21. Which one of the following is the correct relationship?
A. F=μR
B. F=4μR
C. F=3μR
D. F=2μR
Answer: A
The value of the friction force is the product of the coefficient of friction and normal reaction. The correct value is F=μR.
22. Calculate the velocity of the bottom point of the wheel for perfect rolling using the data: r=20 cm, ω=100 rad/sec.
A. 20 m/sec
B. 40 m/sec
C. 60 m/sec
D. 80 m/sec
Answer: A
The velocity of the bottom point of the wheel for perfect rolling is the product of the radius and angular velocity. It is expressed in terms of m/sec.
V = r×ω = .2×100=20 m/sec.
23. The coefficient of adhesion is maximum when rails are dusty.
A. True
B. False
Answer: B
The coefficient of adhesion is maximum when rails are dry. The coefficient of adhesion depends on the nature of the material.
24. Calculate the value of the coefficient of adhesion for dusty rails if the value of the coefficient of adhesion for dry rails is .55.
A. 0.65
B. 0.89
C. 0.97
D. 0.48
Answer: D
The value of the coefficient of adhesion for dusty rails is .48. The value of the coefficient of adhesion for dry rails is maximum.
25. Calculate the value measured by Moving Iron when a sinusoidal voltage signal V(t) = √2sin(3ωt) is applied to it.
A. 2 V
B. 1 V
C. 3 V
D. 4 V
Answer: B
Moving iron instrument measures the r.m.s value of the input signal. The r.m.s value of the sinusoidal signal is
√2÷√2 = 1 V.
26. The value of area under a velocity-time graph is _________
A. Acceleration
B. Displacement
C. Force
D. Momentum
Answer: B
The value of the area under a velocity-time graph is displacement. The velocity is the ratio of displacement and time.
27. The value of area under acceleration-time graph is _________
A. Velocity
B. Displacement
C. Force
D. Impulse
Answer: A
The value of the area under an acceleration-time graph is velocity. The acceleration is the ratio of velocity and time.
28. The value of area under force-time graph is _________
A. Reaction
B. Change in momentum
C. Force
D. Torque
Answer: B
The value of the area under a force-time graph is a change in momentum. The force is the ratio of change in momentum with respect to time.
29. Full form of HVDC is _________
A. High Voltage Direct Current
B. High Voltage Distribution Combination
C. High-Value Direct Current
D. High-Value Distribution Combination
Answer: A
The full form of HVDC is High voltage direct current. HVDC is more preferred than HVAC because of minimum losses.
30. Full form of HVAC is _________
A. High Voltage Alternative Current
B. High Voltage Alternating Current
C. High-Value Alternating Combination
D. High-Value Alternative Counter
Answer: B
The full form of HVAC is a High voltage alternating current. It is mostly preferred for smaller distances. HVAC has higher losses than HVDC.
