Auburn University



Electricity Rocks!

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Electromagnetism

Engineering Teaching Kit

TABLE OF CONTENTS

TABLE OF CONTENTS………………………………………………………………………………………….1

TEACHING KIT OVERVIEW…………………………………………………………………………………2

UNIT OUTLINE……………………………………………………………………………………………………..4

MATERIALS LIST…………………………………………………………………………………………………..5

TEACHING PREP MATERIAL………………………………………………………………………..6 – 17

> DAY 1 BRIEFING…………………………………………………………………………………..…6

> DAY 2 BRIEFING……………………………………………………………………………………..8

> DAY 3 BRIEFING…………………………………………………………………………………...12

> DAY 4 BRIEFING……………………………………………………………………………………16

> DAY 5 BRIEFING……………………………………………………………………………………17

PICTURE CREDITS, REFERENCES.…………………………………………………………………….18

STUDENT PACKET…….………………………………………………………………………………..19 – 34

> DAY 1…………………………………………………….………………………………………..20 – 22

– “What is Engineering?”.......................................……………………………….20

– “Historically Speaking”........................................……………………………….21

– “Sounds Great!”.......................................………………………………………….22

> DAY 2………………………………………………………..…………………………………….23 – 26

– “It’s Electric!”........................................…………………………......................23

– “Got Magnetism?”........................................………………………………………25

– “Electromagnetic Induction”......................………………………………………26

> DAY 3………………………………………………………………………………………………27 – 30

– “Building a Speaker”.......................................…………………………………..27

– “Building Worksheet”........................................………………………………..29

– “Results Table”.......................................……………………………………………30

> DAY 4 – “Design, Test, Repeat…”......................................……………………………32

> DAY 5 – “Evaluation Survey”.......................................………………………….34 – 35

TEACHING KIT OVERVIEW

Grade Levels: 6, 7, 8

Subjects:

• Science/Physics

• Engineering/Technology

Duration: five 50-minute sessions

Description: In this lesson, students learn about the connection between science and engineering. They explore the technological applications of electricity, magnetism, and sound. Students are given an engineering design challenge, in which they must design, build, test, and optimize a simple electro-mechanical speaker.

Engineering Connection:

• Students learn principles of electricity, magnetism, and sound, and use this knowledge to design, build, test, and optimize speakers.

Educational Standards:

• Virginia Standards of Learning (SOL):

• PS.8 (Physical Science) The student will investigate and understand characteristics of sound and technological applications of sound waves.

• 6.2 (Grade 6) The student will investigate and understand basic sources of energy, their origins, transformations, and uses. Key concept is energy transformation.

• 6.4 (Grade 6) The student will investigate and understand basic characteristics of electricity. Key concepts include

i. Electrical energy can be produced from a variety of energy sources and can be transformed into…other form[s] of energy

ii. Electricity is related to magnetism

iii. Currents are either alternating or direct

• PH.8 (Physics) The student will investigate and understand that energy can be transferred and transformed to provide usable work. Key concepts include:

i. Transformation of energy among forms including mechanical…[and] electrical

ii. Efficiency of systems

UNIT OUTLINE

Day 1 – Engineering & Sound

• Objective: To understand the principles of sound

1. Introduction to Engineering

a. What is engineering?

b. History of speakers

i. Examples of speakers

2. Sound

a. Pitch

b. Volume

c. Transmission through media

3. ACTIVITY 1: Observing different sound frequencies using a ruler

4. Worksheets: “What is Engineering?”, “Historically Speaking”, “Sounds Great!”

Day 2 – Electricity & Magnetism

• Objective: To understand the principles of electricity, magnetism, and electromagnetism

1. Electricity

a. Current

b. Voltage

c. Resistance

d. Power

2. DEMO1: Water pump illustrating current flow and resistance

3. Magnetism

a. Poles

b. Magnetic fields

4. DEMO 2: Magnetic force at work

5. Electromagnetic coils

a. Field strength as a function of number of turns

b. Right hand rule

6. ACTIVITY 2: Electromagnet (magnetized nail)

7. Worksheets: “It’s Electric!”, “Got Magnetism?”

Day 3 – Speaker Construction

• Objective: To understand how a speaker works

1. DEMO 4: Standard (Ordinary) speaker and Paper Cup (Extraordinary) speaker

2. ACTIVITY 3: Variations of a basic speaker

3. Worksheets: “Building a Speaker”, “Building Worksheet”, “Results Table”

4. Material selection

5. Instruct students to bring in materials for the following day

Day 4 – Design & Testing

• Objective: To understand how engineers design and how to apply these principles to the competition

