21.3 Electrical Energy Generation and Transmission
Reading Focus
Key Concepts
How is voltage induced in a conductor?- Name two types of generators.
- How can a transformer change voltage and current?
- What are some sources of electrical energy in the United States?
Vocabulary
electromagnetic induction
generator
transformer
turbine
Reading Strategy
Sequencing Copy the flowchart below. As you read, complete it to show how a step-up transformer works. Then make a similar flowchart for a step-down transformer.
Think about how electrical energy affects a city. Traffic lights change colors to control the flow of cars. Flashing neon lights advertise businesses. Subways use electrical energy to move from place to place. People use electrical energy to warm their homes, cook their suppers, and wash their clothes. At night, lights shine from the windows of tall buildings as shown in Figure 12. Where does all the electrical energy come from?
Generating Electric Current
All of the electrical energy that moves subway trains, lights buildings, and powers factories comes from the two aspects of the electromagnetic force. You already know that an electric current produces a magnetic field. However, you may not know that a magnetic field can be used to produce an electric current. Electromagnetic induction is the process of generating a current by moving an electrical conductor relative to a magnetic field. Recall that electrical conductors are materials through which charge can easily flow.
Figure 12 Photographs of large cities, such as Seattle, Washington, are visible reminders of how much people rely on electrical energy.
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