Federal Laboratory Consortium
Northeast Regional STEM Project
Report
Lesson Plans are Included
Plasma Speaker Speaks Physics
Sophia Gershman
Watchung Hills Regional High School
108 Stirling Road
Warren, NJ 07059
sgershman@whrhs.org
908-647-4800
Charles Gentile
Plasma Physics Laboratory
MS41 C-Site E 343
PO Box 451Princeton, New Jersey
US08543-0451
cgentile@pppl.gov
Office: 609-243-2139
Federal Laboratory Consortium
Northeast Regional STEM Project
Report
This report follows the same format as the original proposal modifying the
components from future plans to achieved steps. Unmodified paragraphs are
in italics.
Plasma Speaker Speaks Physics
a. Project Description
The main purpose of this project is to adapt a plasma speaker device to
educational use. The teacher with the support of the PPPL mentor and staff
worked with an undergraduate student to construct a plasma speaker. The
teacher wrote a set of activities addressing the learning progression needed
to understand the operation of a plasma speaker. The activities (attached
below) address the principles of audio reproduction by mechanical means
and by using electrical discharges.
July:
 The speaker was ordered but the kit was finally received on July 15.
 Test of the speaker basic circuit was completed by July 20th.
 The circuit board operation was tested
 Work on the write up for the activities and demonstrations
Photo of the Plasma Speaker
constructed at PPPL, summer 2011
August:
 Designed an enclosure to optimize student involvement and safety. In this design, the Tesla coil is
positioned on the top level of a wooden structure and its audio input and power circuits are placed at
the bottom level (photo above). The improvement to the design includes an outside switch panel. It
allows the speaker to be turned on without getting too close to either the secondary coil at the top or
the circuit board. The audio circuit and the primary power are turned on separately as is the cooling
fan. The switch panel is also equipped with an overall line power fuse. The photo doesn’t show the
final product. The final product includes a Faraday cage not shown here since the copper mesh
wrapping the entire box obscured the camera view of the circuit.
 The laboratory experiments have been written and are attached to this report. The activities are
written so that they can be easily adapted to various teaching styles, levels, and lesson formats. The
suggested grade levels for the activities are indicated at the start of each activity. The directions are
worded so that they can be directed to students or teachers. The students are usually intended as the
audience and the tips and warnings for teachers are included in the form of “notes”. Lastly, all
activities are written in an open ended format to fit the current “inquiry based” learning model.
 Test the laboratory experiments have been tested.
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b. What is the Science, Technology, Engineering, or Math component of the project?
The speaker construction and operation involves electromagnetic phenomena, the physics of sound,
the construction and operation of electrical circuits, and electrical and electronic circuit
components. These themes and topics are a part of standard course work in Physics, Engineering,
and Digital Electronics high school courses. In addition, general science courses on the Middle
School level discuss electromagnetic phenomena in the atmosphere such as lightning. The plasma
speaker can easily make teaching many of these abstract topics more visual and more obvious. For
example, students who have seen the prototype speaker demonstrated were amazed at the sound
disappearing when the discharge is disturbed without making any other circuit changes. In more
detail the science, technology, engineering, and math components are as follows:
Science:
The science components include the principles of electrical circuits including transformer action
and signal modulation, electromagnetic fields and their effects on charged particles, particle
collisions, light emission, gas phenomena, sound emission and propagation, and many more. The
beauty of this device is in bringing all the rich concepts and principles together but also allowing
students to see clearly how these apply to various parts of the device and its operation.
The activities designed and included below teach the operation of speakers that use membrane
vibrations, examine the audible noise generated by electrical discharges, and use these
components to construct the understanding of the way sound is generated in a plasma speaker.
Additional activities and projects can be developed at a later time after the teacher gains
experience using the speaker in the classroom. These additional materials can be shared later
during the school year.
Engineering and Technology:
Electrical circuit layout, principles of electrical safety, and project management (if the device is
constructed as a long term project), are just a few of many skills and topics from the Engineering
curriculum involved in this project. In addition, all of the electrical components are discussed,
used, and studied in the engineering and technology classes. These include capacitors, inductors,
amplifiers, diodes, transistors, switches, transformers, filtering circuits, and many more.
The labs written and included with this report include signal analysis, oscilloscope operation, and
basic electrical calculations that are a part of engineering and technology education.
Mathematics:
The lessons attached below include graphing and interpretation of graphs. The students are
required to understand and estimate the frequency of the audio and electromagnetic signals,
calculate the period of the signal from its frequency and visa versa. Student working on the
project calculated the input power of the transformers, the cooling fan, and other devices, and
computed the necessary amperage of the input fuse.
