ELECTRONIC CIRCUITS

1. Find out what students already know about electricity. Ask:
• 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.
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.
SAFETY NOTE
Exploring electricity is safe as long as it is done with low-voltage batteries (such as D-cell) and under adult supervision. Tell students never to experiment with electricity from a wall outlet. Doing so can be fatal.
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.
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.)