1. What is the basic reaction in the battery of the ignition system?
a) PbO5 + Pb + 4H2SO4 = 4PbSO2 + 4H20
b) 2PbO2 + 2H2SO4 = 2PbO + 2SO4 + 2H2O + O2
c) PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O
d) PbO2 + 2H2SO4 = 2PbSO4 + 2H2O
Discussion
Explanation: Sulphuric acid is used as an electrolyte, which contains about 35% sulphuric acid and 65% water. The specific gravity at full charge is about 1.270, while at complete discharge it is about 1.10.
2. Which of the following is not a feature of the spark plug?
a) Varies from 0.5 to 0.85 mm
b) Used in cold engines
c) Dissipates the heat very quickly, it used for hot engine
d) Ratio of turns in primary and secondary is 1:100
Discussion
Explanation: The last option is a feature of the ignition coil in which 6 or 12-volt current is fed in the primary winding and from the secondary winding voltage to the tune of 2000 volt is tapped.
3. What is the co-efficient of friction for lubricant?
a) Cf = \(\frac{ZN}{P} \)
b) Cf = \(\frac{PN}{Z} \)
c) Cf = \(\frac{ZP}{N} \)
d) Cf = ZPN
Discussion
Explanation: The lubricated friction depends on the operating conditions such as the sliding speed, lubricant viscosity, temperature etc. In the formula, Z is the viscosity or oil thickness, N is the surface speed and P is the pressure caused by the weight.
4. What is the Carnot Cycle Efficiency?
a) η = 1- QC/QH
b) η = QC/QH
c) η = QC/QH -1
d) η = QH/QC
Discussion
Explanation: Since energy is conserved according to the first law of thermodynamics and energy cannot be converted to work completely, the heat input, QH, must be equal to the work done, W, plus the heat that must be dissipated as waste heat QC, into the environment.
5. What is the Carnot efficiency for a coal–fired power plant?
a) 65%
b) 74%
c) 56%
d) 90%
Discussion
Explanation: In modern day coal fire power plant, the temperature of high pressure steam (Thot) would be about 400° C and Tcold = 20° C.
η = 1−\(\frac{293}{673}\)
η = 56%.
6. What is the formula for indicated mean effective pressure?
a) Pi = \(\frac{(Area \, of \, indicator \, diagram)}{Length \, of \, indicator \, diagram \, * \, spring \, scale \, index} \)
b) Pi = \(\frac{(Length\, of \, indicator \, diagram \, * \, spring\, scale \,index)}{Area\, of \,indicator \, diagram} \)
c) Pi = \(\frac{Length \, of \, indicator \, diagram}{Area \,of \,indicator\, diagram \, * \, spring \, scale \, index} \)
d) Pi = \(\frac{Spring \, scale \, index}{Area \, of \, indicator \, diagram \, * \, Length \, of \, indicator \, diagram} \)
Discussion
Explanation: Indicated mean effective pressure is the algebraic sum of the mean pressures acting on the piston during each stroke over one complete cycle. It is measured through indicator diagram drawn with the help of an engine indicator.
7. What is value of ‘n’, if there is no missing cycle, in brake power when it is applied as double acting, two stroke engines?
a) 2N
b) N
c) N/2
d) 4N
Discussion
Explanation: Brake power is the actual work output of an engine or the actual work available at the crankshaft or flywheel. It is also called shaft power and is given by:
B.P.= \(\frac{2πnT}{60000}\) KW.
8. What is the formula for specific fuel consumption (i.s.f.c.)?
a) i.s.f.c.=\(\frac{60 I.P.}{Wf} \)
b) i.s.f.c.=\(\frac{60 Wf}{I.P.} \)
c) i.s.f.c.=\(\frac{120 Wf}{I.P.} \)
d) i.s.f.c.=\(\frac{120 I.P.}{Wf} \)
Discussion
Explanation: The total consumption of fuel by an engine under test conditions in a given time is determined by measuring its volume or weight. The specific fuel consumption is defined as the total consumption per hour or per KW developed.
9. What is the name of the phenomenon caused in a governor in which the speed of the engines fluctuates continuously above and below the mean speed?
a) Firing interval
b) Air-Supply measurement
c) Sensitiveness of Governor
d) Governor hunting
Discussion
Explanation: A governor is said to be hunt if the speed of the engines fluctuates continuously above and below the mean speed. This is caused by a too sensitive governor which changes the fuel supply by a large amount when a small change in the speed of rotation takes place.
10. What is the formula of controlling force (Fc) of a governor?
a) Fc = n2 ω r
b) Fc = m ω r
c) Fc = m ω2 r
d) Fc = m ω r2
Discussion
Explanation: In case of governor running at a steady speed, the inward force acting on the rotating balls is known as controlling force. It is equal and opposite to the centrifugal reaction. The formula of controlling force (Fc) of a governor is Fc= m ω2 r.