What happens to the piston during the intake phase of the Otto cycle?

During the intake phase of the Otto cycle, the piston moves down within the cylinder. This downward motion creates a vacuum, which allows the air-fuel mixture to be drawn into the combustion chamber from the intake manifold. As the piston pulls down, the pressure inside the cylinder decreases, facilitating the entry of the air-fuel mixture through the open intake valve. This is a critical step in preparing the engine for combustion, as it ensures that there is a sufficient amount of fuel and air available for the next phase of the cycle.

The other options describe actions that occur at different stages of the engine cycle. For instance, compressing the mixture occurs during the compression phase, while pushing exhaust gases happens during the exhaust stroke, when the piston moves back up after combustion. The stationary piston does not occur during the intake phase since movement is necessary for drawing in the mixture. Therefore, the correct understanding of the piston motion during the intake phase is essential for grasping how the Otto cycle operates effectively.