• Objective: To test initial speaker designs and present a final design

1. The Engineering Design Process (10 min)

2. Worksheet: “Design, Test, Repeat”

3. ACTIVITY 4: Open build (40 min)

Day 5 – Design Competition

1. ACTIVITY 5: Team Competition (30 min)

2. Class Discussion: Concept Review (10 min)

3. Evaluation Survey (5 – 10 min)

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The “Electricity Rocks” Team:

Scott Simmons, Ben Jessup, Chiedo Ohanyerenwa,

Chris Hemp, Coles Jennings, Marija Cvijetic, Eddie Pan

Materials List

(All quantities are per group, unless otherwise noted)

Day 1

• 12” Plastic Ruler (1/student)

Day 2

• 2” Galvanized Nail (1)

• 3” Galvanized Nail (1)

• 4” Galvanized Nail (1)

• A few paper clips

• Insulated Copper Wire, 22 AWG (approx. 3 ft.)

• C Cell Battery (1)

• Small strips of electrical tape (2)

• Bar magnet (1)

• Plastic sleeve (1)

• 30AWG enamel wire (approx. 10 ft.)

• D-cell battery holder with switch (1)

• D-cell battery (1)

• Small piece of sandpaper (1)

• One-way hand pump (1)

• ½” clear plastic tubing (approx. 4 ft.)

• Bucket (1)

• Plastic zip ties (around 10)

Day 3

• IPOD

• Commercial (25 W) computer speakers

• Ready-made speaker (Styrofoam cup, magnet, coil of wire)

• Plastic cup (1)

• Paper cup (1)

• Small disk magnet (1)

• Small donut magnet (1)

• 30AWG enamel wire (approx. 10 ft.)

• Small piece of sandpaper (1)

• Sound meter

Days 4 & 5

• (Same as Day 3 plus students’ own materials)

DAY 1 Briefing

What is engineering?

Engineering is the application of science to solve human problems and meet human needs.

History of speakers

People have known about acoustics and mechanical amplification of sound since ancient times. The first electromagnetic speakers were developed in the middle of the 19th century in the United States with the development of the telephone. Antonio Meucci, Alexander Graham Bell, and Elisha Gray, working separately, all produced their own versions of the telephone, which included speakers to convert an electrical signal into sound. The first conical paper diaphragm speaker was described in 1901 by John Stroh in Britain. Speaker development continued from then until the present day, with variations on the fundamental designs as well as refinements to improve sound quality.

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|Armature Speaker, circa 1882 (2) |Direct Radiator Speaker, circa 1961 (2) |

Examples of speakers

• Stereo systems

• Car horn

• Telephone

• Computer speaker

• Megaphone

Sound Overview:

Sound is a longitudinal (compression) wave traveling through a medium (solid, liquid, or gas) which is received by a human ear and interpreted by the brain.

Pitch: the highness or lowness of a sound, and is determined by the frequency and wavelength of the sound wave.

Volume: the loudness of a sound (measured in decibels, or dB), and is determined by the amplitude of the sound wave.

Transmission through media: Sound requires a media in which to move. It is

transmitted by the molecules within the media displacing each other in sequence along

a given direction. Because of this, denser media produces better sound

transmission and sound cannot be travel in a total vacuum (like outer space)

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Goal: To demonstrate the relationship between the frequency and pitch of a sound wave using a simple vibrating lever.

Materials (per student):

• 12” Plastic Ruler (1)

Preparation: None

Instructions: This activity is a very simple means of showing the relationship between frequency and pitch. Students take the ruler and clamp it against the edge of the table with one hand, leaving part of it hanging over the edge of the table. Then students flick the ruler with the other hand, causing it to vibrate and make a distinct sound. The pitch of this sound can be altered by clamping the ruler at different points along its length, causing it to vibrate at different frequencies.

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Clamping the ruler closer to the end (left) will cause a slow vibration and lower pitch. Clamping it towards the middle (right) will increase the frequency and produce a higher pitch. Students can experiment and even make simple songs with this crude musical instrument.

SAFETY NOTICE: An overzealous student could break a cheap ruler and possibly inflict harm when it snaps. Emphasize that a gentle flick is all that’s needed to produce a tone.

