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How do light bulbs work?

Pam Fier-Hansen, Marshall High School, Marshall, MN 56258
Activity based on a CASTLE electricity Activity and Physics by Inquiry (McDermott). The teacher demo was done by Eric Koser during the MnSteps physics workshop.
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Summary

This is a guided inquiry that involves observation of the parts of a light bulb in a lab. It would be nice if students also had access to the internet during this time. As an alternative, printed copies of the information from the internet could be given to the students.

Learning Goals

Goals
1. Students will understand the flow of eletricity through a lightbulb.
2. Students will understand the role of each of the parts of a lightbulb.
3. Students will compare the efficiency of a standard light bulb and a high efficiency compact fluorescent bulb.
Skills:
Students will observe the parts of a lightbulb and predict the role of each part of the bulb. They will gather information from web sites and explain the role of each part in writing.
Key concepts
Students will detrmine how electricity flows through a lightbulb.
Students will compare the cost of using a standard light bulb and a high efficiency bulb.
Vocabulary:
filament
watt
kilowatt/hr

Context for Use

This will be used in my general physics course (grades 10-12) as an additional activity in our unit on electricity. It could be easily adapted to a physical science level.
The only equipment required is a lightbulb in which the glass has been removed and an electricial socket that the bulb fits into. Students should have some understanding of circuits, conductors, and insulators before this activity is introduced. I think that it will take about 30 minutes for the students to complete the activity, watch teacher demonstration, and gather information from the web sites.

Subject: Physics:Electricity & Magnetism
Resource Type: Activities:Lab Activity, Classroom Activity
Grade Level: High School (9-12)

Description and Teaching Materials

I will use this acticity as an addition to my unit on electricity. In this unit, students detemine the conducting path in a light bulb. This activity is designed to expand what the students learn about how a light bulb works. The students will have completed the activity on making a light bulb light with a D cell battery and one wire. From this activity, they should be aware of what parts of the light bulb must be part of a conducting path. In this activity, students will observe a light bulb in which the glass has been removed. They should note the location of wires within the bulb, and compare the diameter of the filament to that of the supports. Finally, they will compare the cost of using a standard light bulb to a compact fluorescent bub. Student handout (Microsoft Word 37kB Aug24 07) Useful web sites (Microsoft Word 24kB Aug24 07)

Teaching Notes and Tips

Care should be taken when removing the bulb from the light bulb. Students should handle it carefully. In the teacher demo section, when the socket is plugged in, the tungsten filament will burn quickly and brightly. This is due to the fact that the metal oxidizes rapidly at the high tempertures in the filament.
In the past, I have only had students determine the path of electricity in a bulb.

Assessment

Students will write down their observations and explanations on the attached student handout.

Standards

Grade 9-12 II.C.4-Energy transformations

References and Resources

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