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