In this lesson, students will be constructing a model of an incandescent light bulb using their circuit building materials. In order for students to build shared understanding about light bulbs, I begin this lesson by asking students to draw and label their own model of an incandescent bulb. As we draw and label our bulb, students are exposed to new content-area vocabulary and develop knowledge about the inner-workings of a bulb. An example of a labeled scientific bulb diagram is here.
Before allowing students to work independently, I model the process of creating a light bulb model. Doing so allows me to clarify the procedures on their lab worksheets and to highlight safety rules and helpful tips I have gathered through my past observations. I show students how to use clay to hold the wires and how to wind the nichrome wire around the ends of the wire to create a filament. A photo of my completed model can be found here.
I then give students the task of creating a model light bulb using bulb, battery, wires, clay, nichrome wire, and a battery holder. The students draw on their newly created knowledge of light bulb parts when constructing their model. After successfully connecting their circuit, their model light bulb will create heat and light energy on the nichrome wire. I ask students to record their observations and procedures on their make a filament lab worksheet. A video of students engaged in building a light bulb model can be found here.
In the modern age where many households use CFLs (compact florescent lights), incandescent bulbs may be an unfamiliar item for many students. I make sure to have several samples on display in my classroom so that students can see and interact with an incandescent bulb. I also try to provide connections to students' lives. Many students still have incandescent bulbs in their nightlights at home, so I be sure to point this out to all students.
After students have had time to build their model light bulb, I provide students with the opportunity to visit the work stations of all other groups in the class. It is common to see varying degrees of success in the models and to have some models not work at all. Allowing students to view each group's model allows them to see working models, to compare and contrast each model, and to determine the characteristics of successful models.
Next, I lead students in a discussion of the flow of electricity throughout the light bulb. I discuss with students the energy transformation that occurs as electrons flow over the nichrome wire. I encourage students to draw the path of electrons on the light bulb diagram they created at the start of the lesson.
To reinforce the students' new understanding about the movement of electricity in a light bulb model, I guide students as they create and record a definition for fluorescence, incandescence, transformation, and watt in their electricity glossary.