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Electric Circuits

Students model, build, and draw diagrams of electric circuits and test the conductivity of a variety of materials.

Overview

Electricity -- we depend on it every minute of every day. And yet to many of us, electricity seems a mysterious and even magical force. Before Ben Franklin did his famous and very dangerous kite flying experiment, electricity was thought to be a type of fire. In 1847, the year Thomas Edison was born, most people considered electricity to be some sort of dangerous fad. By the time Edison died in 1931, entire cities were powered by electricity.

Although it has been used as an energy source for over 100 years, many people don't understand the basic principles of electricity. In this lesson, students begin to develop an understanding of electrical current. First, they act out an electric circuit. Then they use critical thinking skills and deductive reasoning to create their own electric circuits using a few simple materials. Next, students watch video segments of the ZOOM cast members using electric circuits to make a door alarm and a steadiness tester. Finally, students test the conductivity of a variety of materials.

Objectives

• Model the flow of electrons in a circuit
• Build an actual electric circuit
• Draw diagrams of electric circuits
• Explain how to tell when the path of an electric circuit is complete
• Test the conductivity of a variety of materials

Suggested Time

• Three 60-minute blocks

Multimedia Resources

Use these resources to create a simple assessment or video-based assignment with the Lesson Builder tool on PBS LearningMedia.

Materials

• balls, books, or erasers for the "Act Out an Electric Circuit" activity
• *wire strippers
• *insulated wire
• *flashlight bulbs
• *fresh D-cell batteries
• various materials for testing conductivity (suggestions: cardboard, salt water, aluminum foil, plastic, steel wool, wood, rubber, fabric, wire coat hanger)

*can be purchased at a hardware or electronics supply store

Before the Lesson

• Each pair of students will need two pieces of insulated wire, a battery, a flashlight bulb, and tape. Cut the insulated wire into six-inch segments. Remove one-half inch of plastic insulation off the ends of each segment. To do this, you can use wire strippers or you can score the plastic insulation around the wire with sharp scissors and then carefully but firmly pull it off with your fingers.

Part I: Act Out an Electric Circuit

• What is electricity?
• What is electrical current?
• What is an electric circuit?

Have them draw examples of electricity and electric circuits in their lives.

2. Tell students that they cannot see electricity because electrons, the charged particles whose movement through a substance creates electricity, are too small to be seen even with a microscope. When electrons flow through certain substances (like copper wire), they form an electrical current. Electrical current provides energy to power all kinds of things, from video games to refrigerators to cars!

3. Act out an electric circuit, as follows: Ask students to join you in forming a circle. Tell students that you represent a battery and they represent a wire conductor. The circle represents a circuit. (Note: The word circuit comes from the Latin circuitus, which means "to go around.") Distribute an object -- like a ball, a book, or an eraser -- to each member of the circle, including yourself. Ideally, everyone should have the same object. Tell students that these objects represent electrons inside a wire conductor. Explain that a wire conductor is full of electrons.

Remind students that you are playing the part of the battery in this circuit, and explain that all batteries have a positive end, represented by your left hand, and a negative end, represented by your right hand. Pass your "electron" to the student on your right. The student receiving your electron should in turn pass the one he or she is holding to the right. Have students continue passing on electrons to the person to their right. Tell students that because electrons share the same negative charge, they repel one another, which keeps them moving along in the same direction. State again that the flow of electrons through a conductor is called electrical current.

4. Tell students that as long as the circle remains intact and the electrons continue to flow, their circuit is closed. To illustrate what happens when a circuit breaks, or opens, create a gap in the circle of students that is too wide across to pass electrons. The current will stop as a result.

Part II: Light a Bulb

5. Tell students that they are going to apply what they just learned about circuits to light a bulb. Divide the class into teams of two and distribute two lengths of wire (with the ends stripped), a flashlight bulb, a D-cell battery, and some tape to each team. Challenge students to use their critical thinking skills and trial and error to get their bulbs to light. Then have them draw a diagram of their circuit, making sure to include all its parts.

6. Have students report their findings. Ask:

• Did you get the bulb to light?
• In what order did you connect the parts?
• How did you know that electricity flowed?
• Can you trace the path of electrons in your circuit?
• What happened if the circuit was broken, that is, if there was a gap in the circuit?

7. Next, show students the following videos: Designing Electric Circuits: Door Alarm, Designing Electric Circuits: Steadiness Tester, and Experimenting with a Lemon Battery. Have students work in groups to diagram the circuit featured in one of the videos. Then have each group present their diagram to the class and explain how the electricity flowed through that particular circuit.

Part III: Explore Conductivity

8. Explain that substances through which electricity can travel easily are called conductors. Substances through which electricity has difficulty moving are called insulators. Then show students the Exploring Conductivity: Kid Circuits video. Ask them if the ZOOM cast members make good conductors. Tell students that the human body is not a very good conductor. Demonstrate by trying to light a bulb using your (dry) hand as part of the circuit. (The bulb does not light.) It is because of the remarkably low level of current needed by the digital clock in the video segment that the ZOOM kids' bodies are able to complete the circuit. Ask:

• Do you think the kids would be able to get a calculator to work?"
• What materials do you think might conduct electricity well?"

9. Challenge students to test the conductivity of a variety of materials, using the battery and bulb circuits they built in Part II. Have them begin by cutting one of the circuit wires in half and stripping the insulation off the two new ends. Then have students touch (or attach) both ends of the newly cut wire to various materials and record their results. (This is a great activity to do at home; students can simply carry the circuit with them from room to room, testing different objects.)

10. Ask students to create a class list of conductors and insulators on the board and categorize the objects by the materials they are made of: metal, glass, and so forth. Ask them to identify any patterns they see. Then introduce new materials to the list and ask students to predict whether each material is a conductor or an insulator. For example, if they found that tin foil and copper wire were good conductors, which do they think a paper clip would be?

Check for Understanding

Ask students to work in groups to act out a battery-bulb circuit and what happens when the light bulb burns out.

Related Resources to Check Out

• Lightning! QuickTime Video
This video explores the mysterious force of lightning.
• Electric Girl QuickTime Video
ZOOM guest, Anna, loves electricity. Watch her construct a homemade flashlight.

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