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224 Engineering Fundamentals
In coal, nuclear, and natural gas power plants,
tremendous amounts of steam are generated. This
steam is used to turn massive turbines, creating
rotary motion that spins a generator. In hydroelec-
tric dams, falling water is used to turn turbines.
These turbines then turn generators. In wind
farms, turbine blades are turned by the wind to
create rotary motion for the generator.
See Workbook Activity 11-1 to learn how
magnets and motion can be used to
generate electricity.
Chemical Action
Cells create electrical energy using a chemi-
cal action. A battery is an electrical connection of
two or more cells. An electrode is a solid conduc-
tor through which electricity enters or leaves a
medium. When two electrodes made of different
materials are placed in an electrolyte, electrons
gather on the negative terminal and a voltage
builds up between the electrodes. The electrolyte
acts chemically on the electrodes and conducts
electrons between the electrodes. Disposable
batteries are called primary cells and batteries
that can be recharged are called secondary cells.
Making a cell can be as simple as soaking a
paper towel in salt water and placing it between
two unlike pieces of metal. A very small volt-
age can be read between the metals. Figure 11-7
shows a very simple cell that you can make.
Magnetism
Magnets are important in the area of electri-
cal engineering because they are used to generate
electricity. A magnet is usually made of iron, steel,
or a mixture of metals. A magnet contains polari-
ties. Polarity describes the direction of a magnetic
field. The magnetic field is strongest at a magnet’s
poles, each in the direction opposite of the other. A
magnet has two poles. The earth is considered a
magnet with two poles: north and south.
Every magnet has two poles. If you cut a magnet
in half, each piece would then have two poles. Like
poles repel each other, while opposite poles attract.
For example, the north pole of one magnet will attract
the south pole of another magnet. However, the north
poles of two magnets will push away from each other.
Every magnet has a magnetic field created by its
poles. A stronger magnetic field is created between
two magnets with opposite poles. The field surrounds
the magnets and pulls them closer together. The
magnetic fields of two magnets with similar poles
are different. Because the magnets repel each other,
their magnetic fields stay as they are.
Science
Goodheart-Willcox Publisher
Figure 11-7. 
This is a basic cell. Unlike metals are separated by a paper towel soaked in salt water.
Paper towel soaked in salt water
between two unlike pieces of metal
Copper
Zinc