DAY 2 briefing

Electricity Overview:

CURRENT, I: a flow of electric charge, measured in amperes (or Amps, A).

VOLTAGE, V: the amount of potential energy per unit charge, measured in Volts (V), sometimes referred to as “electrical pressure.”

RESISTANCE, R: the property of a material to restrict the flow of electric charge, measured in ohms (Ω).

POWER, P: the rate of electrical energy transformation (into heat, light, or mechanical action), measured in watts (W).

Magnetism

MAGNETIC POLE: the faces of a magnet (there are always two, North and South). They have opposite polarity and at either location the magnetic effect is the strongest.

MAGNETIC FIELD: A magnetic force exerted by the magnet on the area around it. We can draw field lines to show the direction of the magnetic field at any given point.

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Magnetic field lines around a bar magnet ( 3)

ELECTROMAGNETISM: A wire carrying current (I) produces magnetic field (B), aligned centripetally with the wire’s center according to what is known as the “right hand rule” – where the thumb points in the direction of the current, and the fingers curl around in the direction of the magnetic field lines. The reverse case also holds.

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|Electromagnetic Field (3) | |The Right Hand Rule (4) |

When wire carrying a current is looped into a coil, the magnetic field produced inside the coil is magnified, such that it is proportional to the number of turns (loops) in the coil (i.e. a coil with more turns produces a more powerful magnetic field relative to a coil with fewer turns, all other factors being the same).

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Goal: To demonstrate the fundamentals of electromagnetism through a simple battery powered electromagnet.

Teacher Tools:

• Wire Strippers

Materials (per group):

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Preparation: Students should be divided into small teams of two or three, each team given the materials listed above. A small amount of insulation should be removed from each end of the wire strands, to allow for proper electrical connection to the batteries.

Instructions: Each group should construct a simple electromagnet (pictured below). The wire is coiled around a galvanized nail, ensuring that the coils are kept tight and neat to maximize the magnet’s strength. Enough wire should be left for leads to the battery. One lead should be attached to the positive end of the battery and one to the negative using electrical tape (although shock risk is very small for a C cell battery, the tape is a safety precaution). The students should be able to demonstrate how current flowing through the wire coils magnetizes the nail by picking up paper clips with the electromagnet.

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Wire Coiled Around a Nail (5)

Have the students experiment with different nail sizes, number of coil windings, and double or triple-wrapping the wire in a small area rather than over the length of the nail. This should give insight into what creates the strongest magnetic field.

SAFETY NOTICE: Although shock risk is minimal, the wire can heat up after some time if the magnet is not disconnected. Make sure students do not leave an electromagnet connected for more than 5 minutes at a time.

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Goal: To illustrate the basic concepts of voltage, current, and resistance, and Ohm’s law through analogy to the flow of water.

Materials:

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Background: The flow of electricity is readily compared to the flow of water. A water hand pump will be used to illustrate the flow of electricity in a close circuit. The water is moved when the pump is pulled upwards. The pressure applied during this upward stroke is analogous to the voltage in an electric circuit, and the speed of the flowing water is similar to the current. If more force is applied during the upward stroke, the water will move faster, just as more voltage increases current in a circuit. Lastly, the diameter of the tubing is similar to the resistance in a circuit. A smaller diameter tube is the same as a higher level of resistance. So, in the water loop, if the tube diameter is decreased, the water will move faster if the same pressure is applied, or a smaller pressure must be applied to get the same speed of flow. This relationship between water pressure, water speed, and tube diameter clearly illustrates Ohm’s law (voltage (V) = current (I) x resistance (R)).

Preparation: Attach the plastic tubing to the pump inlet on the bottom. Then, place the other end of the tubing in a bucket full of water and pump a few times to draw water into the pump. Take care to pump slowly, as water will pour out of the side outlet once the pump is full and pumping too hard will spray water everywhere. Next, close the loop by attaching the open end of the tubing to the pump’s side outlet. Try to minimize the amount of air in the tube, so that air bubbles do not interfere with the demonstration.

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The left image shows the pump being filled, followed by the closed loop on the right.

Instructions: As described above, this closed water loop demonstrates Ohm’s law. Have students use the hand pump to see the relationship between hand pressure and the speed of the water flow. Then, tighten the pipe with a zip tie to simulate increased resistance. Students should observe that the same amount of force moves the water at greater speeds.

