Question 21Motor Plants - Assistant Engineer
70% to passIn the pressure-volume diagram, shown in the illustration, what is indicated to have occurred by the line connecting points 'd' and 'e'? Illustration MO-0035
AThe combustion gases have expanded.
BThe crankshaft has rotated 90°.
CPressure and volume have increased.
DThe fuel/air charge is compressed.
AI Explanation
The correct answer is A) The combustion gases have expanded. The line connecting points 'd' and 'e' on the pressure-volume diagram represents the expansion stroke of the engine cycle. During this stroke, the combustion gases produced from the fuel/air charge ignition expand, pushing the piston down and creating the power to rotate the crankshaft. The other options are incorrect because: B) The crankshaft has rotated 90° is not directly indicated by the line between 'd' and 'e'; C) Pressure and volume have increased is the opposite of what happens during the expansion stroke; and D) The fuel/air charge is compressed occurs earlier in the engine cycle, not during the expansion stroke.
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