Question

Think Critically:

A lightbulb converts 10 percent of the electrical energy it uses into radiant energy. Make a hypothesis about the other form of energy produced.

Answer 1

Plants Almost 90 percent of the electrical

energy generated in the United States is produced by Oil

nuclear and fossil fuel power plants, as shown in 3%

Figure 15. Other types of power plants include hydro- Coal Gas
51%
electric (hi droh ih LEK trihk) and wind. Hydroelec- 14%

tric power plants transform the kinetic energy of Hydro
moving water into electrical energy. Wind power 9%
plants transform the kinetic energy of moving air into
electrical energy. In these power plants, a generator Nuclear Other
converts the kinetic energy of moving water or wind 20% renewable
3%

to electrical energy.

To analyze the energy transformations in a power

plant, you can diagram the energy changes using arrows. A coal- Figure 15 The graph shows

burning power plant generates electrical energy through the fol- sources of electrical energy in the

lowing series of energy transformations. United States.

chemical thermal kinetic kinetic electrical Name the energy source that you
energy → energy → energy → energy → energy think is being used to provide the
electricity for the lights overhead.
of coal of water of steam of turbine out of

generator

Nuclear power plants use a similar series of transformations.
Hydroelectric plants, however, skip the steps that change water
into steam because the water strikes the turbine directly.

Summary Self Check

Changing Forms of Energy 1. Describe the conversions between potential and
kinetic energy that occur when you shoot a basketball
• Heat usually is one of the forms of energy pro- at a basket.
duced in energy transformations.
2. Explain whether your body gains or loses thermal
• The law of conservation of energy states that energy if your body temperature is 37°C and the
energy cannot be created or destroyed; it can temperature around you is 25°C.

only change form. 3. Describe a process that converts chemical energy to
thermal energy.
• The total energy doesn’t change when an
energy transformation occurs. 4. Think Critically A lightbulb converts 10 percent of
the electrical energy it uses into radiant energy.
• As an object rises and falls, kinetic and poten- Make a hypothesis about the other form of energy
tial energy are transformed into each other, produced.

but the total energy doesn’t change. 5. Use a Ratio How many times greater is the amount of
electrical energy produced in the United States by
Generating Electrical Energy coal-burning power plants than the amount produced
by nuclear power plants?
• A generator converts kinetic energy into elec-
trical energy.

• Burning fossil fuels produces thermal energy
that is used to boil water and produce steam.

• In a power plant, steam is used to spin a tur-
bine which then spins an electric generator.

Answer 2

When you touch a light bulb, you can notice that the lightbulb is actually really hot. This is because some of the energy that reaches the lightbulb is transformed into heat, if 10% of the electrical energy is used to make radiant energy (light ) then the other 90% is dissipated as heat.