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Goal: To illustrate the movement of a magnet by a wire coil

Materials:

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Instructions: Coil the wire tightly around the plastic sleeve, keeping about two inches of slack at the beginning for connection to the battery holder. Coil the wire neatly and evenly, making sure that there is no space from one coil to the next. Then, use the sandpaper to strip the enamel off both ends of the wire, and connect these ends to the two leads from the battery holder, making sure the switch is off. Insert a magnet into the sleeve, so that it is sitting close to the beginning of the coils. Once you connect the switch, the magnet should jump a little bit in one direction or the other.

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To make the magnet jumping more obvious, try tapping the switch rapidly. This vibrates the plastic sleeve, and is a good first hand illustration of the fundamentals behind a speaker.

SAFETY NOTICE: Due to the low resistance of the wire alone, keeping the switch on more than 10 or 15 seconds will cause the wire to heat up.

DAY 3 briefing

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Goal: To compare and contrast the features and functionality of a typical computer speaker (“ordinary speaker”) and the simple paper cup speaker (“extraordinary speaker”).

Materials:

• IPOD, (A portable CD player, or a standard headphone out jack of a computer would work as well)

• 2 standard computer speakers

• Constructed paper-cup speaker prototype

• Sound meter (1)

Instructions: Plug in your commercial audio player (or computer) to the standard audio input plug of the computer speakers. Plug in the power adapter from the speakers into a standard power outlet and play a reselected music selection for the student. Measure the intensity of sound coming out of the speakers using the sound meter and have the students make note (not necessary to record) of the different dB values as you adjust the volume of the player. Next, disconnect the sound source from the speakers and connect the audio input source to the pre-built prototype paper-cup speaker (which is constructed through the instructions in the following section). Use alligator clips and to secure the wires on either side of the connection. Once again turn on your sound source and measure the intensity of sound coming from the paper cup speaker. The students should be able to hear a faint and crackly sound coming out of the speaker but at a much lower volume than before.

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SAFETY NOTICE: Using an audio source with a high output resistance (i.e. a boom box “speaker out” output) will cause the connection wires to heat up which could in turn cause the cup and/or wires to melt, and the internal boom box circuit breaker to trip.

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Instructions: Coil the wire tightly around the plastic sleeve, keeping about two inches of

1. Measure 4 inches of wire from the spool. While holding the wire to a pen of desired diameter, begin wrapping the wire around the pen, leaving the 4 inches free so that it can be used to connect the input to the speaker. Using your finger to hold the wire to the pen, count the number of times that the wire passes your finger as you wrap the wire around the pen. Each time you wrap the wire entirely around the pen, you create one coil. Be sure not to wrap the wire around the pen too tightly, the coils will have to be removed from the pen. After you have created the selected number of coils, cut the wire from the spool, making sure to leave a second 4 inches to use as the other input connection of the speaker.

2. Using a small piece of sandpaper, remove the insulation from a length ½ inches from the end of the two input wires.

3. Remove the coil from the pen. Using the scotch tape, attach the coil to the center of the bottom of the cup. To do this, place the cup upside down on the work surface. Attach the coil so that it is flat against the surface of the cup, leaving two 4-inch input wires free.

4. Using the scotch tape, attach the magnet on top of the coil. Again lay the magnet flat.

5. Attach one of the alligator clips from the connecting cable to one of the wires on your cup speaker. Attach the other alligator clip to the remaining input wire on the speaker.

6. Plug the other end of the connecting cable into the microphone jack of your electronic device. Make sure the volume of your electronic device is set to “high.”

7. Arrange the sound meter so that the microphone is pointed at the opening of your cup speaker. Place the sound meter 6 in from the opening and turn it to the 70 dB range.

8. Play a pre-selected selection from a recorded song and use the sound meter to record the intensity of the sound coming from your paper cup speaker.

Splitting Up Into Teams:

Students should be split up into groups of 2 or 3. Each group will be given (at random on of the following design variations to explore). Each group will then test their design by measuring the sound output (using the sound meter) and record their results on the blackboard. Each student will copy down the results from the different groups and analyze the implications of the different designs on a worksheet.

A. Paper cup, small magnet, d=¼” coil Example Data Table:

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

B. Paper cup, donut magnet, d=¼” coil

C. Plastic cup, small magnet, d=¼” coil

D. Paper cup, small magnet, d=½” coil

E. Paper cup, donut magnet, d=½” coil

F. Plastic cup, small magnet, d=½” coil

Students should be reminded to bring in materials from home in order to design and build their own speaker!

