Energy Use Investigation 9.1:

Automobile Energy Transformations

As you drive, you are manipulating at least four types of energy: electrical, chemical, mechanical (motion), and thermal (heat). Energy from the driver turns the key and presses the pedals, buttons, and switches, but that energy does not make the car go. Here is a list of events that occur in the car. Each one is an energy transformation.

When You Turn the Key

• The battery makes electricity for the electric starter motor.

• Electric starter motor turns the engine crank.

When You Step on the Accelerator

• The fuel pump feeds gasoline to the carburetor.

• The carburetor mixes gas with air to create a spray that goes into the cylinder.

• The battery sends electricity to the spark plugs.

• The spark plug ignites the mixture of gasoline and air in the cylinder.

• The gasoline-air mixture explodes.

• The expanding hot gases from the combustion push the piston down.

• The piston turns the crank shaft.

• The clutch connects the crank shaft to the transmission.

• The transmission turns the drive shaft.

• The drive shaft spins gears that turn the wheels.

• Wheels push on the road, propelling the car forward.

• Air resistance pushes back against the car. Meanwhile

• The engine turns the generator (or alternator).

• The generator produces electricity.

• The electricity charges the battery.

• The electricity runs the lights, fuel pump, radio, and other devices.

When You Step on the Brake

• Brake shoes rub the brake drum in the wheel.

• Friction between the brake drum and the wheel stops the car.

Question 9.1
Which one of the events is the transformation from chemical energy to heat energy?
[It’s not the first one on the list, but it is the one that really makes the whole system go.]
Follow the energy from transformation to transformation,
starting with “The gasoline-air mixture explodes,”
and answer the following questions.

Question 9.2
Where does the energy go from there?

Question 9.3
At which points does the energy branch off in more than one direction?

Question 9.4
Where does all the energy eventually go?


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