1. With dissociation, peak temperature is obtained ___________
a) at the stoichiometric ratio
b) when the mixture is slightly lean
c) when the mixture is slightly rich
d) none of the mentioned
Explanation: when the mixture is slightly rich
2. With dissociation the exhaust gas pressure ____________
a) decreases
b) increases
c) no effect
d) increases upto certain air fuel ratio and then decreases
Explanation: With dissociation the exhaust gas pressure decreases
3. For a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure _____________
a) decreases
b) increases
c) initially increases then decreases
d) remains more or less same
Explanation: initially increases then decreases
4. When the mixture is lean ___________
a) efficiency is less
b) power output is less
c) maximum temperature and pressure are higher
d) all of the mentioned
Explanation: Power output is less when the mixture is lean.
5. For a compressor process with variable specific heat the peak temperature and pressure are ____________
a) lower
b) higher
c) no effect
d) none of the mentioned
Explanation: For a compressor process with variable specific heat the peak temperature and pressure are lower
6. Time loss factor in Actual Cycle is due to ______________
a) progressive combustion
b) heat loss through cylinder walls
c) gas leakage
d) friction
Explanation: progressive combustion
7. If the spark timing is at TDC, the work is _____________
a) more
b) less
c) equal
d) none of the mentioned
Explanation: If the spark timing is at TDC, the work is less as the peak pressure is low.
8. When the spark is advanced, the work output is less as ____________
a) the peak pressure is low
b) the peak temperature is low
c) additional work is required to compress the burning gas
d) frictional losses increase
Explanation: When the spark is advanced, the work output is less as additional work is required to compress the burning gas.
9. Optimum spark timing gives __________________
a) higher mean effective pressure
b) higher efficiency
c) higher mean effective pressure and higher efficiency
d) none of the mentioned
Explanation: Optimum spark timing gives higher mean effective pressure and higher efficiency
10. The major loss in a S.I. engine is due to __________
a) exhaust blow down
b) pumping
c) incomplete combustion
d) variation in specific heat and chemical equilibrium
Explanation: The major loss in a S.I. engine is due to variation in specific heat and chemical equilibrium while the major loss in a C.I. engine is loss due to incomplete combustion.