25.3. Generating and Using Electricity http://www.ck12.org
25.3 Generating and Using Electricity
Lesson Objectives
- Describe electromagnetic induction.
- Explain how electric generators and transformers work.
- State the roles of generators and transformers in electrifying the home.
Lesson Vocabulary
- electric generator
- electric transformer
- electromagnetic induction
- Faraday’s law
Introduction
You probably use many electric devices every day, including lights and appliances such as hair dryers and mi-
crowaves. Where does the electricity come from to power these devices? The answer is magnetic fields.
From Magnets to Electricity
Just about a decade after Oersted discovered that electric current produces a magnetic field, an English scientist
named Michael Faraday discovered that the reverse is also true. A magnetic field produces an electric current, as
long as the magnetic field is changing. This is calledFaraday’s law.
Electromagnetic Induction
The process of generating electric current with a changing magnetic field is calledelectromagnetic induction. It
occurs whenever a magnetic field and an electric conductor, such as a coil of wire, move relative to one another. As
long as the conductor is part of a closed circuit, current will flow through it whenever it crosses magnetic field lines.
One way this can happen is pictured inFigure25.9. It shows a magnet moving inside a wire coil. Another way is
for the coil to move instead of the magnet.
You can watch an animated version ofFigure25.9 at this URL: http://jsticca.wordpress.com/2009/09/01/the-magn
et-car/.