Download TE Activity: Yogurt Cup Speakers

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TE Activity: Yogurt Cup Speakers
Curricular Units
Summary
Lessons
This lesson introduces students to the role of electricity and magnetism as they build a speake
of magnets, create an electromagnet, and determine the direction of a magnetic filed. They co
cause-effect relationships by monitoring changes in the speaker's movement as the amount o
Activities
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Engineering Connection
Living Labs
The study of electromagnetism is the foundation of electrical engineering. In addition, it finds w
disciplines. For example, electromagnets are essential to the design of electric generators and
of mechanical engineers. They are also used by aerospace engineers as electromagnetic pro
for spacecraft.
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Pre-Req Knowledge
Learning Objectives
Materials
Introduction/Motivation
Vocabulary
Procedure
Safety Issues
Troubleshooting Tips
Assessment
Extensions
Activity Scaling
References
Grade Level: 6 (6-9)
Time Required: 1 hours
Group Size: 5
Activity Dependency
Expendable Cost Per Group : US$ 5
Keywords: charge, current, electricity, electromagnet, magnet, magnetic field, magnetic force
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Related Curriculum
subject areas
:
Physical Science
Problem Solving
Reasoning and Proof
Science and Technology
Educational Standards
:
American Assoc Advancement of Science Proj 2061 Science
National Science Education Standards Science
Does this curriculum meet my state's standards?
Pre-Req Knowledge (Return to Contents)
(Select state or national)
Su
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Students should know how to:
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Make a series circuit
Identify the north and south poles of a magnet
Learning Objectives (Return to Contents)
After this activity, students should be able to:
1.
2.
3.
4.
a.
b.
c.
d.
Create an electromagnetic field by running current through a wire coil.
Understand that an electric current produces a magnetic field. The stronger the current, th
Understand that electricity and magnetism are related concepts.
Describe properties and characteristics of magnets:
Magnets can be permanent or temporary.
Magnets and electromagnets attract or repel each other: similar poles repel, while dissimil
Magnets and electromagnets attract or repel another objects.
Magnets and electromagnets exert a force at a distance through a magnetic field.
Materials List (Return to Contents)
Each group needs:
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2 round magnets (½ to ¾ inch diameter)
15 ft., 20-24 gauge coil wire (enamel-coated transformer coil wire)
1 plastic container (yogurt, whip topping, butter)
1 D Cell battery
Sand paper
Electrical tape
To share with the entire class:
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Radio with detachable speakers. The output of the radio should be at least 20 watts.
Introduction/Motivation (Return to Contents)
Can you imagine life without radios? Do you know that the object that makes the speaker in th
electromagnet is created with a battery (or some other source of electricity) and a wire. A batte
Although electrons collect at the negative end of the battery, they can flow to the positive end t
generate a magnetic field. The magnetic field from one wire is quite small. By putting many wir
created. The easiest way to do this is by making the wire into a coil with many loops. The idea
simple: by running electric current through a wire coil, you can create a magnetic field. The fiel
repelled from the field of a permanent magnet in the center of the speaker. When the current in
the magnetic field. When the strength of the magnetic field changes, the attractive force betwe
changes. The changing force makes the speaker vibrate and produce sound. The bigger the v
Electromagnets are also used inside a television to generate the picture on the screen, in elec
Now that you know some applications of electromagnets, can you say what the difference betw
electromagnet is? A magnet is any material that has a magnetic field. With a regular magnet, t
on". However, there is only a magnetic field with an electromagnet when electrical current is flo
makes electromagnets more useful than permanent magnets in many applications. For examp
crane can lift and drop large masses of iron such as junk cars in a scrap yard. The three factor
electromagnet are: 1) increasing the current flowing through the coil, 2) increasing the number
the coil.
Vocabulary/Definitions (Return to Contents)
Magnet:
An object that is surrounded by a magnetic field and has the property of attract
Electromagnet: A magnet consisting of a coil of insulated wire wrapped around a soft iron core
through the wire.
Magnetic field: A region in which magnetic forces can be observed.
Magnetic
The force exerted between magnetic poles or between two electrically charged
force:
Current:
A flow of electrical charge carriers. The common symbol for current is the uppe
ampere symbolized by A.
