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Electric Motors: The Green Machines!
Grades 4-6

Overview

It is very important for students to understand that scientists and inventors come from all backgrounds. History teaches us that many scientists did not do well in school, and that they needed an alternative education to succeed in life. Michael Faraday received his education through on-the-job ("hands-on") training, and became one of the world's most famous "experimental" scientists. In the first part of the lesson students will learn Faraday's law of electromagnetic induction during the assembly of an electric generator. The second part of the lesson examines illustrations of a variety of power sources that can be used to operate generators and electric motors.
ITV Series
3-2-1 Classroom Contact #19 "More Power To You"
Learning Objectives
Students will be able to:
Materials
For students:
To make the generator:
Vocabulary:


Part I:

Pre-Viewing Activities
Faraday's Induction
The teacher will set up the twin coil swings to demonstrate how electricity is created in a wire by moving a magnet. Thrust one magnet back and forth through the first loop. Ask the students to explain what makes the coils swing, and allow them one or two minutes to write an answer to this question. Tell them to be prepared to share their answer with the class.

TEACHER: Let's examine what you think makes the coils swing. A man by the name of Michael Faraday was the first to try to answer this question. In 1832, he said that electricity is generated in a wire whenever a magnet passes it. His ingenious idea became Faraday's Induction Law, but it was really by accident that he made this discovery. Michael did not go to high school. Instead he was trained as a bookbinder, starting at the age of 14, for 8 years, then became a lab assistant in a large university. Most of the time he was trying to convert magnetism to electricity. In the lesson today, we will explore this relationship between electricity and magnetism -- the E and M connection -- and then we'll build a generator. Later on, we will use some power sources, such as a battery, to turn over a motor of your own creation! OBJECTIVE 1.

TEACHER: (The teacher points to the demonstration.) The first loop is an electric generator like the one Faraday made in 1832. It converts mechanical power to electrical power. The second loop is a motor, and it converts electricity to mechanical power, such as in a car motor. We need to learn the difference between these two machines.
Focus Viewing
It is very important to give students a focus for viewing. This helps them focus their attention on the lesson objectives. This way students learn that the video is not solely for their entertainment.

TEACHER: Let's watch a video showing cast member Stephanie making electricity, using her personal, home-made generator. Later on, she will show us different power sources we can use to run our generators and motors.
Viewing Activities
Generating Electricity
TEACHER: How can I make electricity? Watch the video now and be able to explain how electricity is created.

START video on the title "More Power To You."
PAUSE video after you hear, "Didn't I tell you it was simple."

TEACHER: List two different ways to make electricity. (You make electricity by moving a magnet past a wire. Or, by moving a wire past a magnet. It doesn't matter which one moves. The ignorant wire can't tell the difference!) Ask a student to demonstrate the generation of electricity with a wire and a magnet. We are observing Faraday's discovery of making electricity using magnets. Why isn't it practical to make electricity this way? Watch the video carefully to learn why not? OBJECTIVE 2.

RESUME video.
PAUSE video after you hear the sentences: "You need a steady flow of electricity. You need a generator."

TEACHER: Why isn't it practical? (Electricity comes in spurts. The lights in your house would go on and off, on and off.... That's very annoying!) What do you need to make a steady flow of electricity? (A generator.) Scientists call this flow of electricity "current." Write "current" on the chalkboard. Ask a student to recite the definition. To see how a generator produces a steady current, observe Stephanie in the video as she shows you how a generator works to produce a steady current.

RESUME video.

STOP video after you hear the words, "After a while your arm gets really tired."

TEACHER: What happens when the loops of wire turn inside the magnet? (It makes a steady current of electricity, according to Faraday's famous law.) Scientists have a fancy word for loops of wire -- they call it a coil. (Write the word "coil" on the chalkboard.) Where does the current of electricity go from the coil? (Through the wires and then into the light bulb, which lights up!) What does Stephanie use to turn the wire inside the magnet? (Kid power -- she used her own muscle power.) Did she produce a steady flow of electricity? (Yes.) How much electricity? (Enough to light up the little bulb.)
Post-Viewing Activities
Building an E-M Generator
TEACHER: Let's use Faraday's law of making electricity, and make a toy generator. You will need the following materials: a coil of wire, a bar magnet, a 4-inch steel nail, a plastic straw, and a neon lamp. Your challenge is to construct a generator from these materials and make enough electricity to turn on a small neon lamp. Do the following: Make about 50 turns of bare wire around a straw to make a coil. Insert a steel nail through the coil. Connect the leads of the coil to the neon lamp. Then, stroke the magnet back and forth across the coil. When the neon lamp glows, you have made electricity from an "electromagnetic generator," or E-M generator for short. How else can we make electricity? (According to Faraday's induction law, you can also move a wire past a magnet.) Allow students 10-15 minutes to construct their generators. Display them around the classroom for everyone to observe. Construct a large banner with Faraday's famous Induction Law: "Electricity is generated in a wire whenever a magnet moves past it." OBJECTIVE 3 & 4.

