Final answer:
The spark plug in a four-stroke internal combustion engine sparks once per cycle during the combustion stroke, which is one of the four strokes of the Otto cycle.
Step-by-step explanation:
The question pertains to the four-stroke internal combustion engine and the functioning of the spark plug within it. A four-stroke engine operates through an Otto cycle, which includes four distinct strokes: intake, compression, combustion (power), and exhaust. As the name suggests, there are four strokes in one cycle.
During the intake stroke, the spark plug does not spark as the engine is simply drawing in the air-fuel mixture. The compression stroke also does not involve a spark, as the air-fuel mixture is being compressed to prepare for ignition. The combustion (power) stroke is where the spark plug does its job by igniting the compressed air-fuel mixture, resulting in the single spark needed for that cycle. Finally, during the exhaust stroke, the burnt gases are expelled and there is no need for a spark.
Thus, the answer to the question, "How many times does the spark plug spark during the 4 cycles?" is that the spark plug sparks once per cycle. Distinctively, in the Otto cycle, this happens during the third stroke, which is the combustion or power stroke.