Tips for selecting materials for building a good speaker:

When creating the speakers, seek rigid materials for the enclosure and flexible materials for the diaphragm. If the enclosure and diaphragm are integrated, finding a material that is partially rigid and partially flexible is best (e.g. paper cup).

• Integrated enclosure & diaphragm

o Styrofoam

o paper cups

• Enclosure

o Plastic bottles

o Cardboard

o Construction paper

o Wood

• Diaphragm

o Paper

o Rubber Cross sectional view of a typical stereo speaker (6)

o Aluminum foil

o Tape

Day 4 Briefing

Discussion: How does an engineer differ from a scientist?

>> Engineers apply a logical methodology to develop solutions to practical problems.

The Engineering Design Process

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Goal: To expose students to the engineering design process, team building, optimization and open-ended problem solving.

Materials:

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Instructions: Starting with the basic prototype from the previous day, students should now modify the design in order to achieve the highest possible volume output. They may use appropriate materials that they brought in from home. This is a team activity and group collaboration is encouraged and emphasized. Before and after the activity, each group should take a few minutes to answer the guide questions on their worksheet.

DAY 5 briefing

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Goal: To foster and encourage a healthy competitive attitude among the students, and to give them the opportunity to observe the strengths and weaknesses of alternative solutions to the problem (i.e. alternative designs)

Materials:

• Sound meter (1)

Instructions: The students should be given 2 minutes to come up with any last minute “tweaks” with their design. The groups should then come up and measure their sound output one by one and the results of each group should be recorder on the board. If time permits, the groups can also give a brief (< 1min) explanation of their specific design and why they think it worked well or poorly in the end. After each team has gone up and measured its speaker’s audio output, the winner will be determined as the team with the loudest speaker. The prize for winning the competition is at the discretion of the instructor.

Discussion and Review (approx 10 min., Q&A style):

(Key points to cover):

>> What is engineering? How is it different from science?

>> Who invented the first speaker? For what purpose?

>> How does sound travel?

>> Which scientific term essentially means “pitch?” What about “Volume?”

>> What is the basic idea behind electromagnetism?

>> What makes a speaker design better?

>> What is the first step in the engineering design cycle?

After reviewing the important concepts, the students will fill out an evaluation survey dealing with their experiences throughout the weeklong activity.

PICTURE CREDITS

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ADDITIONAL REFERENCES

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2) Giancoli, D. C. (2000). Physics for Scientists & Engineers, 3rd Ed. Upper Saddle River, NJ: Prentice Hall.

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Electricity Rocks!

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Student Packet

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DAY 1: Historically Speaking

As previously mentioned, engineers apply the principles of science to create new technology which solves a problem and addresses a need in society. One good example - the need for long-distance communication - was first addressed successfully in the 1870's. The key players at the time, Alexander Graham Bell, Elisha Gray, and Antonio Meucci each worked towards a common goal of developing a device that would allow two people to talk to each other through a device that allowed them to be in different physical locations. The patent, which was first awarded to Bell, described the new "telephone" as an "apparatus for transmitting vocal or other sounds telegraphically." However in addition to transmitting sound, the apparatus had to ensure that the users could hear each other. This was a huge challenge to which the answer was first primitive loudspeaker, a transducer capable of converting electricity to sound using a very straightforward implementation.

Alexander Graham Bell using his telephone (14) Inside Bell’s first telephone (15)

Some different speaker styles:

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Each type of speaker design employs the same concept of combining an electrical current and a magnetic field to produce vibrations.

Transmission of Sound

In general, sound must be transmitted through a medium. The two most common media for the transmission of sound are air and water. Sound travels faster in denser media, so sound transmitted through water will travel faster than sound transmitted through air.

-- Can you think of an application of the transmission of sound through water?

-- What else can you transmit sound through?

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DAY 1: What is engineering?

Starting today and for the next five days everyone in this room will become an engineer. Ask the average person a hundred years ago what it is that an engineer does and he would probably tell you "An engineer works on the railroad." Back then, that statement would have been correct, but nowadays, it is practically a joke. So then what do engineers do and moreover, what is engineering? To most people engineering and science mean about the same thing: exploring the natural world and discovering new laws and such (oh yeah, and lots of equations). In reality, engineering is very different from science. Engineers apply the principles of science to create new technology which solves a problem of addresses a need in society.

Who do you think of when the term engineer is mentioned?

Thomas Edison?

Famous Inventor

Leonardo Da Vinci?