Part II:

Pre-Viewing Activities
Power Sources: Here comes the Sun!
TEACHER: Think about why your generator is not practical. (Because it does not make enough electricity to run the lights in your home or your TV set. And, after a while your arm gets really tired from turning the generator.) So, what do we use to make all of the electricity we use everyday? (A bigger generator!) Instead of kid power, what do we use? Let's make a class list of what we can use. (Water power, steam power, solar power. Ask a student to go to the chalkboard and start to prepare the list with the help of the whole class.) Scientists have a word for all of these things, such as kid power, which are able to turn or do work on the generator. They call them power sources. (Write "power sources" at the top of the list and define it.)
Viewing Activities
Touring Electric Power Plants
TEACHER: Let's go back to the video to check our list of power sources. We will be going on an electronic field trip to Las Vegas to check out one of the world's largest power stations.

START video as Stephanie says, "So, what do we use to make all of the electricity we use every day?"
PAUSE video after you hear the words, "So what keeps the lights on in Las Vegas? Water power from Hoover Dam, that's what," with a picture of Hoover Dam.

TEACHER: What turns the generator -- spins the coil of wire inside the magnet? (Running water -- water power! Point to "water power" on the class list.) What name is given to the wheel-like machine that turns the shaft inside the generator? (A turbine. Point to the needle (the shaft) in the toy generator.) How can we make more electricity for Las Vegas? (Increase the water flow at Hoover Dam. That turns the turbine faster and makes more electricity.)

REWIND video to the start of the animated sequence.

TEACHER: Let's observe again how water power works. Listen carefully this time for the different parts of the water powered generator.

RESUME video.
PAUSE just after you hear Stephanie explain how water power works.

TEACHER: You are to draw a picture on a sheet of paper showing how electricity is made from water power. Label the turbine, the shaft, and the generator. Ask a volunteer to draw the water-powered electricity-making machine on the chalkboard. Although Faraday's discovery was at first taken with a grain of salt, today all our electric power is generated by moving giant coils of wire near magnets. It is amazing that just by our connecting copper wire and steel magnets in a power plant, falling water can rotate turbines which make enough electricity to light up all of Las Vegas and other big cities many miles away! What can you use for wind power? (A windmill.) Let's observe Miguel, Stephanie's assistant in the field, as he explains how wind can make electricity -- down on the "wind farm" in California.

RESUME video.
PAUSE video at the end of the electronic field trip.

TEACHER: How can wind make electricity? (The wind turns the blades of the windmill, known as the turbine, which in turns spins the shaft that turns the coil inside the magnet, known as the generator, and it produces the electricity.) Draw a second picture on a sheet of paper that shows the parts of the wind-powered electricity-making machine. So, wind can make electricity, and water can make electricity. How can steam make electricity? Set up an experiment to show that steam can be produced from different fuels, such as lamp oil, natural gas, and alcohol. Let's watch the video to observe how oil power works.

RESUME video.
PAUSE video at the end of the field trip to the oil power plant.

TEACHER: How does oil make electricity? (Oil is burned to heat water which makes steam. Steam moves the turbine blades that turn a shaft inside the generator. The shaft spins the coil of wire inside a magnet in the generator that produces a current of electricity.) After the electricity is produced, where does it go from there? (It goes up to the high tension wires. Draw a third picture that shows how electricity is made from burning oil. Allow students 1 or 2 minutes to complete their drawing.) There's more than one way to boil water to make steam. Instead of oil, what other fuels did we say you can use to make electricity? (Natural gas, coal.)

TEACHER: These fuels are called "fossil fuels" because they come from dead plants or animals that were buried in the ground and became fossils. Scientists call fossil fuels "buried sunshine" because plants make their food or fuel from the sun's power, then die and get buried. Which fuel is buried sunshine -- sunflower oil or motor oil? (Motor oil, because it comes from buried plants or animals.) Like sunflower oil, motor oil is really sun oil. Instead of using buried sunshine or "sun oil," we are going to find out how we can use the sun itself to make electricity. Let's take a field trip to the Solar I Power Station in California with fieldguide Miguel. Be able to tell me what Miguel has to say about sun power (solar power).

