Subject:​ ​Physics    

Build​ ​Your​ ​Own​ ​Speakers     Required​ ​time:​ ​120​ ​minutes​ ​(2​ ​hours)  Number​ ​of​ ​Students:​ ​20  Standards:   California​ ​Science​ ​Standards,​ ​Public​ ​Schools,​ ​Physics  ● Students​ ​know​ ​magnetic​ ​materials​ ​and​ ​electric​ ​currents​ ​(moving​ ​electric  charges)​ ​are​ ​sources​ ​of​ ​magnetic​ ​fields​ ​and​ ​are​ ​subject​ ​to​ ​forces​ ​arising​ ​from  the​ ​magnetic​ ​fields​ ​of​ ​other​ ​sources.  ● Students​ ​know​ ​changing​ ​magnetic​ ​fields​ ​produce​ ​electric​ ​fields,​ ​thereby​ ​inducing   ● currents​ ​in​ ​nearby​ ​conductors.  

  Goals   ●

Students​ ​will​ ​be​ ​introduced​ ​to​ ​basic​ ​concepts​ ​such​ ​as​​ ​electricity,​ ​magnetism,  and​ ​electrical​ ​components​.​ ​After​ ​that,​ ​participants​ w ​ ill​ ​construct​ ​a​ ​homemade  speaker​. 

   

Materials​ ​Needed   Total​ ​Materials  ●

x24​ ​Supplementary​ ​worksheet 

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x1​ ​Roll​ ​of​ ​sandpaper​ ​(for​ ​stripping) 

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x24​ ​Paper​ ​strips 

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x6​ ​Batteries​ ​(handful​ ​for​ ​testing) 

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x12​ ​Scissors 

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x24​ ​Audio​ ​plugs 

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x150​ ​Neodymium​ ​magnets 

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x6​ ​Soldering​ ​iron​ ​(PiE​ ​use​ ​only) 

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x6​ ​Tape​ ​rolls 

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x24​ ​Crayola​ ​Thick​ ​Markers 

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x2​ ​Wire​ ​spools​ ​(copper,​ ​32-gauge,  enameled) 

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x6​ ​Electromagnets​ ​(demo:  magnetism) 

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x24​ ​Bowl​ ​(foam​ ​or​ ​paper) 

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x12​ ​Nails/Staples​ ​(demo:  magnetism) 

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x48​ ​Manila​ ​folder​ ​strips 

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x2​ ​Half-finished​ ​product​ ​(demo:​ ​EM  to​ ​sound) 

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x24​ ​Cardboard​ ​(for​ ​the​ ​base) 

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x2​ ​Finished​ ​product​ ​(demo:​ ​EM​ ​to  sound) 

  Distribution​ ​of​ ​Materials​ ​per​ ​student 

  x1​ ​Supplementary  worksheet 

x5​ ​Neodymium​ ​magnets 

x1​ ​Cardboard 

x1​ ​Paper​ ​strip 

15’​ ​Wire 

x1​ ​Sandpaper​ ​strip 

1’​ ​Tape​ ​strip 

x1​ ​Bowl 

Battery 

x1​ ​Thick​ ​marker 

x2​ ​Manila​ ​folder​ ​strips 

x1​ ​Audio​ ​plug 

Scissors 

 

 

   

Introduction  Approximate​ ​time​ ​required​ ​(~15​ ​to​ ​20​ ​minutes)   

1.​ ​Electricity 

  What​ ​exactly​ ​is​ ​electricity?​ ​We​ ​hear​ ​this​ ​word​ ​all​ ​the​ ​time.​ ​Computers​ ​use​ ​electricity.  Power​ ​plants​ ​make​ ​electricity.​ ​The​ ​word​ ​is​ ​so​ ​prevalent​ ​in​ ​our​ ​lives​ ​now,​ ​that​ ​for​ ​many  of​ ​us,​ ​it’s​ ​one​ ​of​ ​life’s​ ​givens.​ ​We​ ​just​ ​don’t​ ​sit​ ​down​ ​and​ ​think,​ ​“what​ ​exactly​ ​is  electricity?”    Electricity​ ​is​ ​a​ ​flow​ ​of​ ​electrons​ ​(aka​ ​current)​ ​around​ ​a​ ​circuit​.    Demo​:​ ​Do​ ​the​ ​snap​ ​circuit​ ​demo.​ ​Explain​ ​how​ ​electricity​ ​will​ ​flow​ ​through​ ​the​ ​wires​ ​and 

