Investigating Lightbulbs

6, 7, 8

Through a scientific investigation, the students compare features and costs of two types of lightbulbs. This lesson helps the learners understand how energy efficiency choices can impact their family energy costs and reduce the amount of energy consumed.

PrintTwo 50-Minute Class Periods

The learner will:

  • complete a lab activity comparing two lightbulbs.
  • compare the appearance, cost, and brightness of incandescent and compact fluorescent lightbulbs.
  • calculate the costs of each type of lightbulb (cost to buy and cost to use).
  • define stewardship as the careful and responsible management of something entrusted to one's care.
  • brainstorm the environmental benefits of using one type of lightbulb.
  • discuss ways to encourage others to use one type of lightbulb.
  • Newspaper headlines related to the price of electricity (see Teacher Preparation)
  • Student copies of Handout One, Lights Light Up Your Life Data Sheet
  • Graph paper
  • Each lab group (or one per class for a demonstration) needs the following supplies:
  • Calculator
  • Light meter (if available)
  • Two thermometers (room or lab/see this website for example)
  • Compact fluorescent lightbulb with power rating (Watts) stamped on the side
  • Incandescent lightbulb with power rating (Watts) stamped on the top
  • Two standard sockets or lamps
  • Tape measure, yard stick, or meter stick
Teacher Preparation 
  • Rather than obtaining supplies for each lab group, you may set up the light demonstration in a central location for groups to observe. Or set up stations for different observations.
  • Before the students arrive, access online newspaper websites to download recent headlines and lead sentences about the price of electricity. Type "electricity cost" into the newspaper search field. Print (or read aloud) three or four recent headlines for students to read and discuss.
  • Save the packaging and price tags from the lightbulbs so students can compare the costs to purchase each type of lightbulb. The packaging also includes lumens (light output) and the life expectancy (number of hours it will last).
  • If possible, contact the electric company (or look at an electric bill) to find out the cost of electricity per kilowatt-hour. If you are unable to obtain the price, the worksheet contains a price per kilowatt-hour for an equation (but it won't be a current price).


  1. Anticipatory Set:

    As students enter the room, they read several newspaper headlines/lead sentences posted on the classroom wall related to electricity. (See Teacher Preparation above.) Discuss the relevance of the headlines. What is the global concern related to electricity? Relate this topic to the students tracking electricity usage for the past week.

  2. Show learners one incandescent lightbulb and one compact florescent lightbulb (CFL). Ask the learners to describe the difference between the two lightbulbs. Allow learners time to share their answers and discuss the appearances (and their prior knowledge) of the two lightbulbs. On the board, write the prices per package and the number of bulbs in each package. Ask the students to calculate the price per lightbulb. Look at other features and claims on the packaging. Tell the students that today they are going to investigate the real costs of using these two types of lightbulbs.

  3. Remind the students that in the previous lesson they discussed the concepts of conserving energy and stewardship. Tell them that in order to conserve energy and reduce waste, they should promote the use the most efficient lightbulbs in their houses and other buildings at school and in the community. Tell them that the Energy Star group claims the CFL is ten times more efficient than the incandescent lightbulb. But we should use science to prove that to ourselves before we commit to spending more money per lightbulb.

  4. Distribute Handout One: Lights Light Up Your Life Data Sheet to each student. They will use this lab sheet to step-by-step compare and contrast several features of these two lightbulbs. Ask each learner to make predictions about the lightbulbs in the prediction section of the worksheet.

  5. Arrange learners into groups (groups of four learners works the best for this investigation).Distribute the materials for each group: two light sockets, one incandescent bulb, one compact fluorescent bulb, two room thermometers, one light meter, and a meter stick. If you choose to do this as a demonstration (and reduce the number of supplies needed), set up the lights where all groups can see them. Representatives from each group may go to the demonstration area, as needed, to collect data and then return to their lab groups.

  6. Tell the learners to carefully read and follow the instructions on the lab sheet to do the investigation.

  7. Allow a reasonable amount of time for the learners to do the investigation. Ask each group to choose a representative to report the group's conclusions.

  8. Bring the class back together and discuss the results of the lab. Ask each group's representative to report their findings and conclusions. The groups should have found that the compact florescent lightbulb costs less to operate and generates less heat, thus saving energy while producing equivalent light. (If you do not have a light meter, compare the brightness of the bulbs using the information on the packaging.)

  9. Ask the students how they, as consumers, can use this information. Discuss the cost, impact on the environment, and other efficiencies. Help students articulate the idea that by using less energy when lighting their homes they are helping to conserve resources. Make sure they understand that energy conservation is important because electricity is often produced by non-renewable and polluting fossil fuels (coal and oil). Guide them to recognize that it is also the responsibility of each citizen to be good stewards of resources. Using more efficient lighting is one way to conserve energy.

  10. Encourage the students to think of ways they can be advocates for using CFLs. They may recognize that the cost of the CFLs will be prohibitive to some families, but the cost savings in the long run will help them. Would teaching other people in the community about the lightbulbs help the whole community and themselves? Discuss opportunities for raising awareness or assessing needs. (This may become part of their final project at the end of lesson three.)


Assess the learners’ group participation. Collect the completed Handout One: Lights Light Up Your Life Data Sheets and assess these for completeness.

Philanthropy Framework

  1. Strand PHIL.I Definitions of Philanthropy
    1. Standard DP 01. Define Philanthropy
      1. Benchmark MS.4 Give examples of how individuals have helped others.
  2. Strand PHIL.II Philanthropy and Civil Society
    1. Standard PCS 03. Philanthropy and Economics
      1. Benchmark MS.5 Define <i>stewardship</i> as a trust of common resources held by a community for citizens.
      2. Benchmark MS.7 Give examples of common resources in the community.
    2. Standard PCS 07. Skills of Civic Engagement
      1. Benchmark MS.4 Analyze information to differentiate fact from opinion based on the investigation of issues related to the common good.
  3. Strand PHIL.IV Volunteering and Service
    1. Standard VS 01. Needs Assessment
      1. Benchmark MS.1 Identify a need in the school, local community, state, nation, or world.
      2. Benchmark MS.2 Research the need in the school, neighborhood, local community, state, nation, or world.