Procedure (Return to Contents)
Background
z How can the direction of the magnetic field of an electromagnet be determined? Simi
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poles attract. Running current through a wire creates a magnetic field similar to a field
magnitude depend on the magnitude of the current and the direction of the current. T
determined by using the right hand rule:
Place the wire in your hand with your thumb in the direction of the current (point your
Close your hand so that your fingers wrap around the wire. Your fingers are pointing
How Speakers Work?
A sound is produced when a vibrating object moves the air particles around it, which in tur
ears pick up these fluctuations in air pressure and translate them into signals the brain ca
signal and translates it back into physical vibrations to create sound waves. Traditional sp
includes a permanent magnet and an electromagnet called a voice coil. The driver produc
flexible cone that is connected to the voice coil. The voice coil is a basic electromagnet. T
a constant magnetic field created by a permanent magnet. These two magnets interact wi
end of the electromagnet is attracted to the negative pole of the permanent magnet and re
constantly reverses the flow of electricity switching the north and south ends of the electro
constantly reverses the magnetic forces between the voice coil and the permanent magne
When the coil moves it pushes and pulls on the speaker cone. This vibrates the air around
Before the Activity
z Set out pairs of magnets at each table.
z Briefly review magnets and their polarities.
z Possibly bring out a speaker radio and have it playing some music.
With the Students
1. When the students enter have them explore, if they have not already started on their
other when similar poles are near each other i.e. either North to North or South to So
each other when dissimilar poles are near each other i.e. North to South or South to N
2. Distribute the remaining supplies. Have the students create an electromagnet by wind
a cylindrical object such as a C or D cell battery. Two inches of wire should be left ha
Winding the wire
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3. While keeping the wire in the shape of a coil, carefully remove the wire from the cylin
unravel.
4. Rub a piece of sand paper on each free end of the wire to remove the enamel insulat
each end.
5. Hold the ends of the wire on opposite ends of the battery to make a series circuit with
close to the magnet and observe its motion. Hook the battery up differently and see w
coil is connected to the battery in one way, one side of the coil is the north pole and th
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electromagnet. The north pole of the electromagnet will be attracted to the south pole
battery is turned around, the poles of the electromagnet are reversed.)
6. Attach the coil and a permanent magnet to the bottom of the container with either tap
such a way that the coil and magnet are next to each other. There are many different
Examples are shown in Image 2 and Image 3.
The attached magnet
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7. Connect the ends of the speaker wire to the speaker output of the radio. On the back
connect the speaker wires to. These are usually holes that the wires are stuck into. C
for example) and insert one end of the wire from the yogurt speaker into one hole, an
8. Turn the radio on and adjust the volume. When there is more current flowing through
increases. As the radio changes the current very fast, the changing electromagnetic f
vibration creates sound waves in the air, which are heard.) (See Image 4.)
9. The wires of the speaker may get hot. When electric current flows through the wire, s
heat energy due to the résistance inside the wire. If you touch the wire, the heat will t
the radio is turned up, more electricity flows through the wire and more heat is genera
the volume.
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The yogurt speaker in action
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Safety Issues (Return to Contents)
The home-made speaker wires may get hot when they are attached to the radio. This is more
high-power radios that are set at a high volume.
Troubleshooting Tips (Return to Contents)
Make sure that students completely remove insulation from the end of the wire or no current w
Assessment (Return to Contents)
Pre-Activity Assessment
Discussion Questions: Solicit, integrate and summarize student responses:
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Can we make a non-magnetic object magnetic? (Answer: Yes, this is known as magn
demonstrated with two nails. We can magnetize one nail by touching it to a magnet. T
magnetized nail is a temporary magnet. Temporary magnets retain their magnetism f
electromagnets which magnetize where the electric current is on and demagnetize w
What is a magnetic field and where do magnetic fields come from? (Answer: Magneti
electrons. The magnetic field lines give the direction in which the magnetic force acts
is strong and spread out where it is weak. For instance, in a compact bar magnet, the
towards the other. The magnetic force is strongest near the poles where these field li
the presence of magnetic field lines is a magnetic field.
Does magnetism ever wear off? (Most permanent magnets will retain their magnetism
for a very long period. This is because they are composed of electrons divided natura
into "magnetic domains" - tiny regions where all the magnetic fields of the atoms are a
pointing in the same direction. These electrons are charged and spin acting like little
electromagnets and their magnetism never wears off. It is the lining up of many, many
electron spins that creates permanent magnets. Therefore, the underlying magnetism
never wears off; only the ordering of all the spins together may become more
disordered.)