power​ ​the​ ​lamp.​ ​How​ ​the​ ​battery​ ​provides​ ​the​ ​electric​ ​pressure​ ​to​ ​push​ ​the​ ​electrons  from​ ​one​ ​end​ ​of​ ​the​ ​battery​ ​to​ ​another.​ ​How​ ​if​ ​the​ ​circuit​ ​is​ ​broken,​ ​electricity​ ​won’t​ ​be  able​ ​to​ ​jump​ ​the​ ​gap.​ ​A​ ​highway/car​ ​analogy​ ​would​ ​be​ ​nice.    Hopefully​ ​you​ ​have​ ​a​ ​general​ ​idea;​ ​let’s​ ​start​ ​looking​ ​at​ ​the​ ​real​ ​thing.​ ​If​ ​we​ ​are​ ​going​ ​to  build​ ​an​ ​electric​ ​circuit​ ​from​ ​scratch,​ ​we​ ​will​ ​want​ ​to​ ​control​ ​where​ ​and​ ​which​ ​way​ ​it  flows.​ ​The​ ​wire​ ​is​ ​just​ ​like​ ​the​ ​riverbed​,​ ​it​ ​allows​ ​the​ ​electrons​ ​to​ ​flow​ ​through​ ​it.​ ​A  battery​ ​is​ ​just​ ​like​ ​a​ ​water​ ​pump​,​ ​it​ ​controls​ ​which​ ​direction​ ​the​ ​electrons​ ​will​ ​flow​ ​in.       2.​ ​Magnetism   Here’s​ ​another​ ​question.​ ​What​ ​exactly​ ​is​ ​magnetism?​ ​Many​ ​of​ ​our​ ​minds​ ​probably​ ​head  towards​ ​an​ ​image​ ​of​ ​a​ ​horseshoe​ ​magnet​ ​or​ ​maybe​ ​even​ ​of​ ​a​ ​bar​ ​magnet.​ ​All​ ​of​ ​these  magnets​ ​have​ ​a​ ​specific​ ​direction​ ​to​ ​them.​ ​These​ ​directions​ ​are​ ​called​ ​the​ ​north​ ​pole  and​ ​the​ ​south​ ​pole.​ ​Magnets​ ​will​ ​attract​ ​each​ ​other​ ​when​ ​opposite​ ​poles​ ​are​ ​nearby.  They​ ​will​ ​repel​ ​each​ ​other​ ​when​ ​similar​ ​poles​ ​are​ ​nearby.  Would​ ​you​ ​be​ ​shocked​ ​if​ ​I​ ​told​ ​you​ ​that​ ​we​ ​could​ ​make​ ​a​ ​magnet​ ​just​ ​like​ ​those  stuck​ ​on​ ​your​ ​refrigerator​ ​with​ ​clever​ ​use​ ​of​ ​electricity​ ​and​ ​wires?​ ​In​ ​fact,​ m ​ agnetism​ ​is  generated​ ​when​ ​current​ ​flows​ ​through​ ​a​ ​wire​!​ ​Most  of​ ​the​ ​time​ ​the​ ​magnetism​ ​is​ ​not​ ​noticeable,​ ​but​ ​if  we​ ​coiled​ ​a​ ​wire​ ​over​ ​and​ ​over​ ​like​ ​a​ ​spring,​ ​we​ ​can  make​ ​the​ ​magnet​ ​stronger.​ ​The​ ​magnetic​ ​effect  would​ ​be​ ​strong​ ​enough​ ​to​ ​affect​ ​other​ ​magnetic  material.​ ​This​ ​is​ ​the​ ​basics​ ​of​ ​an​ ​electromagnet!  So​ ​what​ ​makes​ ​an​ ​electromagnet​ ​so  special?​ ​For​ ​one,​ ​a​ ​regular​ ​magnet​ ​can’t​ ​be​ ​turned  on​ ​or​ ​off.​ ​You​ ​can’t​ ​tell​ ​it​ ​to​ ​attract​ ​that​ ​nail​ ​over  there,​ ​then​ ​tell​ ​it​ ​to​ ​not​ ​do​ ​it​ ​anymore.​ ​It’s​ ​going​ ​to  attract​ ​it​ ​whether​ ​you​ ​like​ ​it​ ​or​ ​not.​ ​An  electromagnet​ ​can​ ​be​ ​turned​ ​on​ ​or​ ​off.​ ​When​ ​a  current​ ​is​ ​flowing,​ ​it​ ​acts​ ​as​ ​a​ ​magnet.​ ​When​ ​a  current​ ​isn’t​ ​flowing,​ ​it​ ​doesn’t.​ ​An​ ​electromagnet  can​ ​change​ ​its​ ​strength​ ​depending​ ​on​ ​how​ ​strong  the​ ​current​ ​flowing​ ​through​ ​the​ ​wires​ ​is.​ ​A​ ​strong  current​ ​would​ ​make​ ​a​ ​strong​ ​magnet​ ​and​ ​a​ ​weak​ ​current​ ​would​ ​make​ ​a​ ​weak​ ​magnet.  Finally,​ ​and​ ​perhaps​ ​the​ ​most​ ​important​ ​part​ ​of​ ​an​ ​electromagnet,​ ​the​ ​north​ ​and​ ​south  poles​ ​of​ ​an​ ​electromagnet​ ​can​ ​change​ ​whenever​ ​you​ ​change​ ​the​ ​direction​ ​of​ ​the  current.​ ​When​ ​current​ ​is​ ​flowing​ ​one​ ​direction,​ ​it​ ​creates​ ​a​ ​magnet​ ​(say)​ ​with​ ​north​ ​on  top​ ​and​ ​south​ ​on​ ​bottom.​ ​However,​ ​if​ ​we​ ​flipped​ ​the​ ​direction​ ​of​ ​the​ ​current,​ ​it​ ​now 

creates​ ​a​ ​magnet​ ​(say)​ ​with​ ​south​ ​on​ ​top​ ​and​ ​north​ ​on​ ​bottom. 

