1. The ratio of the maximum fluctuation of energy to the ___________ is called coefficient of fluctuation of energy.
a) minimum fluctuation of energy
b) workdone per cycle
c) coefficient of fluctuation of energy
d) none of the mentioned
Explanation: Coefficient of fluctuation of energy is defined as the ratio of the maximum fluctuation of energy to the work done per cycle. It is usually denoted by CE.
2. Due to the centrifugal force acting on the rim, the flywheel arms will be subjected to
a) tensile stress
b) compressive stress
c) shear stress
d) none of the mentioned
Explanation: The following types of stresses are induced in the rim of a flywheel:
1. Tensile stress due to centrifugal force,
2. Tensile bending stress caused by the restraint of the arms, and
3. The shrinkage stresses due to unequal rate of cooling of casting. These stresses may be very high but there is no easy method of determining. This stress is taken care of by a factor of safety.
3. The tensile stress in the flywheel rim due to the centrifugal force acting on the rim is given by
a) ρ v2/4
b) ρ v2/2
c) 3ρ v2/4
d) ρ v2
Explanation: Tensile stress in the flywheel rim due to the centrifugal force = ρ v2
where ρ = Density of the flywheel material, and
v = Linear velocity of the flywheel.
4. The cross-section of the flywheel arms is usually
a) elliptical
b) rectangular
c) I-section
d) L-section
Explanation: The cross-section of the arms is usually elliptical with major axis as twice the minor axis, and it is designed for the maximum bending stress.
5. In order to find the maximum bending moment on the arms, it is assumed as a
a) simply supported beam carrying a uniformly distributed load over the arm
b) fixed at both ends (i.e. at the hub and at the free end of the rim) and carrying a uniformly distributed load over the arm.
c) cantilever beam fixed at the hub and carrying a concentrated load at the free end of the rim
d) none of the mentioned
Explanation: Due to the torque transmitted from the rim to the shaft or from the shaft to the rim, the arms will be subjected to bending, because they are required to carry the full torque load. In order to find out the maximum bending moment on the arms, it may be assumed as a centilever beam fixed at the hub and carrying a concentrated load at the free end of the rim.
6. The diameter of the hub of the flywheel is usually taken
a) equal to the diameter of the shaft
b) twice the diameter of the shaft
c) three times the diameter of the shaft
d) four times the diameter of the shaft
Explanation: The diameter of hub is usually taken as twice the diameter of shaft and length from 2 to 2.5 times the shaft diameter. It is generally taken equal to width of the rim.
7. In a four stroke I.C. engine, the turning moment during the compression stroke is
a) positive throughout
b) negative throughout
c) positive during major portion of the stroke
d) negative during major portion of the stroke
Explanation: Since the pressure inside the engine cylinder is less than the atmospheric pressure during the suction stroke, therefore a negative loop is formed. During the compression stroke, the work is done on the gases, therefore a higher negative loop is obtained.
8. The maximum fluctuation of energy is the.
a) difference between the maximum and minimum energies
b) sum of the maximum and minimum energies
c) variations of energy above and below the mean resisting torque to the
d) ratio of the mean resisting torque to the workdone per cycle
Explanation: The difference between the maximum and the minimum energies is known as maximum fluctuation of energy.
9. The co-efficient of fluctuation of energy is the ratio of maximum energy to the minimum energy.
a) True
b) False
Explanation: The co-efficient of fluctuation of energy is the ratio of the maximum fluctuation of energy to the work done per cycle.
10. Which of the following statement is wrong?
a) The difference between the maximum and minimum energies is called maximum fluctuation of energy.
b) The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed.
c) The variations of energy above and below the mean resisting torque line is known as fluctuation of energy.
d) None of the mentioned
Explanation: All the statements are correct.
The difference between the maximum and minimum energies is called maximum fluctuation of energy.
The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed.
The variations of energy above and below the mean resisting torque line is known as fluctuation of energy.