Activity Embedded Assessment
Now try this!: Have students try the following extra investigations once they have complete
their speakers.
1. Have the students change the amount of current by using more than one battery and
movement.
2. Have the students change the direction of the current by changing the wire connectio
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the speaker's movement. Can they relate the current's change in direction or change
the speaker.
3. When the speaker is connected to the radio, change the volume or add more than on
the speaker gets louder or softer? (When the volume on the radio is turned up, more
More current makes the electromagnet stronger. The stronger the electromagnet, the
on the speaker. This makes the vibrations of the speaker bigger and the speaker volu
permanent magnet or a stronger one also increases the attraction to the electromagn
the speaker. )
Post-Activity Assessment
Question/Answer: Ask the students and discuss as a class:
1. How many different forms of energy are there in the speaker circuit? (Answer: Four d
electrical, heat, magnetic, and mechanical or kinetic. If a battery were used instead of
as well.)
2. Is this circuit in series or parallel? (Answer: This is a series circuit, because there is o
3. What poles attracted or repelled? (Answer: Different poles attracted and like poles re
4. Was there a conductor, insulator or both used? (Answer: Both a conductor and an ins
and the coating around the outside of the wire is the insulator.)
5. How could you increase the strength of the speaker/electro-magnet? (By wrapping m
the current in the circuit, or by doing both.)
OR
Evaluation Rubric: In addition to the questions above, teachers can use the scoring rubric
student work. The rubric evaluates understanding the purpose of the experiment, the relat
ability to develop hypotheses and make logical conclusions.
Evaluation Rubric
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Activity Extensions (Return to Contents)
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Make another coil with more windings to wrap around the cell battery.
Dissect a real speaker and compare to the one used in this activity.
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Observe the interaction between two electromagnets.
Connect multiple round magnets to the yogurt cup. The speaker should be louder.
Activity Scaling (Return to Contents)
For upper grades
Knowing that there are 3 variables that influence these electromagnetic coils/speakers (cu
current ), have the students devise an experiment on their own to test each of the variable
References (Return to Contents)
AAAS Benchmarks Educational Standards. Accessed May 29, 2006 at
http://www.teachengineering.com/browse_standards.php?
matching=false&code=empty&lowgrade=empty&highgrade=empty&type=empty&subtype=
Knowledge Representation Laboratory. K-12 Electromagnetism and Magnetism. Accessed Ma
http://kr.cs.ait.ac.th/~radok/physics/k12.htm
Lynne Nolan. Illinois Institute of Technology. Magnets, Electromagnets, and Motors. Accessed
http://www.iit.edu/~smile/ph9215.html.
Magnificent Magnets. Accessed May 08, 2006 at
http://staff.jsr.cc.va.us/asullivan/eisenhower/projects/magnificent_magnets.htm
Marshall Brain. HowStuffWorks. How Electromagnets Work. Accessed May 08, 2006 at
http://science.howstuffworks.com/electromagnet2.htm
McREL National Educational Standards. Accessed May 29, 2006 at
http://www.mcrel.org/compendium/search.asp
Schoolscience. Electromagnets. Accessed July 7, 2006 at
http://www.schoolscience.co.uk/content/3/physics/copper/copch33pg1.html
SC Science Curriculum Standards. Accessed May 29, 2006 at
http://www.myscschools.com/offices/cso/standards/science/default.cfm
The UIUC Physics Van Outreach Program. Magnetism Wearing Off. Accessed May 08, 2006 a
http://van.hep.uiuc.edu/van/qa/section/Electricity_and_Magnets/Magnets/2002040813373
Tom Harris. HowStuffWorks. How Speakers Work. Accessed July 7, 2006 at
http://electronics.howstuffworks.com/speaker.htm.
Wikipedia, the free encyclopedia. Magnet. Accessed May 08, 2006 at
http://en.wikipedia.org/wiki/Magnet.
Owner (Return to Contents)
Center for Engineering and Computing Education, University of South Carolina
Contributors
Jed Lyons, Ph.D., P.E., Ivanka Todorova, Trevor Roebuck
Copyright
© 2006 by Center for Engineering and Computing Education, College of Engineering and Infor
Carolina, Columbia, SC,
http://cece.engr.sc.edu
Last Modified: November 5, 2008
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