Science 8

1. Electrical Energy Transfer Science 8

2. How do you get electricity? • It involves a lot more than just flipping a switch or plugging something into an outlet! • If you have ever “lost “ power, you have been reminded of how much you rely on electricity! • Electricity was first used to illuminate a street and a business in 1886! It was a few more years before scientists figured out how to distribute it over a distance and safely into homes. • Think about how far people have come in less than 120 years.

3. Vocabulary • Terms to know: • Voltage- the pressure that causes electrons to flow. • Volt- a unit measure of voltage. • Current- The flow of electrons through a conductor (similar to water through a pipe). • Watt (W)- a unit of electrical power. Electrical power measured in Watts is equal to the voltage times the current. (Kilowatt= (kW)= 1000 Watts) • Joule (J)- A joule is a measurement of electrical energy. 1 joule is equal to 1 watt of power for 1 second of time (watts x time = joules). • Power-The rate of energy use. In electricity, energy is produced by moving electrical current through an electrical load. Power used over a period of time yields energy.

4. Where does it all start? The power plant! Imagine this is the Jack Watson plant… our extension of Mississippi Power. The majority of power plants (like Jack Watson) use coal as a source of energy. The coal is burned to heat water. The heated water creates steam. The steam turns the turbine which turns the generator which creates the electricity that is sent out of the plant.

5. Information about the electricity produced at the power plant: • The electricity produced at the power plant is 3-phase AC power. This means they are producing 3 different phases of AC power at the same time offset at 120 degrees. It would look like this: • Your home only uses 1 phase. So why do they produce 3 phases? 3 x 120o =360o (a circle). This means that there isalways a current at peak performance and never a slump in energy production.

6. Where does it go from there? • From the power plant, electricity is sent to a “step-up” transformer. • Because it takes a lot of energy to send electricity out to homes and businesses, the power behind it (the volts) have to be “stepped-up” (or increased) so it can make the trip. A step-up transformer

7. FYI: a single transmission can travel up to 300 miles from the plant! • After leaving the step-up transformer, the electricity will travel along wires attached to power poles. There are two main types of power poles: Low voltage You typically see these in neighborhoods , along streets orhighways… anywhere with places reasonably close together. High voltage you see these close to plants, or anywhere the electricity being transmitted a longer distance.

8. Before it reaches you… • We stepped-up the power behind the electricity so it could travel, that power needs to be taken back down before it enters your house. This usually happens at a substation. At the substation, the power goes from “transmission” to “distribution”. It is taken down to safe levels and sent in different directions.

9. Get on the bus… • The substation has a “bus”. It may not look anything like the bus you ride on, it does pretty much the same job. It sends the electricity where it needs to go. Notice all of the wires going in many different directions…. Anyone want some power?

10. In your home… • Even though the power behind the electricity has been “stepped-down” by the time it is traveling on the wires down your street, it is still about 7,200 volts. The electricity has to be stepped-down again because your house runs on 120-240 volts. You may have noticed that every few power poles on your street have something that looks like this on them. This is another type of transformer that takes the electricity in the wire down to a safe level before it enters your home.