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Northeast Regional STEM Project
c. How will the project support a component of one of the national STEM innovation
programs? (Educate to Innovate, AAAS’s Project 2061, or Innovation America)
This project advances many aspects of the STEM education initiatives such as promoting
scientific inquiry, stimulating students’ and teachers curiosity, attracting students to the study of
science, and providing students and their teachers with opportunities for creativity and
innovation. The activities designed as a result of this project address for example the AAAS
Project 2016 aspects of benchmarks # 3 (The Nature of Technology: A and B) and #4 (The
Physical Setting: D, E, G).
d. Describe the qualifications of the candidate
Sophia Gershman teaches Physics and Research at Watchung Hills Regional High School. She
holds an MS degree in Solid State Physics and Education from Latvian State University (1980)
and a PhD in Experimental Plasma Physics from Rutgers University (2008). S. Gershman has
designed various curricular materials for Middle and High School teachers on topics of Energy,
Electricity, Plasma Physics, etc. She wrote the curricula for two different levels of Physics
courses, an Integrated Science course, and a project based Experimental Research and Design
program.
2. The Federal Laboratory Mentor on the project is Dr. Charles Gentile
3. The Laboratory Point of Contact is the same as the mentor.
4. Budget:
Support for
the candidate,
S. Gershman:
The equivalent of 6 weeks
of work including: putting
together the actual device
and writing curricular
materials
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Northeast Regional STEM Project
1. Improved plasma speaker
2. Curricular materials for Middle School and High
School levels (approx., 1 lab and one demo on
each level) ; all materials will be freely available
online
$2,500
Plasma Speaker Kit from Eastern Voltage Research,
Inc.http://www.easternvoltageresearch.com/plasmaspe
aker.html
$350.00
Other incidental materials and tools:
$250.00
Plasma Speaker Activities
Goals and objectives:
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Provide activities that will help students to
Understand and explain complex phenomena
Combine the macroscopic and microscopic models to explain the production of sound by
mechanical membranes and an electrical discharge such as a spark
Compare and contrast the mechanism of sound production by a magnetically driven (mechanical)
speaker, lightning, and the plasma speaker.
Activity 1: Paper Plate Speaker
All levels: grades 5 – 12
Note: young students will need adult help winding the coil; the winding must be very neat with each turn
in full contact with the previous turn
Objective: Construct a magnetically driven speaker using a coil, a paper plate, and a strong
magnet.
Directions for making a paper plate speaker:
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Loosely wrap a small piece of an index card around a C or a D battery and use a small piece of
scotch tape or glue to hold the ends together forming a loosely fitting cylinder. Use gauge 28
magnetic wire and wrap it around the paper cylinder without removing it from the battery. Make
sure to make the wire turns very neat and close to each other but don’t make the coil too tight
around the battery. You have to be able to remove the coil from the battery. Make 80 – 100 very
close turns. Neatly secure the wire and leave both ends of the wire exposed for connections.
Make sure to clean off the insulation from the tips of both wires. Remove the coil from the
battery and hold it vertically.
Attach a paper plate to the top of the coil. Fold 4 strips of stiff paper into accordion type folds
and attach the four legs symmetrically to the bottom of the paper plate, close to the edge. Check
that the plate with the coil attached at the bottom center can gently bounce on its paper legs.
Connect the coil wire to an audio source, radio or an mp3 player.
Position a strong magnet in the center under the coil. Make sure that the magnet is stationary and
the coil with the plate can move freely above the magnet.
Observations of the paper plate speaker in action and guiding questions:
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Turn on the music; listen, look closely, and very lightly touch the side of the plate. Record what
you see, feel, and hear.
What produces the sound you hear?
Explain how the electrical signal is electromagnetically converted to the motion of the plate.
Explain how the sound is produced.
Is it easier to hear high pitch (high frequencies) or low pitch sound?
Listen to a song that uses high pitch vocals, flute, violin, or synthetic high pitch tones. Repeat
with a song that uses low pitch drums or bass. Compare and record your observations.
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Extension #1:
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Use a tone generator to investigate the fidelity of this speaker. Generate several low and high
frequencies. Listen to each using your regular speakers or headphones and then compare to the
same signal reproduced by your paper plate speaker. Record any observations you may have.
Extension #2: High school level and above:
Measurements:
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Connect your tone generator to an oscilloscope and record the waveform of the signal. If the
signal is produced by a computer program, the program will allow you to record the waveform or
the Fourier transform of the signal, that is the information about the generated frequency(ies).
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Run your speaker and record the same tone played by the speaker using a microphone connected
to an oscilloscope or a computer. If possible, perform the Fourier transform of the signal to
determine the frequencies produced by your speaker.