Painter, inventor, engineer

Eli Whitney?

Inventor of the cotton gin

Alexander Graham Bell?

Invented the telephone

Rudolf Diesel?

Developed the diesel engine

Nikola Tesla?

Developed alternating current

Jimmy Carter?

39th President/Nuclear Engineer

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DAY 1: SoundS GREAT!

Sound is energy transmitted in waves. Each sound wave is characterized by its own amplitude, frequency and wavelength. These characteristics also describe the pitch and the volume of the transmitted sound.

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AMPLITUDE: the distance from the resting position to either the crest or the trough of the wave

FREQUENCY: the number of waves that pass a point during one second, expressed as Hertz, (Hz).

WAVELENGTH: the distance between a point on one wave and the identical point on the next wave

PITCH: the highness or lowness of a sound, and is determined by the frequency and wavelength of the sound wave.

VOLUME: the loudness of a sound (measured in decibels, or dB), and is determined by the amplitude of the sound wave.

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How can you vary the amplitude of the sound waves created by holding one end of a ruler on the desk and smacking the other end?

How about varying the frequency? The wavelength?

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DAY 2: IT’S ELECTRIC!

“Energy and persistence drive all things”

-- Benjamin Franklin

Ever been struck by lighting? Benjamin Franklin was, and even he lived to tell about it. What he went on to tell was the story of electricity: its existence not only in the form of lightning but in ordinary things around us. By now you have probably studied electricity many times, but today you’re going to develop an intuitive feel for it really is!

Depiction of Franklin’s famous kite experiment (20) Lightning strikes the ground (21)

CHARGE: a property of matter (like weight or height) that represents the quantity of unbalanced electricity in a body. It can be either positive or negative (that much you already knew) and is measured in terms of the unit Coulomb ( C ).

ELECTRONS: negatively charged particles (i.e. very tiny “things”). How tiny? Well, each electron weighs only 0.0000000000000000000000000000000919 kg

ELECTRIC CURRENT: which is abbreviated with the symbol “I” and simply means how many electrons are flowing (traveling) per unit time. The unit of current is Amperes, (A) and is equivalent to Coulombs/sec. So naturally this means that the more electrons we have and the faster they are traveling (flowing) the more current we have.

VOLTAGE: Imagine holding a basketball a few inches off of the ground. If you dropped it on your toe from this height, it probably wouldn’t hurt; but what about if you dropped it from 2 stories up? The ball’s potential energy is a lot higher so dropping it this time would most surely hurt! Now imagine doing the same thing except this time instead of 1 basketball, you have one hundred. Intuitively, how much greater would the impact be then?

Answer: _________ times

If instead of holding basketballs you’re holding electrons, we can think of their potential energy as proportional to their height off the ground. We have already determined that dropping 100 basketballs on your foot from this height is A LOT worse than dropping just one, so there we have it:

The difference in potential energy per unit of charge (i.e. the drop height per basketball) is known as VOLTAGE.

RESISTANCE: What if instead of dropping the original basketball through air from 2 stories up, we dropped it instead into a big vat of honey that was 2 stories deep? Would it be harder for the ball to fall in this case or easier? Answer: __________________

The difficultly with which a charge travels through some medium is known as the RESISTANCE of that medium, abbreviated R, and measured in terms of Ohms (Ω).

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The last and perhaps most useful term left to define is ELECTRICAL POWER. Power is defined as the amount of electrical energy per unit time and its unit is Watts (W).

You may be more familiar with electrical power by its common name: ELECTRICITY!

VOLTAGE = CURRENT x RESISTANCE ( V = I x R

POWER = VOLTAGE x CURRENT ( P = I x V

Use your new electrical intuition to answer the following Questions:

More Resistance + Less Voltage = __________ Current

More Voltage + Less Current = __________ Resistance

More Current + More Resistance = __________ Power

In cars, engine power is measured in units of Horsepower:

The 2006 100%-electric, 248-horsepower Tesla Roadster (26)

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DAY 2: Got magnetism?

If you have ever used a compass, you might have heard that the compass “North” actually points to the Earth’s south geographic pole. The Earth (like a refrigerator magnet) has its own MAGNETIC FIELD, B (with units of Tesla, T) which points from the North to the South MAGNETIC POLES. This field essentially represents the MAGENTIC FORCE of the magnet acting at a distance from the poles.

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Many materials exhibit naturally magnetic properties, the most common of them being iron. The Earth’s innermost core is made up of molten iron which is essentially responsible for Earth’s strong magnetic field – think of it as a very large bar magnet.

