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Seeing the Light: The Physics and Materials Science of the Incandescent Light Bulb
© GA Sciences Education Foundation 1996-2002, All Rights Reserved
1
Seeing the Light:
The Physics and Materials Science of the Incandescent Light
Bulb
February 20, 2002
Dr. Lawrence D. Woolf
General Atomics
San Diego, CA 92121
Larry.Woolf@gat.com © GA Sciences Education Foundation 1996-2002, All Rights Reserved
2
Table of Contents
Section

Page
Table of Contents ------------------------------------------------------- 2
Correspondence to the National Science Education Standards ---
3
Correspondence to the Benchmarks for Science Literacy ----------
5
Logical Construction of Module --------------------------------------- 8
Introduction and Basic Physics --------------------------------------- 9
Introduction to Filament Design Parameters ------------------------
12
Experiment 1: The Room Temperature Filament --------------------
14
Resistance of Different Wattage Light Bulbs
Experiment 2: The Temperature Dependence of the ----------------
17
Resistance of a 100 W Light Bulb
Experiment 3: The Electrical Properties of 3-Way Bulbs -----------
19
Experiment 4: Light Bulb Design ------------------------------------- 24
Experiment 5: Light Bulb Dissection -------------------------------- 26
Experiment 6: Light Bulb Fabrication ------------------------------- 28
Advanced Topic: Oxidation Resistant Materials ---------------------
30
Advanced Topic: Blackbody Radiation -------------------------------- 32
Advanced Topic: Filament Material -----------------------------------
33
Advanced Topic: Filament Environment -----------------------------
35
Advanced Topic: Microscopic View of Incandescence --------------- 36
Advanced Topic: A Brief History: The Edisonian Approach -------- 37
Problems -----------------------------------------------------------------
38
Solutions ----------------------------------------------------------------
39
References ---------------------------------------------------------------
44
Materials Required -----------------------------------------------------
45 © GA Sciences Education Foundation 1996-2002, All Rights Reserved
3
Correspondence to the National Science Education Standards
(NSES)
This unit relates to the following NSES physical science content standards in grades 5-
8:
Properties and Changes of Properties in Matter
A substance has characteristic properties, such as density, a boiling point, and
solubility, all of which are independent of the amount of sample.
Substances react chemically in characteristic ways with other substances to form new
substances (compounds) with different characteristic properties.
Electrical circuits provide a means of transferring electrical energy when heat, light,
sound, and chemical changes are produced.
Transfer of Energy
Energy is a property of many substances and is associated with heat, light, electricity,
mechanical motion, sound, nuclei, and the nature of the chemical. Energy is transferred
in many ways.
Heat moves in predictable ways, flowing from warmer objects to cooler ones, until
both reach the same temperature.
Electrical circuits provide a means of transferring electrical energy when heat, light,
sound, and chemical changes are produced. © GA Sciences Education Foundation 1996-2002, All Rights Reserved
4


This unit relates to the following NSES physical science content standards in grades 9-12:


Conservation of Energy and the Increase in Disorder

The total energy of the universe is constant. Energy can be transferred by collisions
in chemical and nuclear reactions, by light waves and other radiation, and in many other
ways. However, it can never be destroyed.
Heat consists of random motion and the vibrations of atoms, molecules, and ions. The
higher the temperature, the greater the atomic or molecular motion.
Everything tends to become less organized and less orderly over time. Thus, in all
energy transfers, the overall effect is that the energy is spread out uniformly. Examples
are the transfer of energy from hotter to cooler objects by conduction, radiation, or
convection and the warming of our surroundings when we burn fuels.


Interaction of Energy and Matter

In some materials, such as metals, electrons flow easily, whereas in insulating materials
such as glass they can hardly flow at all. © GA Sciences Education Foundation 1996-2002, All Rights Reserved
5
Correspondence to the Benchmarks for Science Literacy
4E Energy Transformations
8th grade
Energy cannot be created or destroyed, but only changed from one form to another.
Energy in the form of heat is almost always one of the products of an energy
transformation.
12th grade
Whenever the amount of energy in one place or form diminishes, the amount in other
places or forms increases by the same amount.
Transformations of energy usually produce some energy in the form of heat, which
spreads around by radiation or conduction into cooler places.
4G Forces of Nature
12th grade
Different kinds of materials respond differently to electric forces. In conducting
materials such as metals, electric charges flow easily, whereas in insulating materials
such as glass, they can hardly move at all.
3C Issues in Technology
8th grade
Technology has strongly influenced the course of history and continues to do so. It is
largely responsible for the great revolutions in agriculture, manufacturing, sanitation and
medicine, warfare, transportation, information processing, and communications that have
radically changed how people live.
11A Systems
8th grade
Thinking about things as systems means looking for how every part relates to others.
The output from one part of a system (which can include material, energy, or
information) can become the input to other parts. Such feedback can serve to control
what goes on in the system as whole.
Any system is usually connected to other systems, both internally and externally. Thus
a system may be thought of as containing subsystems and as being a subsystem of a
larger system. © GA Sciences Education Foundation 1996-2002, All Rights Reserved
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12th grade
Understanding how things work and designing solutions to problems of almost any
kind can be facilitated by systems analysis. In defining a system, it is important to
specify its boundaries and subsystems, indicate its relation to other systems, and
identify what its input and output are expected to be.
1C The Scientific Enterprise
8th grade
No matter who does science and mathematics or invents things, or when or where they
do it, the knowledge and technology that result can eventually become available to
everyone in the world.
12th grade
Progress in science and invention depends heavily on what else is happening in society,
and history often depends on scientific and technological developments.
Science disciplines differ from one another in what is studied, techniques used, and
outcomes sought, but they share a common purpose and philosophy, and all are part of
the same scientific enterprise. Although each discipline provides a conceptual structure
for organizing and pursuing knowledge, many problems are studied by scientists using
information and skills from many disciplines. Disciplines do not have fixed boundaries,
and it happens that new scientific disciplines are being formed where existing ones meet
and that some subdisciplines spin off to become disciplines in their own right.
8B Materials and Manufacturing
8th grade
The choice of materials for a job depends on their properties and how they interact with
one another. Similarly, the usefulness of some manufactured parts of an object depends
on how well they fit together with other parts.
Manufacturing usually involves a series of steps, such as designing a product, obtaining
and preparing raw materials, processing the materials mechanical or chemically, and
assembling, testing, inspecting, and packaging. The sequence of these steps is also
often important.
Modern technology reduces manufacturing costs, produces more uniform products, and
creates new synthetic materials that can help reduce the depletion of some natural
resources. © GA Sciences Education Foundation 1996-2002, All Rights Reserved
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12th grade
Scientific research identifies new materials and new uses of known materials.
Manufacturing processes have been changed by improved tools and techniques based
on more thorough scientific understanding, increases in the forces that can be applied
and the temperatures that can be reached, and the availability of electronic controls that
make operations occur more rapidly and consistently.
Acknowledgement
I would like to thank Professor Harvey S. Leff of the Cal Poly Pomona physics department
for many helpful suggestions and comments. © GA Sciences Education Foundation 1996-2002, All Rights Reserved
8
Logical Construction of Module
Exp. 1: Investigate filament resistance
of single wattage light bulb
Exp. 2: Investigate temperature
dependence of filament resistance of
single wattage light bulb.
Exp. 3: Investigate electrical properties
of 3 way bulbs.
Investigate the 3
way bulb
Investigate the 3
way switch