Inside a four-stroke engine

In the picture

1. 1Intake valve: opens to let air and fuel into the cylinder.
2. 2Piston: moves up to compress the mixture, then is pushed down by the burning gases.
3. 3Spark plug: makes a spark that ignites the compressed mixture.
4. 4Exhaust valve: opens to let burned gases leave the cylinder.
5. 5Crankshaft: turns the piston’s up-and-down motion into rotation.

Examples

• A petrol car engine moving along a road.
• A petrol lawnmower engine cutting grass.

Quiz: Inside a four-stroke engine (Age 13)

1. 1

   Which list shows the four strokes in the correct order?

   • Intake, compression, power, exhaust
   • Intake, power, compression, exhaust
   • Compression, intake, exhaust, power
2. 2

   What does the crankshaft do?

   • It changes the piston’s up-and-down motion into spinning motion.
   • It lets air and fuel into the cylinder.
   • It makes the spark that ignites the mixture.
3. 3

   What is the spark plug’s job?

   • It opens to let burned gases leave the cylinder.
   • It changes the piston’s up-and-down motion into spinning motion.
   • It makes a spark that ignites the compressed mixture.

The answers, each with its explanation, are in the app. This quiz is free there while the lesson is in the free week.