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People Behind the Science

James Prescott Joule (1818–1889)

ames Joule was a British physicist who attitudes, however, and Kelvin subsequently
Jhelped develop the principle of conserva- used Joule’s practical ability to great advan-
tion of energy by experimentally measuring tage. By 1850, Joule was highly regarded by
the mechanical equivalent of heat. In recog- other scientists and was elected a fellow of
nition of Joule’s pioneering work on energy, the Royal Society. Joule’s own wealth was
the SI unit of energy is named the joule. able to fund his scientific career, and he
Joule was born on December 24, 1818, never took an academic post. His funds
into a wealthy brewing family. He and his eventually ran out, however. He was awar ded
brother were educated at home between a pension in 1878 by Queen Victoria, but
1833 and 1837 in elementary math, natu- by that time, his mental powers were going.
ral philosophy, and chemistry, partly by the He suffered a long illness and died on James Prescott Joule
English chemist John Dalton (1766–1844) October 11, 1889.
(see p. 204). Joule was a delicate child and Joule realized the importance of accu- evidence. He showed that the same relation-
very shy, and apart from his early educa- rate measurement very early on, and exact ship could be examined experimentally and
tion, he was entirely self-taught in science. data became his hallmark. His most active that the ratio of equivalence of the different
He does not seem to have played any part in research period was between 1837 and forms of energy did not depend on how one
the family brewing business, although some 1847. In a long series of experiments, he form was converted into another or on the
of his first experiments were done in the studied the relationship between electrical, materials involved. The principle that Joule
laboratory at the brewery. mechanical, and chemical effects and heat, had established is that energy cannot be cre-
Joule had great dexterity as an experi- and in 1843, he was able to announce his de- ated or destroyed but only transformed.
menter, and he could measure temperatures termination of the amount of work required Joule lives on in the use of his name to
very precisely. At first, other scientists could to produce a unit of heat. This is called the measure energy, supplanting earlier units
not believe such accuracy and were skepti- mechanical equivalent of heat (4.184 joules such as the erg and calorie. It is an appropri-
cal about the theories that Joule developed per calorie). ate reflection of his great experimental abil-
to explain his results. The encouragement One great value of Joule’s work was the ity and his tenacity in establishing a basic
of Lord Kelvin from 1847 changed these variety and completeness of his experimental law of science.

Source: Modified from the Hutchinson Dictionary of Scientific Biography. © Research Machines plc 2003. All Rights Reserved. Helicon Publishing is a division of Research Machines.

collected under special conditions millions of years ago. Thus, Most of the coal mined today is burned by utilities to
petroleum, natural gas, and coal are called fossil fuels. Fossil generate electricity (about 80 percent). The coal is ground to a
fuels contain the stored radiant energy of organisms that lived face-powder consistency and blown into furnaces. This greatly
millions of years ago. increases efficiency but produces fl y ash, ash that “flies” up the
The first thing to happen in the formation of coal was that chimney. Industries and utilities are required by the U.S. Clean
plants in swamps died and sank. Stagnant swamp water protected Air Act to remove sulfur dioxide and fly ash from plant emis-
the plants and plant materials from consumption by animals and sions. About 20 percent of the cost of a new coal-fired power
decomposition by microorganisms. Over time, chemically al- plant goes into air pollution control equipment. Coal is an
tered plant materials collected at the bottom of pools of water in abundant but dirty energy source.
the swamp. This carbon-rich material is peat (not to be confused
with peat moss). Peat is used as a fuel in many places in the world.
The flavor of Scotch (whisky) is the result of the peat fires used to MOVING WATER
brew the liquor. Peat is still being produced naturally in swampy Moving water has been used as a source of energy for thousands
areas today. Under pressure and at high temperatures peat will of years. It is considered a renewable energy source, inexhaustible
eventually be converted to coal. There are several stages, or ranks, as long as the rain falls. Today, hydroelectric plants generate
in the formation of coal. The lowest rank is lignite (brown coal), about 3 percent of the nation’s total energy consumption at about
and then subbituminous, then bituminous (soft coal), and the 2,400 power-generating dams across the nation. Hydropower
highest rank is anthracite (hard coal). furnished about 40 percent of the United States’ electric power
Each rank of coal has different burning properties and a in 1940. Today, dams furnish 9 percent of the electric power. It is
different energy content. Coal also contains impurities of clay, projected that this will drop even lower, perhaps to 7 percent in
silt, iron oxide, and sulfur. The mineral impurities leave an ash the near future. Energy consumption has increased, but hydro-
when the coal is burned, and the sulfur produces sulfur dioxide, power production has not kept pace because geography limits
a pollutant. the number of sites that can be built.

76 CHAPTER 3 Energy 3-16