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Compare the frequency signatures for several tones. Suggest possible explanations for any
deviations of the signal produced by the speaker from the signal generated by the tone generator.
Activity 2: Tesla Coil
All Levels (grades 5 -12):
Note: Adults should handle the Tesla coil. Students should be observers in this activity.
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Use a hand-held Tesla coil for this activity.
Plug the coil into an outlet and adjust the frequency until a discharge appears between the tip of
the coil and any grounded conductor, a faucet for example. Listen and describe the sound you
hear.
Extension: High school level and above (grades 9 – 14):
Note: This section lends itself to a rich variety of extensions depending on the level of the students
and the available time. The time spent here can vary from 1 – 3 hours.
Measurements:
 Connect a microphone to an oscilloscope and record the audible signal produced by the
discharge emanating from the tip of the Tesla coil. Look at the signal on a ms scale (or kHz
range). Describe what you see. Record if possible. The oscilloscope will also pick up the
electromagnetic signal from the Tesla coil itself. This signal could be seen on a scale of 200 ns –
500 ns.
 If the oscilloscope has the Fourier transform function, use it to find the frequency signature of
the signal in the audible range as well as in the full range of the signal. Save if possible or record
the characteristics of the signal to compare to the electromagnetic signal from the Tesla coil
itself.
 Using an oscilloscope equipped with a high voltage probe to measure the electromagnetic signal
produced by the Tesla coil. Note: You need to have high voltage probes rated to 40-50 kV and an
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oscilloscope capable of MHz resolution (about 500 Mhz gives really good results) Connect the
high voltage probe to the tip of the Tesla coil and connect the ground of the probe to the physical
ground. Turn on the Tesla coil. The signal will be seen on a scale of 200 ns – 500 ns.
If the oscilloscope has the Fourier transform function, use it to find the frequency signature of
the signal in the audible range as well as in the full range of the signal. Save if possible or record
the characteristics of the signal to compare to the signal recorded using a microphone.
Writing in Science:
All levels:

Write a narrative comparison of the data from the microphone and the high voltage tip of the
Tesla coil.
Activity 3: Plasma Speaker
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The plasma speaker consists of solid state power supply driving the primary coil, an audio
modulation circuit that produces amplitude modulation of the output signal, and a secondary coil
that drives a corona discharge.
Directions:
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To turn on the plasma speaker, first turn on a fan to cool the transistors, then turn on the audio
circuit, and finally turn on the Tesla coil power circuit. You should see a visible “flame-like”
coronal discharge emanating from the wire loop.
Plug in your audio source (preferably a CD or a DVD player) into the input audio jack. Listen
and describe the music here. Try adjusting your audionvolume and make observations.
Guiding questions/observations:
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What makes the sound in the plasma speaker?
Note: do not allow students to handle the speaker, but ask them to suggest what you can do to prove
the source of sound
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Compare to the mechanisms suggested for the paper plate speaker and for the hand-held Tesla
coil. Use this comparison to explain the mechanism of sound production.
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Compare and contrast the actual audible sound produced by the plasma speaker with the sound
from the paper plate speaker.
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Is it easier to hear high pitch (high frequencies) or low pitch sound?

Listen to a song that uses high pitch vocals, flute, violin, or synthetic high pitch tones. Repeat
with a song that uses low pitch drums or bass. Compare and record your observations.
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Extension: High school level and above (grades 9 – 14):
Note: This section lends itself to a rich variety of extensions depending on the level of the students
and available time. The time spent here can vary from 1 – 3 hours.
Measurements:
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Use an oscilloscope to examine the input audio signal. Connect the oscilloscope probe directly to
the audio output of the CD or DVD player you use for the plasma speaker. Record and save the
waveform as it is generated by your audio device.
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If your oscilloscope or computer based device has the capability of performing the Furrier
transform, use this feature to examine the frequencies present in your selected signal.
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Connect a microphone to the oscilloscope and record the audio signal. Compare to the signal
recorded directly from the CD player.
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Connect your tone generator to an oscilloscope and record the waveform of the signal. If the
signal is produced by a computer program, the program will allow you to record the waveform or
the Fourier transform of the signal, that is the information about the generated frequency(ies).

Run your speaker and record the same tone played by the speaker using a microphone connected
to an oscilloscope or a computer. If possible, perform the Fourier transform of the signal to
determine the frequencies produced by your speaker.

Compare the frequency signatures for several tones. Suggest possible explanations for any
deviations of the signal produced by the speaker from the signal generated by the tone generator.
Writing exercise: All levels
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Write a commercial description of your plasma speaker. Include an explanation of its operation.
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Northeast Regional STEM Project