the armature current 7 / 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 armature drop is negligible back e.m.f. is equal to armature drop 8 / 25 In which of the following applications D.C. series motor is invariably tried? Starter for a car Motor operation in A.C. or D.C. Fan motor Drive for a water pump 9 / 25 Sparking is discouraged in a D.C. motor because it increases the input power con-sumption both and commutator gets damaged none of the above 10 / 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 11 / 25 In D.C. machines fractional pitch winding is used to improve cooling to reduce copper losses to increase the generated e.m.f. to reduce the sparking 12 / 25 A direct on line starter is used: for starting motors up to 10 H.P. up to 15 H.P. up to 5 H.P. up to 20 H.P. 13 / 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 14 / 25 In a D.C. shunt motor speed is directly proportional to the armature current inversely proportional to the armature current independent of armature current proportional to the square of the current 15 / 25 Which of the following method of speed control of D.C. machine will offer minimum efficiency ? Armature control method Voltage control method Field control method All above methods 16 / 25 Three point starter can be used for compound motor only both shunt and compound motor shunt motor only series motor only 17 / 25 Sparking at the commutator of a D.C. motor may result in increased power consumption all of the above damage to commutator segments damage to commutator insulation 18 / 25 These days D.C. motors are widely used in air compressors machine shops electric traction pumping sets 19 / 25 Speed control by Ward Leonard method gives uniform speed variation below normal speed only in both directions above normal speed only. in one direction 20 / 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 reduce to one-fourth value remain unchanged be doubled 21 / 25 Usually wide and sensitive speed control is desired in case of elevators centrifugal pumps colliery winders steel rolling mills 22 / 25 Which of the following motors one will choose to drive the rotary compressor ? Synchronous motor D.C. series motor D.C. shunt motor Universal motor 23 / 25 A D.C. series motor is that which has almost constant speed has a poor torque can be started easily without load has its field winding consisting of thick wire and less turns 24 / 25 Which of the following motor is preferred for operation in highly explosive atmosphere ? Series motor Battery operated motor Air motor Shunt motor 25 / 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 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
