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businesses are today heated geothermally in Oregon and Idaho any but trace amounts! Hydrogen must therefore be obtained
in the United States, as well as in Hungary, France, Iceland, and by a chemical reaction from such compounds as water. Water
New Zealand. Today, understand that each British thermal unit is a plentiful substance on Earth, and an electric current will
supplied by geothermal energy does not have to be supplied cause decomposition of water into hydrogen and oxygen gas.
by fossil fuels. Tomorrow, you will find geothermal resources Measurement of the electric current and voltage will show that
becoming more and more attractive as the price and the conse-
water + 68,300 calories → hydrogen + oxygen
quences of using fossil fuels continue to increase.
Thus, assuming 100 percent efficiency, the energy needed to
HYDROGEN obtain hydrogen gas from water is exactly equal to the energy
Hydrogen is the lightest and simplest of all the elements, occurring released by hydrogen combustion. So hydrogen cannot be
as a diatomic gas that can be used for energy directly in a fuel cell used to produce energy, since hydrogen gas is not available,
or burned to release heat. Hydrogen could be used to replace natu- but it can be used as a means of storing energy for later use.
ral gas with a few modifications of present natural gas burners. A Indeed, hydrogen may be destined to become an effective so-
big plus in favor of hydrogen as a fuel is that it produces no pol- lution to the problems of storing and transporting energy de-
lutants. In addition to the heat produced, the only emission from rived from solar energy sources. In addition, hydrogen might
burning hydrogen is water, as shown in the following equation: serve as the transportable source of energy, such as that needed
for cars and trucks, replacing the fossil fuels. In summary,
hydrogen + oxygen → water + 68,300 calories
hydrogen has the potential to provide clean, alternative energy
The primary problem with using hydrogen as an energy for a number of uses, including lighting, heating, cooling, and
source is that it does not exist on or under Earth’s surface in transportation.

SUMMARY

Work is defined as the product of an applied force and the distance fuel that contains impurities and sulfur. Controlling air pollution from
through which the force acts. Work is measured in newton-meters, a burning coal is costly. Water power and nuclear energy are used for the
metric unit called a joule. Power is work per unit of time. Power is mea- generation of electricity. An alternative source of energy is one that is
sured in watts. One watt is 1 joule per second. Power is also measured different from the typical sources used today. Alternative sources could
in horsepower. One horsepower is 550 ft⋅ lb/s. be solar, geothermal, or hydrogen.
Energy is defined as the ability to do work. An object that is el-
evated against gravity has a potential to do work. The object is said to
have potential energy, or energy of position. Moving objects have the
ability to do work on other objects because of their motion. The energy SUMMARY OF EQUATIONS
of motion is called kinetic energy. 3.1
Work is usually done against inertia, gravity, friction, shape, or
work = force × distance
combinations of these. As a result, there is a gain of kinetic energy, po-
W = Fd
tential energy, an increased temperature, or any combination of these.
Energy comes in the forms of mechanical, chemical, radiant, electrical, 3.2 _
work
or nuclear. Potential energy can be converted to kinetic, and kinetic power = time
can be converted to potential. Any form of energy can be converted to W _

any other form. Most technological devices are energy-form converters P =
t
that do work for you. Energy flows into and out of the surroundings, 3.3
but the amount of energy is always constant. The law of conservation of gravitational potential energy = weight × height
energy states that energy is never created or destroyed. Energy conver- PE = mgh
sion always takes place through heating or working.
3.4
The basic energy sources today are the chemical fossil fuels (petro- 1 _ 2
kinetic energy = (mass) (velocity)
leum, natural gas, and coal), nuclear energy, and hydropower. Petroleum 2
and natural gas were formed from organic material of plankton, tiny 1 _ 2

KE = mv
free-floating plants and animals. A barrel of petroleum is 42 U.S. gal- 2
3.5
lons, but such a container does not actually exist. Coal formed from
plants that were protected from consumption by falling into a swamp. acceleration due
final velocity = square root of (2 × to gravity × height of fall)
The decayed plant material, peat, was changed into the various ranks of

coal by pressure and heating over some period of time. Coal is a dirty v = √ 2gh
f
80 CHAPTER 3 Energy 3-20