http://www.ck12.org Chapter 5. Energy
- A step-down transformer decreases the voltage of the current so it can be distributed safely to businesses and
homes. A high-voltage power line may have 750,000 volts, whereas most home circuits have a maximum of
240 volts. Therefore, one or more step-down transformers are needed to decrease the voltage of current before
it enters homes.
Q:Assume that a home needs a 14-volt circuit for a light and a 120-volt circuit for a microwave oven. If the main
power line entering home has 240 volts, what can you infer about the home’s electrical system?
A:The home’s electrical system must have step-down transformers that lower the voltage for some of the home’s
circuits.
Summary
- The electrical grid is the entire electrical system that generates, transmits, and distributes electric power
throughout a region or country. It includes power plants, transmission lines, and electric substations. - Power plants are where electric power originates. They have electric generators that generate electric current
through electromagnetic induction. - Transmission lines carry electric current from power plants to substations and from substations to homes and
other places where electric power is needed. - Electric substations have step-up or step-down transformers to increase or decrease the voltage of current as
needed.
Vocabulary
- electrical grid: Entire electrical system that generates, transmits, and distributes electric power throughout a
region or country.
Explore More
At the following URL, read Chapter 7 of the Energy Story. Be sure to read the “Energy Safety Note!” at the bottom
of the Web page. Then answer the questions below.
http://www.energyquest.ca.gov/story/chapter07.html
- What is the voltage of current produced at power plants?
- Why is the voltage increased before it is transmitted through the electrical grid?
- Some of the electricity that is transmitted is lost. Explain why.
- What happens to electricity when it reaches substations near businesses and homes?
- Some new distribution lines are underground rather than overhead. What is a pro of underground lines?
- List two tips for staying safe around the electrical grid.
Review
- Identify the components of an electrical grid.
- What is the source of power in an electrical grid?
- Explain why an electrical grid must have electric transformers.
- If lightning strikes a transformer, it will cause power outages. Which lightning strike is likely to affect the most
electric power customers: a strike to a step-down transformer on an electric pole or a strike to a step-down
transformer in an electric substation?