1. Two pulleys are connected by a belt. The sum of the diameter of two pulleys is 90 cm and while one makes 50 rpm, the other makes 20 rpm. What will be the diameters of the other pulley?
a) 14.1234 cm, 21.9876 cm
b) 34.357 cm, 24.0473 cm
c) 18.426 cm, 15.921 cm
d) 64.2857 cm, 25.7142 cm
Discussion
Explanation: D1 + D2 = 90 cm
\(\frac{D1}{D2}=\frac{50}{20}\) = 2.5
3.5 D2 = 90
D2 = 25.7142 cm
D1 = 64.2857 cm
2. While testing a wheat thresher at recommended throughout, 80 Nm torque is recorded at 750 rpm at the main shaft of the threshing cylinder, which is operated by a 200-mm diameter V pulley. The overload factor and unit mass of V-belt are 1.2 and 0.9 kg/m respectively. At condition of maximum power transfer the maximum tension in V-belt in N is ________
a) 166.55 N
b) 233.78 N
c) 120.06 N
d) 211.23 N
Discussion
Explanation: N = 750 rpm
V = \(\frac{π*0.2*750}{60}\) = 7.854 m/s
M = 0.9 kg/m
Tc = mv2 = 0.9 * (7.854)2
Tc = 55.5165 N
At maximum power transmission
Tmax = 3 Tc
Tmax = 3 * 55.5165 = 166.55 N
3. A V-belt operates at 23.56 m/s peripheral speed. The mass of the belt per unit length is 0.9 kg/m. The value of centrifugal tension is _______
a) 514 N
b) 523 N
c) 500 N
d) 599 N
Discussion
Explanation: V = 23. 56 m/s
M=0.9 kg/m
Tc = mv2 = 0.9 * (23.56)2
Tc = 500 (approx.)
4. Determine the length of cross-belt of connecting two pulleys 4 m apart. The diameters of driving and driven pulleys are 1.25 m and 0.75 m respectively.
a) 12.36 m
b) 11.35 m
c) 14.28 m
d) 13.27 m
Discussion
Explanation: L = 2C + \(\frac{[π(D1+D2)]}{2}+\frac{(D1+D2)^2}{4C} \)
= 2*4 + \(\frac{[π(1.25+0.75)]}{2}+\frac{(2)^2}{4*4}\) = 11.35 m
5. A leather belt 100 mm wide and 10 mm thick with a safe permissible stress of 1.5 MPa is used for transmitting a maximum power of 15 KW. If the density of belt material is 1 g/cm3, the velocity of belt for maximum power transmission will be ________
a) 22.36 m/s
b) 34.13 m/s
c) 24.98 m/s
d) 12.12 m/s
Discussion
Explanation: Area = 100*10*20-6 = 10-3m2
Tmax = Pmax * Area
= 1.5 * 10 * 10-3
Tmax = 1500 N
M = ρ*area
= 1000*10-3 = 1 kg/m
For maximum transmission
Tmax = 3Tc
Tmax= 3mv2
V = \(\sqrt{\frac{Tmax}{3m}} = \sqrt{\frac{1500}{3}} \)
V = 22.36 m/s
6. The primary winding of ignition coil is made of ________
a) 1 mm diameter copper wire
b) 0.8 mm diameter copper wire
c) 0.6 mm diameter copper wire
d) 1.2 mm diameter copper wire
Discussion
Explanation: Primary winding of the transformer is the coil that draws power from the external source. The primary winding of ignition coil is made of 0.8 mm diameter copper wire.
7. Which of the following has highest vaporizing temperature?
a) H.S.D. oil
b) Petrol
c) Water
d) Kerosene
Discussion
Explanation: Vaporization temperature is the temperature at which the liquid is converted into vapor without any change in temperature.
8. What should be the gap of spark plug?
a) 1.2-1.53 mm
b) 2.5-2.85 mm
c) 0.5-0.85 mm
d) 3.15-3.45 mm
Discussion
Explanation: In I.C. engine, the function of spark plug id to make jump of high voltage current and to ignite the mixture, i.e., charge, within the cylinder. It is used in petrol engines. the gap of spark plug should be 2.5-2.85 mm.
9. What is the range of a condenser in an I.C. engine?
a) 0.15-0.45 ΜF
b) 0.1-0.25 ΜF
c) 0.45-0.85 ΜF
d) 0.35-0.65 ΜF
Discussion
Explanation: It is used for quick reduction of magnetic field in the coil to obtain an extremely high voltage current. In internal combustion engines, generally, the range of condensers varies from 0.15 to 0.45 MF
10. Electrolyte used in storage battery consists of _________
a) 25% H2SO4 and 75% distilled water
b) 5% H2SO4 and 95% distilled water
c) 35% H2SO4 and 65% distilled water
d) 45% H2SO4 and 55% distilled water
Discussion
Explanation: When an electrolyte is dissolved in a polar solvent (like water), the resulting solution allows conduction of electricity where in the dissolved electrolyte separates into cations and anions. A storage battery is a battery which is rechargeable. Electrolyte used in storage battery consists of 35% H2SO4 and 65% distilled water.