11. 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%.
12. 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.
13. 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.
14. 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.
15. 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.
16. 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.
17. Capacitor start capacitor run single-phase Induction motor is used in ceiling fan.
A. True
B. False
Answer: A
Capacitor start capacitor run single-phase Induction motor is used in ceiling fan. The motor operation is silent and non-vibrational. It provides a high starting torque.
18. Which of the following are the types of Longitudinal stress?
A. Tensile stress, Compressive stress
B. Tensile stress, Volume stress
C. Tensile stress, Shear stress
D. Tensile stress, Lateral stress
Answer: A
Longitudinal stress is one type of stress. Longitudinal stress is of two types. It consists of Tensile stress and Compressive stress. It has a unit of N/m2.
19. Which type of motor is used for milling and grinding operations?
A. SCIM
B. WRIM
C. Split phase
D. Reluctance motor
Answer: A
The squirrel cage Induction motor is used for milling and grinding operations. SCIM has a rigid structure and high tolerating capability. It provides good running characteristics.
20. Calculate the work done in stretching the wire of length=2 m and the values of stress and strain are 16 N/m2 and 24.
