Hands-on Activity: Light vs. Heat Bulbs

Contributed by: Office of Educational Partnerships, Clarkson University, Potsdam, NY

Cartoon drawing of an incandescent light bulb next to a photo of a CFL
Students explore the efficiency of light bulbs
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Students measure the light output and temperature (as a measure of heat output) for three types of light bulbs to identify why some light bulbs are more efficient (more light with less energy) than others.

Engineering Connection

Substituting energy-efficient light bulbs is one way to reduce energy consumption. Lighting needs are still provided, but with less energy use. Engineers are developing many new types of light bulbs. CFLs are becoming commonplace, but we can expect new and improved ones soon.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

  • Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description--providing causes for effects and establishing relationships based on evidence and logical argument. This standard requires a subject matter knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Think critically and logically to make the relationships between evidence and explanations. Thinking critically about evidence includes deciding what evidence should be used and accounting for anomalous data. Specifically, students should be able to review data from a simple experiment, summarize the data, and form a logical argument about the cause-and-effect relationships in the experiment. Students should begin to state some explanations in terms of the relationship between two or more variables. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Communicate scientific procedures and explanations. With practice, students should become competent at communicating experimental methods, following instructions, describing observations, summarizing the results of other groups, and telling other students about investigations and explanations. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Use mathematics in all aspects of scientific inquiry. Mathematics is essential to asking and answering questions about the natural world. Mathematics can be used to ask questions; to gather, organize, and present data; and to structure convincing explanations. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Mathematics is important in all aspects of scientific inquiry. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Electrical circuits provide a means of transferring electrical energy when heat, light, sound, and chemical changes are produced. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Science influences society through its knowledge and world view. Scientific knowledge and the procedures used by scientists influence the way many individuals in society think about themselves, others, and the environment. The effect of science on society is neither entirely beneficial nor entirely detrimental. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
  • Technology influences society through its products and processes. Technology influences the quality of life and the ways people act and interact. Technological changes are often accompanied by social, political, and economic changes that can be beneficial or detrimental to individuals and to society. Social needs, attitudes, and values influence the direction of technological development. (Grades 5 - 8) Details... View more aligned curriculum... Give feedback on this alignment...
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Learning Objectives

After this activity, students should be able to:

  • Calculate energy use and analyze how changing their behaviors and appliances impacts the amount of energy they use.
  • Conduct an experiment and make comparisons based on experimental evidence.

Materials List

Each group needs:

  • incandescent light bulb (60 watt) with light socket/plug
  • compact fluorescent light bulb (CFL, 13 watt) with light socket/plug
  • LED bulb with light socket/plug
  • infrared (IR) thermometer (available at Radio Shack or similar stores)
  • ruler
  • Student Worksheet, one per student
  • (optional) watt meter, to confirm power

To share with the entire class:

  • light meter


Lighting accounts for 20-25% of all the electricity used in the U.S. On average, a household uses 5-10% of its energy for lighting. A commercial industry, on the other hand, consumes 20-30% of its energy in lighting only; 50% or more of the energy used is wasted by obsolete equipment, inadequate maintenance, or inefficient use. Energy savings for lighting will require either reduction in use or more efficient usage.

Recall the differences – conservation = turning off light bulbs, efficiency = using bulbs to produce light with less electricity). Today's activity focuses on efficiency.

Note that new technologies (developed by scientists and engineers!!!) can bring about substantial savings in energy use but still provide us with the benefits of electrical lighting. (Hold up various types of bulbs.) Do these look familiar? (Expect students to be familiar with incandescent and [hopefully] CFLs, but they may not have seen LED [light-emitting diode] bulbs.) LEDs are currently quite expensive, but we should see more of them in stores in the coming years.


  1. Divide the class into groups of three or four students each.
  2. Hand out the activity sheets and go over the procedure. (5 min)
  • Provide the lux reading for each bulb.
  • For Part II, it is better to work as a class or in very small groups (1-2 students). This can be started as they wait for the light bulbs to heat up.
  • As a demo or extra station, introduce LED bulbs (light-emitting diode).
  1. Complete the data collection. Note: it is important that several readings of temperature be taken for each bulb from sides and top as significant variations in the temperature exist around the bulb. Have students choose a representative temperature, the maximum, or take several readings and calculate an average.
  2. Discuss reasons for increased efficiency – light – the desired energy "product", but also varying amounts of heat generated. . Remind students that in some cases heat is the desired product, such as waming lamps for food, or for incubation. However, light bulbs would ideally produce no heat. Also ask if this is possible? (Answer: No, entropy is always increased, there is no such thing as 100% efficiency)."
    A cartoon drawing of a light bulb with electricity flowing in and heat and light flowing out
    In a light bulb, electromagnetic energy (electricity) is converted into heat and light, which is also an electromagnetic form of energy.
  1. Review conservation and efficiency ideas (perhaps using the classroom board) and spend a minute or two talking about the final project. Tell the class that they will need to define their ideas. Which applications suit the incandescent bulbs better? And which suit the CFL/LED bulbs better? Does it make sense in some instances to want both heat and light produced?


Safety Issues

  • The bulbs can get quite hot, especially the incandescent bulb, so warn students to not touch the bulbs.
  • Warn students not to look at the bulbs for too long; they might strain their eyes.


Worksheets: Collect and review student worksheet to assess their data collection, calculations and answers to discussion questions.

Other Related Information

This activity was originally published by the Clarkson University K-12 Project Based Learning Partnership Program and may be accessed at http://www.clarkson.edu/highschool/k12/project/energysystems.html.


Jan DeWaters; Susan Powers; and a number of Clarkson and St. Lawrence University students in the K-12 Project Based Learning Partnership Program


© 2013 by Regents of the University of Colorado; original © 2008 Clarkson University

Supporting Program

Office of Educational Partnerships, Clarkson University, Potsdam, NY


This activity was developed under National Science Foundation grant nos. DUE 0428127 and DGE 0338216. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.