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Like oppositely charged particles, opposite magnetic poles attract while like poles repel. This behavior is more than just a striking coincidence but in fact demonstrates the strong fundamental relationship between electricity and magnetism. This can be summarized as:

Electricity INDUCES Magnetism

And

Magnetism INDUCES electricity

This essentially means that there is no separate electric force

(between charges) and magnetic force (between poles). They

are both the same force acting in different ways, and this

is the basic principle known as ELECTROMAGNETISM.

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DAY 2: ELECTROMAGNETIC INDUCTION

Right Hand Rule:

Version I.>

Version II.>

The number of coils through which the current travels has an effect on the magnetic field.

Question: Intuitively, what do you think happens to the strength of the magnetic field as we increase the number of coils though which the current is flowing?

Answer:___________________________________________________________

The Right Hand Rule is a visual illustration of ELECTROMAGNETIC INDUCTION: the physical explanation of the inseparable nature of electricity and magnetism. It is the basis behind the operation of virtually all electrical devices in the world today. The concept was discovered long ago but was finally harnessed at the beginning of the 20th century by a brilliant engineer named Nikola Tesla. His discovery known as ALTERNATING CURRENT explains the electricity that comes out of your wall outlet and operates like this:

By flipping the direction of the current flowing through a circuit every X seconds we are able to toggle the resultant magnetic field back and forth. This periodic flip generates a sort of push and pull action on a permanent magnet placed in the vicinity of the varying magnetic field. Can you think of any reasons why this might be a useful thing?

Answer:__________________________________________________

_____________________________________________________________

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DAY 3: Building a Speaker

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1. Measure 4 inches of wire from the spool. While holding the wire to a pen of desired diameter, begin wrapping the wire around the pen, leaving the 4 inches free so that it can be used to connect the input to the speaker. Using your finger to hold the wire to the pen, count the number of times that the wire passes your finger as you wrap the wire around the pen. Each time you wrap the wire entirely around the pen, you create one coil. Be sure not to wrap the wire around the pen too tightly, the coils will have to be removed from the pen. After you have created the selected number of coils, cut the wire from the spool, making sure to leave a second 4 inches to use as the other input connection of the speaker.

2. Using a small piece of sandpaper, remove the insulation from a length ½ inches from the end of the two input wires.

3. Remove the coil from the pen. Using the scotch tape, attach the coil to the center of the bottom of the cup. To do this, place the cup upside down on the work surface. Attach the coil so that it is flat against the surface of the cup, leaving two 4-inch input wires free.

4. Using the scotch tape, attach the magnet on top of the coil. Again lay the magnet flat.

5. Attach one of the alligator clips from the connecting cable to one of the wires on your cup speaker. Attach the other alligator clip to the remaining input wire on the speaker.

6. Plug the other end of the connecting cable into the microphone jack of your electronic device. Make sure the volume of your electronic device is set to “high.”

7. Arrange the sound meter so that the microphone is pointed at the opening of your cup speaker. Place the sound meter 6 in from the opening and turn it to the 70 dB range.

8. Play a pre-selected selection from a recorded song and use the sound meter to record the intensity of the sound coming from your paper cup speaker.

|Name: | |

DAY 3: BUILDING WORKSHEET

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What design options were you assigned?

No. of Coils ___________ Diameter of Coils______________

Record your results below:

|Magnet Type: |Cup Type: |Measured Sound Level (dB) |

|Small |Paper | |

|Donut |Paper | |

|Small |Plastic | |

1. It is important which alligator clip is attached to which wire? Why do you think this is?

2. Why is it important to play a pre-selected selection from a recorded song? Remember you will be attempting to optimize your speaker design!

|Name: | |

DAY 3: Results TABLE

A. Paper cup, small magnet, d=¼” coil B. Paper cup, donut magnet, d=¼” coil

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

C. Plastic cup, small magnet, d=¼” coil D. Paper cup, small magnet, d=½” coil

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

E. Paper cup, donut magnet, d=½” coil F. Plastic cup, small magnet, d=½” coil

|# of Coils |Measured Sound Level (dB) |

|15 | |

|20 | |

|25 | |

|# of Coils |Measured Sound Level (dB) |

|15 | |

|0 | |

|25 | |

3. Comparing values in each table, which no. of coils produced the loudest sound? Why?

4. Comparing values in tables A and B which magnet produced the loudest sound? Why?

5. Comparing values in tables A and C, which cup produced the loudest sound? Why?

6. Comparing values in tables A, B, and C with those in D, E, and F, which coil diameter produced the loudest sound? Why?

