MCQ on DC motor 41-60

41. In D.C. shunt motors as load is reduced
(a) the speed will increase abruptly
(b) the speed will increase in proportion to reduction in load
(c) the speed will remain almost/constant✔
(d) the speed will reduce

42. A D.C. series motor is that which
(a) has its field winding consisting of thick wire and less turns✔
(b) has a poor torque
(c) can be started easily without load
(d) has almost constant speed

43. For starting a D.C. motor a starter is required because
(a) it limits the speed of the motor
(b) it limits the starting current to a safe value✔
(c) it starts the motor
(d) none of the above

44. The type of D.C. motor used for shears and punches is
(a) shunt motor
(b) series motor
(c) differential compoutid D.C. motor
(d) cumulative compound D.C. motor✔

45. If a D.C. motor is connected across the A.C. supply it will
(a) run at normal speed
(b) not run
(c) run at lower speed
(d) burn due to heat produced in the field winding by .eddy currents✔

46. To get the speed of D.C, motor below the normal without wastage of electrical energy is used.
(a) Ward Leonard control✔
(b) rheostatic control
(c) any of the above method
(d) none of the above method

47. When two D.C. series motors are connected in parallel, the resultant speed is
(a) more than the normal speed
(b) loss than the normal speed
(c) normal speed✔
(d) zero

48. The speed of a D.C. shunt motor more than its full-load speed can be obtained by
(a) decreasing the field current✔
(b) increasing the field current
(c) decreasing the armature current
(d) increasing the armature current

49. In a D.C. shunt motor, speed is
(a) independent of armature current✔
(b) directly proportional to the armature current
(c) proportional to the square of the current
(d) inversely proportional to the armature current

50. A direct on line starter is used: for starting motors
(a) up to 5 H.P.✔
(b) up to 10 H.P.
(c) up to 15 H.P.
(d) up to 20 H.P.

51. What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
(a) The motor will stop
(b) The motor will continue to run
(c) The armature may burn
(d) The motor will run noisy✔

52. In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
(a) back e.m.f. is equal to armature drop
(b) armature drop is negligible
(c) flux is proportional to armature current
(d) flux is practically constant in D:C. shunt motors✔

53. In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
(a) almost negligible
(b) rated full-load current
(c) less than full-load current
(d) more than full-load current✔

54. These days D.C. motors are widely used in
(a) pumping sets
(b) air compressors
(c) electric traction✔
(d) machine shops

55. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
(a) Frame
(b) Shaft
(c) Commutator✔
(d) Stator

56. In which of the following applications D.C. series motor is invariably tried?
(a) Starter for a car✔
(b) Drive for a water pump
(c) Fan motor
(d) Motor operation in A.C. or D.C.

57. In D.C. machines fractional pitch winding is used
(a) to improve cooling
(b) to reduce copper losses
(c) to increase the generated e.m.f.
(d) to reduce the sparking✔

58. A three point starter is considered suitable for
(a) shunt motors
(b) shunt as well as compound motors✔
(c) shunt, compound and series motors
(d) all D.C. motors

59. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
(a) 100%
(b) around 90%
(c) anywhere between 75% and 90%
(d) less than 50%✔

60. The ratio of starting torque to full-load torque is least in case of
(a) series motors
(b) shunt motors✔
(c) compound motors
(d) none of the above