Materials

• Wire, (insulated copper wire with plastic coating, apx. 6 inches long with copper ends exposed), 2 per student
• "D" cell batteries, 1 per student
• Flashlight Bulbs, 1 per student (have a few extra bulbs on hand in case one is dropped)
• Simple Circuits: What Works? sheet, 1 per student

Prep Step

• Review the lesson plan, background information, and understanding goals.
• Gather batteries, bulbs and wire.
• Test all bulbs and batteries to ensure that they are working properly.
• Photocopy the sheet, Simple Circuits: What Works?.

Analyze Thinking

Step 1: Considering Initial Models

Explain to the students that they will be learning about how simple electrical circuits work. As a safety precaution, stress that while this unit will help them understand some things about the electricity in their homes, they should never experiment with electricity at home. It is very dangerous to do so. The batteries used in class have a voltage that is low so that the students will not be hurt. This is not true of the electricity in their homes.

Show the students a battery, a bulb, and one wire. Ask them to think about what they would do if they wanted to light the bulb using the wire and the battery. Ask them to draw a diagram on paper or in their journals, and under their diagram to explain why it would work. As students are working, circulate to see what kinds of models they are drawing. Most students typically draw a Simple Linear Model as outlined in the introduction.

RECAST Thinking

Step 2: Discovering That Linear Configurations Don't Work

Pass out the Simple Circuits: What Works? sheet, a battery, a bulb, and one wire to each student (the second wire will be passed out later in the lesson). Explain to your students that their challenge is to try to light the bulb using just the materials that you have given them. Make sure that students record ALL of the configurations that they try, even those that don't work. Finding patterns in what doesn't work is as important as finding patterns in what does work for developing a good explanatory model. Explain that it might take them a while to find ways that work. That is fine. The idea is to explore possible configurations until they find some that do work.

Circulate while students are working. Ask:

• Why do they think different arrangements are working? What do they think is going on? (Tell your students that there are at least four configurations that work to light the bulb.)

After students have successfully figured out how to light the bulb with a battery and one wire in four different ways, give them a second wire and see if they can apply what they have learned to lighting the bulb using two wires instead of one. Surprisingly, some students are initially uncertain about how to use two wires and grappling with the second wire reinforces what it is about the configurations that work. Afterwards, students may continue to experiment. Encourage this experimentation by offering additional wires, bulbs, and batteries. Ask students to predict whether certain arrangements work and what they found out when they tried them.

Explore Causality

Step 3: Revising Initial Models

Have students consider the following questions:

• What similarities are there between the arrangements that work?
• What differences are there between those that work and those that don't?
• What do you think is going on at the atomic level (electrons, protons, and neutrons) when the bulb lights?

Have students revise the models that they drew at the beginning of the class. After they have drawn one model, have them create a rival model by drawing a second diagram that is different from their first diagram, but that also could explain what is going on.

Review, Extend, Apply

Step 4: Making Connections