For next class remember to bring in materials from home in order to design and build your own speaker!

Here are some tips for selecting materials to build your own speaker:

When creating the speakers, seek rigid materials for the enclosure and flexible materials for the diaphragm. If the enclosure and diaphragm are integrated, finding a material that is partially rigid and partially flexible is best (e.g. paper cup).

• Integrated enclosure & diaphragm

o Styrofoam

o paper cups

• Enclosure

o Plastic bottles

o Cardboard

o Construction paper

o Wood

• Diaphragm Cross sectional view of a typical stereo speaker (6)

o Paper

o Rubber

o Aluminum foil

o Tape

|Name: | |

Day 4: Design, TEST, REPEAT…

How does an engineer differ from a scientist?

A scientist may perform an experiment to determine the thrust produced by a rocket. On the other hand, an engineer may take the results of the experiment and design a better rocket or a vehicle that uses the rocket. Let’s look at engineering design in detail.

The Engineering Design Process

Engineers apply a step-by-step design process to develop solutions to problems.

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How can this methodology be applied to the design of a speaker?

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Before you get started with your design take 5 minutes to answer the following questions:

1. What is your design problem?

2. Brainstorm some ideas here:

3. What design did you select to build and why?

For the last five minutes of class, answer the following questions regarding your design.

4. What worked well in your first design?

5. What did not work well in your first design?

6. What changes are you going to make to your design and why?

|Name: | |

DAY 5: Evaluation Survey

1. How much did you learn (really) ?

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2. How much fun was this experience (really) ?

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3. How challenging was this experience?

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4. How successful was your speaker ?

[pic]

5. How much did you enjoy working in a team?

[pic]

6. How much did everyone on your team contribute?

[pic]

7. Are you more likely to go into engineering after this experience?

[pic]

8. How well do you understand what engineering is about?

[pic]

9. How well do you understand sound?

[pic]

10. How well do you understand electricity and magnetism?

[pic]

11. How well do you understand the design process?

[pic]

12. Were the UVA students effective teachers?

[pic]

13. What were we trying to teach you?

14. What was best part about this experience?

15. What about the worst part?

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1 2 3 4 5 6 7 8 9 10

Insulated Copper Wire,

22 AWG (approx. 3 ft.)

C Cell Battery (1)

Strips of electrical tape (2)

Bar Magnet (1)

* 30AWG enamel wire (approx. 10 ft.)

* D-cell battery holder with switch (1)

2” Galvanized Nail (1)

3” Galvanized Nail (1)

4” Galvanized Nail (1)

A few paper clips

Bucket (1)

Plastic zip ties (approx 10)

D-Cell Battery (1)

Plastic Sleeve (1)

Small piece of sandpaper (1)

Students’ materials from home

Sound Meter (1)

Small piece of sandpaper (1)

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

1 2 3 4 5 6 7 8 9 10

Very Much!

No Opinion

Not at All

One-way hand pump (1)

* ½” clear plastic tubing (approx. 4 ft.)

Small disk or donut magnet (1)

30AWG enamel wire (approx. 10 ft.)

Plastic or paper cup (1)

Revise

Design

Develop

Final Report

(13)

(12)

Test Design

Develop

Design

Brainstorm

Ideas

Identify

Problem

(11)

(10)

(9)

(8)

(7)

Start with your right palm open and the thumb pointing upward. Curl the fingers of your right hand towards your palm to represent the flow of current in a circular coil of wire. Your thumb will point in the direction of the resultant magnetic field induced from the flow of current.

Start with your right palm open and the [?]EFGXYZkïÝϸ¦”†teYJ=1%h´>‚hÂ"Œ5?OJQJhÿ8CJ(OJQJaJ(hòhÒh >îOJQJ^J[?]h?UÄh?UÄCJ(OJQJaJ(hJnÚCJ(OJQJaJ(h™oH5?CJ4OJQJ^J[?]aJ,#hw2Gh?[”5?CJ4OJQJ^J[?]aJ,hòhÒCJ,OJthumb pointing upward. Your thumb represents the direction of the flow of current. If you curl the fingers of your right hand towards your palm, then your curled fingers will point in the direction of the resulting magnetic field that will arise from the flow of current (your thumb).

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