Objective Questions on Single Phase Motors

46. The short coming of repulsion motor is

(A) variation of speed with load
(B) low power factor
(C) tendency to spark at brushes
(D) all of the above.

47. The disadvantage of shaded pole motor is

(A) low starting torque’
(B) low efficiency
(C) very little over load capacity
(D) all of the above.

48. The efficiency of shaded pole motor is in the range

(A) 80 to 95 percent
(B) 70 to 80 percent
(C) 50 to 70 percent
(D) 5 to 35 percent.

49. For domestic sewing machine the size of the motor required will be

(A) 10-15 watts
(B) 15-25 watts
(C) 100-150 watts
(D) 250 to 750 watts.

50. A ceiling fan of 1400 mm sweep will have motor rating of

(A) 10 to 15 watts
(B) 50 to 70 watts
(C) 120 to 180 watts
(D) 250 to 500 watts.

51. Which of the following applications would need the smallest size of motor ?

(A) Domestic motor
(B) Electric clock
(C) Table fan
(D) Sewing machine.

52. All single phase ac motors are designed to operate usually on

(A) 220 V only
(B)220V + 10V
(C) 220 ± 0 V
(D) 220 ± 10% volts.

53. All single phase ac motors are designed usually to operate on the frequency

(A) 50 Hz
(B) 50 ± 0.5 Hz
(C) 50 ±1 Hz
(D) 50. ± 5 Hz.

54. When a dc series motor is connected to ac supply, it will

(A) spark excessively
(B) give poor efficiency
(C) run on poor power factor
(D) all of the above.

55. The torque-speed characteristic of a repulsion motor resembles that of which of the following dc motor ?

(A) separately excited motor
(B) shunt motor
(C) series is motor
(D) compound motor.

56. In a single phase capacitor motor the direction of rotation will be in the opposite direction to the original when

(A) electrolytic capacitor is replaced by paper capacitor
(B) two capacitors of equal value are used
(C) capacitor is replaced by a resistance
(D) capacitor is replaced by an inductor.

57. In a hysteresis motor, the position of shaded pole with respect to main pole determines

(A) speed of motor
(B) direction of rotation
(C) hysteresis loss
(D) no load rpm.

58. In a shaded pole motor, the direction of rotation is from

(A) main pole to shaded pole
(B) shaded pole to main pole
(C) depends on supply line polarity.

59. Which motor is generally used in tape recorders ?

(A) Universal motor
(B) Reluctance motor
(C) Split phase motor
(D) Hysteresis motor.

60. In a shaded pole motor, shading coils are used to

(A) reduce windage losses
(B) reduce friction losses
(C) produce rotating magnetic field
(D) to protect against sparking.