Electromagnetism Electromagnetism

Section
3
electromagnetic induction
generator
transformer
◆ Explain how a magnetic field
can produce an electric current.
◆ Explain how electromagnetic
induction is used in a generator.
◆ Compare step-up and step-down
transformers.
Figure 20 Faraday’s Setup
468
One wire was wound around
one half of an iron ring.
A battery supplied an electric current
to the wire, making an electromagnet.
Chapter 18
Electricity from Magnetism
When you use an electric appliance or turn on a light in your
home, you probably don’t think about where the electrical
energy comes from. For most people, an electric power company
supplies their home with electrical energy. In this section,
you’ll learn how a magnetic field can produce an electric
current and how power companies use this process to supply
electrical energy.
Electric Current from a Magnetic Field
After Oersted discovered that an electric current could produce
a magnetic field, scientists began to wonder if a magnetic field
could produce an electric current. In 1831, two scientists—
Michael Faraday, from Great Britain, and Joseph Henry, from
the United States—independently solved this problem.
Although Henry was the first to make the discovery, Faraday’s
results are better known because Faraday published his results
first and reported them in greater detail.
Faraday’s Failure? In his experiments, Faraday used a setup
similar to the one shown in Figure 20. Faraday hoped that the
magnetic field created by the electromagnet would create—or
induce—an electric current in the second wire. But no matter
how strong the electromagnet was, no electric current could
be produced in the second wire.
A second wire was wound around
the other half of the iron ring.
A galvanometer measured any current produced
in the second wire by the magnetic field.
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