RESUME video.
PAUSE video at the end of the electronic field trip.

TEACHER: How does sun power make electricity? (Large mirrors reflect sunlight and focus it to heat water in a receiver. Steam made by the heated water flows through pipes under pressure to the turbine and turns its blades. The turbine is attached to the turning shaft that goes into the generator, and that's where the electricity is produced.) Take two minutes to draw a picture that shows the parts of the sun power station. We'll then watch the video to review what we have learned so far.

RESUME video.

STOP video at the end.

TEACHER: So, let's review. How can you make electricity with a magnet and a wire? (Move a wire past a magnet or a magnet past a wire. This is Faraday's Induction!) How can you make a steady flow of electricity? (By spinning a coil inside a magnet. The two parts make up a generator.) What are some power sources used to run a generator? (Running water, steam, fossil fuel, the sun.) List the steps in making electricity from a power source. (For example, wind turns the turbine that rotates a shaft inside the generator where the electricity is made by a coil spinning inside a magnet.) Check the class list of power sources. Did we miss one? OBJECTIVE 5 & 6.
Post-Viewing Activities
The Clean, Green Machine
TEACHER: Let's identify clean power sources for making electricity. From the class list, give me examples of clean power sources? (The sun, wind, or water.) Why is oil not a clean source of power? Burn the kerosene lamp oil for students to observe the smoke. (It makes air pollution.) Is a battery a clean power source? (Yes, it is a power source, since it can be used to make electricity. If it does not contain toxic chemicals, then it is a clean or nonpolluting source. A battery is really a "chemical generator.") What about a solar cell? (Yes, it makes electricity without polluting the environment. It's a clean, green machine!)

TEACHER: Can we use our clean, chemical generator -- the battery -- to make a motor? The worksheet titled "The Green Machine" [located at end of lesson] shows you how to build and operate a motor. Use this diagram to build the motor and make it work.

Teacher circulates among the students to assist them in building the motor. Allow students to experiment with a second magnet to see if they can change the speed of the motor. Ask them to try placing a pair of attracting magnets on top of the battery, in place of the single magnet. Allow students 15 minutes to build their motors.

TEACHER: Compare your toy motors and generators. List the differences between the two. (It is suggested that the teacher make a Venn diagram to show the comparison. Generators make electricity, but motors produce motion or mechanical power. Also, generators use a power source to move a turbine or mechanical power that is converted to electricity. Electric motors are the opposite: they use electricity as a power source, such as batteries.) So, as you can see, a motor is really a generator running "backwards"! Now, use your knowledge of electricity and magnetism to explain what makes the twin coils swing? If you understand the E and M connection, you can see what turns on the generator and the motor. Power is being converted back and forth from electricity (E) to magnetism (M). OBJECTIVE 7.

ASSESSMENT: Evaluate student learning by demonstrating the twin coil swings and asking students to write one paragraph explaining what makes the coils swing. Ask them to make a sketch of the twin coil swings and label the following: motor, generator. Allow them one or two minutes to write an answer to this question.
Action Plan
  • Arrange a field trip to an electric generating station. Assign homework for each student to prepare at least five questions about electricity to ask the tour guide during the visit.

  • Arrange a field trip to an electrical company. Inquire about careers in electricity.
  • Extensions
    History and Science:
    1. Research the English scientist Michael Faraday. Write a report on his life as a boy and the events that led him to become a great scientist and inventor.
    2. Research the variety of motors that were built since the eighteen hundreds. Compare the power output of gasoline motors with electric motors.

    Art and Science:
    Design and construct a chemical generator -- a battery. Test the battery using a small bulb lamp.

    Math and Science:
    1. Students measure the current and voltage produced by their toy generators. Compile the data as a whole class, and compute the average and the range of the data. Compare their values to that of commercial electric generators.
    2. Students construct two toy electric motors, using one and two magnets. Compare the voltage and speed of the motors. Graph the results.

    Careers in Science, Math, and Technology:
    1. Research careers in electricity and electronics.
    2. View other ASSET courses on careers in science, such as Futures and Futures2, Discovering Women in Science, and BreakThrough, Interactions: Real Science Real Math, #4, "Solar Power."

    Laserdisc:
    Electricity, Chapter A16, "Electric Forces and Fields." Seattle, Washington: Videodiscovery, Inc., 1992.

    CD Rom/Computer Software:
    Time Shift Radio, Tom Snyder Productions, 1995.
    Worksheet
    Click here to view the worksheet associated with this lesson.

    Master Teacher: Steve Martin

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