Rating Of Motor MCQ [Free PDF] – Objective Question Answer for Rating Of Motor Quiz

41. Choose the correct relationship in Star connection with the positive sequence.

A. VL=Vp
B. VL=√3Vp
C. VL=√2Vp
D. IL=√3Ip

Answer: B

In the star connection line current is the same as the phase current. The line voltage is √3 times the phase voltage and leads by 30°.   

 

42. Calculate the 3-∅ power developed in the IM connected in star using the following data: Vp=7 V, IL=7 A, cosΦ=.6.

A. 88.5 W
B. 88.4 W
C. 88.8 W
D. 88.2 W

Answer: D

The power developed in the IM is √3VLILcos∅.

The power is independent of time and frequency.

In star connection, VL=√3Vp=12.12 V

P=√3VLILcos∅=3×20×5×.8=88.2 W.   

 

43. Hooke’s law is applicable within the elastic limit.

A. True
B. False

Answer: A

Hooke’s law is only applicable within the elastic limit. It states that within the elastic limit the strain is directly proportional to the stress.   

 

44. Calculate the load stress if the value of force is 20 N and the area of the cross-section is 2 m2.

A. 10 N/m2
B. 20 N/m2
C. 30 N/m2
D. 40 N/m2

Answer: A

The stress is defined as the ratio of the internal restoring force and the area of the cross-section.

Stress=Fres÷A=20÷2=10 N/m2.   

 

45. What is the effect of impurities on elasticity?

A. It will increase
B. Remains the same
C. It will decrease
D. It will slightly increase

Answer: D

The Young modulus of elasticity is slightly increased by the addition of impurities. The intermolecular forces inside the wire are effectively increased by impurity due to this external force can be easily opposed.   

 

46. Which of the following are the types of Stress?

A. Longitudinal stress, Volume stress, Tangential stress
B. Longitudinal stress, Volume stress
C. Longitudinal stress, Lateral stress, Tangential stress
D. Longitudinal stress, Shear stress

Answer: A

Three types of stress are Longitudinal stress, Volume stress, Tangential, or Shear stress. Stress is the ratio of restoring force and cross-section area.   

 

47. The relationship between Young’s modulus (Y), Bulk modulus (K) and Poisson’s ratio (μ) is _____________

A. Y=K(1-2μ)
B. Y=3K(1-2μ)
C. Y=5K(1-2μ)
D. Y=4K(1-8μ)

Answer: B

The relationship between Young’s modulus (Y), Bulk modulus (K), and Poisson’s ratio (μ) is Y=3K(1-2μ).

The Young modulus of elasticity is defined as the ratio of Longitudinal stress and Longitudinal strain.   

 

48. Calculate the work done in stretching the wire of volume=22 m3 and the values of stress and strain are 2 N/m2 and 4.

A. 66 J
B. 44 J
C. 22 J
D. 88 J

Answer: D

The work done in stretching a wire is .5 × Stress × Strain × Volume.

The value of the work done is

.5 × 22 × 4 × 2=88 J.   

 

49. Plasticity is the ability of the material to deform without breaking.

A. True
B. False

Answer: A

Plasticity is the ability of the material to deform without breaking. Plastic deformation occurs in metal forming processes.   

 

50. _________ motor operates at low power factor.

A. Capacitor run
B. Capacitor start
C. Shaded pole
D. Reluctance

Answer: C

Shaded pole motors operate at a low power factor. There is a weak magnetic field develops in the case of the Shaded pole motor. It is a single-phase AC Induction motor.   

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