# IC Engine Questions and Answers – Effects of Operating Variables

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This set of IC Engines Multiple Choice Questions & Answers (MCQs) focuses on “Effects Of Operating Variables”.

1. The fuel air cycle efficiency _______________ with the compression ratio.
a) increases
b) decreases
c) remains same
d) none of the mentioned

Explanation: As the compression ratio is increased the efficiency of fuel air cycle also increases as there is more scope of expansion work.

2. Fuel ratio is defined as the ratio of actual fuel air ratio to chemically correct fuel air ratio on mass basis.
a) True
b) False

Explanation: Actually, equivalence ratio is defined as the ratio of actual fuel air ratio to chemically correct fuel air ratio on mass basis.

3. The maximum pressure and maximum temperature ____________ with compression ratio.
a) increases
b) decreases
c) remains same
d) none of the mentioned

Explanation: Since, the temperature and pressure at the end of compression are higher, so, as a result the maximum pressure and maximum temperature increases with compression ratio.
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4. As the mixture is made lean the temperature rise due to combustion will be lowered.
a) True
b) False

Explanation: When the mixture is made lean the temperature rise due to combustion will be lowered as a result of reduced energy input per unit mass of mixture.

5. Fuel air ratio affects maximum power output of the engine due to ____________
a) higher specific heats
b) chemical equilibrium losses
c) higher specific heats and chemical equilibrium losses
d) none of the mentioned

Explanation: Due to both higher specific heats and chemical equilibrium losses, the fuel air ratio affects the maximum power output of the engine.
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6. Mean effective pressure at a given compression ratio is maximum when the air fuel ratio is?
a) higher than stoichiometric
b) lower than stoichiometric
c) equal to stoichiometric
d) none of the mentioned

Explanation: When the air fuel ratio is lower than stoichiometric then only the mean effective pressure at a given compression ratio is maximum.

7. For a compression process with variable specific heat the peak temperature and pressure are _____________ as compared to constant specific heat.
a) lower
b) higher
c) no effect
d) none of the mentioned

Explanation: The peak temperature and pressure are lower for a compression process with variable specific heat as compared to constant specific heat.

8. Cycles with lean to very lean mixture tend towards ____________
a) practice cycles
b) fuel air cycles
c) air standard cycles
d) none of the mentioned

Explanation: All the cycles mentioned above operates only on high mixtures.

9. 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 directly proportional to mixture, so when the mixture is lean, the power output is less and vice-versa.

10. For a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure ____________
a) increases
b) decreases
c) initially increases and then decreases
d) remains more or less the same

Explanation: To get a stable condition, for a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure.

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