21. 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.
22. _________ 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.
23. Calculate the compensator rating required for cos(Φ)=.7.
A. 0.71 P.U
B. 0.21 P.U
C. 0.47 P.U
D. 0.12 P.U
Answer: A
The compensator rating can be calculated using the relation
QP.U=√1-cos2(∅)
=√1-.49=.71.
This per unit value VAR compensator is required to improve the power factor of the system.
24. Full form of SPWM.
A. Sinusoidal pulse width modulation
B. State per width modulation
C. State pulse width modulation
D. Sinusoidal per width modulation
Answer: A
SPWM stands for sinusoidal pulse width modulation. SPWM is a high-frequency PWM technique. This technique is used to achieve variable voltage levels.
25. Which harmonic is not present in 3-Φ fully controlled rectifier?
A. 3rd harmonic
B. 5th harmonic
C. 7th harmonic
D. 11th harmonic
Answer: A
Triple harmonics are absent in the case of a 3-phase fully controlled rectifier. Because of the absence of triple harmonics, the THD of the rectifier is 31%.
26. Lowest order harmonics present in 3-Φ fully controlled rectifier is __________
A. 5th
B. 7th
C. 3rd
D. 2nd
Answer: A
Only 6k±1 order harmonics are present in 3-Φ fully controlled rectifiers. The lowest order harmonic is the 5th harmonic for k=1. Third-order harmonics are absent in 3-Φ fully controlled rectifier.
27. Calculate the moment of inertia of the circular hollow disk having a mass of 2 kg and an internal radius of 5 m and an external radius of 10 m.
A. 125 kgm2
B. 127 kgm2
C. 122 kgm2
D. 123 kgm2
Answer: A
The moment of inertia of the circular hollow disk can be calculated using the formula
I=M(R12+R22)÷2.
The mass of the circular hollow disk and radius is given
I=(1)×{(5)2+(10)2}=125 kgm2.
It depends upon the orientation of the rotational axis.
28. Calculate the mass of the solid cylinder having a mass of 4 kgm2 and radius of 4 m & length of 12 m.
A. 64 kgm2
B. 68 kgm2
C. 67 kgm2
D. 69 kgm2
Answer: A
The moment of inertia of the solid cylinder can be calculated using the formula
I= M(l2÷12+R22÷4).
The mass of the solid cylinder and radius and the length are given.
I=(4){(16)}= 64 kgm2.
It depends upon the orientation of the rotational axis.
29. Calculate the moment of inertia of the flywheel of mass of 45 kg and radius of 2 m.
A. 185 kg-m2
B. 180 kg-m2
C. 175 kg-m2
D. 170 kg-m2
Answer: B
The moment of inertia of the flywheel can be calculated using the formula I=M(R2).
The mass of the flywheel and radius is given
I=(45)×(2)2=180 kg-m2.
It depends upon the orientation of the rotational axis.
30. Electric motor and control system are the basic elements of the electric drive.
A. True
B. False
Answer: A
The electric motor and control system are the basic elements of the electric drive. The electric drive uses the control system methods to control the speed and torque of the motor.
