During which strokes does the piston move downward in a four-stroke internal combustion engine?

intake and exhaust

compression and exhaust

power and intake

compression and power

Answer: The correct answer is "power and intake".

Explanation:

A four stroke internal combustion engine consists of four distinct piston strokes. These four strokes are: intake, power, exhaust and compression.

In the exhaust stroke, it squeezes out the gases. These gases created during the combustion stroke. Here, the piston moves upward.

In the intake stroke, the piston moves downward. It creates partial vacuum.

In the compression stroke, the air is compressed to top of cylinder by piston. Here, the piston moves upward.

In the power stroke, ignited fuel mixture expands. It pushes the piston downward.

Therefore, the correct option is "power and intake".