http://www.ck12.org Chapter 5. Energy
- A piston inside the cylinder moves upward, compressing the fuel-air mixture in the closed cylinder. The
mixture is now under a lot of pressure and very warm. - A spark from a spark plug ignites the fuel-air mixture, causing it to burn explosively within the confined space
of the closed cylinder. - The pressure of the hot gases from combustion pushes the piston downward.
- The piston moves up again, pushing exhaust gases out of the cylinder through another valve.
- The piston moves downward again, and the cycle repeats.
You can watch animations of internal combustion engines in action at these URLs: http://auto.howstuffworks.co
m/engine1.htm and http://www.familycar.com/Engine.htm.
FIGURE 5.43
Q:The internal combustion engine converts thermal energy to another form of energy. Which form of energy is it?
A:The engine converts thermal energy to kinetic energy, or the energy of a moving object—in this case, the moving
piston.
How Energy from the Engine Turns the Wheels
In a car, the piston in the engine is connected by the piston rod to the crankshaft. The crankshaft rotates when the
piston moves up and down. The crankshaft, in turn, is connected to the driveshaft. When the crankshaft rotates, so
does the driveshaft. The rotating driveshaft turns the wheels of the car.