  Procedure  1. Prepare​ ​enough​ ​tape​ ​for​ ​your​ ​speaker​ ​by​ ​taking​ ​about​ ​1​ ​foot​ ​of​ ​tape​ ​and​ ​putting  it​ ​aside. 

2. Grab​ ​1​ ​long​ ​(0.5​ ​x​ ​11​ ​inch)​ ​strip​ ​and​ ​a​ ​marker.​ ​Wrap  the​ ​strip​ ​around​ ​the​ ​marker​ ​to​ ​make​ ​a​ ​cylinder​ ​0.5  inch​ ​long.​ ​Cut​ ​some​ ​tape,​ ​and​ ​tape​ ​the​ ​paper​ ​so​ ​it  doesn’t​ ​unravel​ ​when​ ​you​ ​let​ ​go.​ P ​ icture​ ​to​ ​the​ ​right. 

3. Cut​ ​a​ ​wire​ ​~15​ ​feet​ ​in​ ​length.​ ​Leave​ ​~2​ ​feet​ ​of​ ​extra  wire​ ​before​ ​you​ ​start,​ ​then​ ​start​ ​coiling​ ​the​ ​wire  tightly​ ​around​ ​the​ ​paper​ ​cylinder​ ​at​ ​least​ ​50​ ​times.  You’ll​ ​want​ ​to​ ​try​ ​to​ ​coil​ ​the​ ​entire​ ​length​ ​of​ ​the  cylinder,​ ​but​ ​coil​ ​itself​ ​over​ ​so​ ​as​ ​to​ ​prevent​ ​it​ ​from  unwinding.​ ​Leave​ ​~2​ ​feet​ ​of​ ​extra​ ​wire​ ​on​ ​the​ ​other  end. 

4. Cut​ ​some​ ​tape,​ ​and​ ​tape​ ​the​ ​coil​ ​around​ ​the​ ​paper​ ​cylinder​ ​to​ ​hold​ ​it​ ​in​ ​place.  5. Tape​ t​ he​ ​paper​ ​cylinder​ ​to​ ​the​ ​bottom​ ​of​ ​bowl,​ ​as  close​ ​to​ ​the​ ​center​ ​as​ ​possible.​ ​Picture​ ​to​ ​the​ ​right. 

6. Take​ ​2​ ​Manila​ ​folder​ ​strips​ ​and​ ​fold​ ​them  hamburger​ ​style​ ​like​ ​a​ ​paper​ ​fan.​ ​Fold​ ​it​ ​one​ ​or​ ​two  more​ ​times​ ​so​ ​it​ ​resembles​ ​an​ ​accordion.​ ​Then  tape​ ​them​ ​onto​ ​the​ ​bottom​ ​of​ ​the​ ​bowl​ ​as​ ​parallel  and​ ​symmetrical​ ​as​ ​possible.​ ​Picture​ ​to​ ​the​ ​right. 

7. Tape​ ​a​ ​magnet​ ​to​ ​the​ ​middle​ ​of​ ​the​ ​cardboard  base.​ ​Stack​ ​the​ ​rest​ ​of​ ​the​ ​magnets​ ​on​ ​top​ ​so​ ​they  magnetically​ ​attach. 

8. Flip​ ​the​ ​bowl​ ​upright​ ​and​ ​fit​ ​the​ ​magnets​ ​in​ ​the  coiled​ ​cylinder. 

9. Fold,​ ​move,​ ​or​ ​cut​ ​the​ ​accordion​ ​strips​ ​so​ ​that​ ​the  bowl​ ​is​ ​balanced,​ ​is​ ​free​ ​to​ ​move,​ ​and​ ​has​ ​at​ ​least  half​ ​the​ ​magnets​ ​in​ ​the​ ​coiled​ ​cylinder. 

10.

Tape​ ​down​ ​the​ ​supports​ ​onto​ ​the​ ​cardboard  base.​ ​The​ ​plate​ ​should​ ​be​ ​parallel​ ​to​ ​the​ ​cardboard  base.​ ​Picture​ ​to​ ​the​ ​right. 

11.

Get​ ​a​ ​small​ ​piece​ ​of​ ​sandpaper,​ ​and​ ​strip​ ​about 

0.5”​ ​from​ ​each​ ​end​ ​of​ ​the​ ​wire.​ ​You​ ​can​ ​do​ ​this​ ​by​ ​gently​ ​sandwiching​ ​the​ ​wire  with​ ​the​ ​sandpaper​ ​and​ ​gently​ ​pulling​ ​the​ ​wire​ ​away.​ ​You’ll​ ​notice​ ​the​ ​red​ ​enamel  of​ ​the​ ​wire​ ​slowly​ ​disappear​ ​revealing​ ​the​ ​copper​ ​underneath. 

12.

Get​ ​a​ ​battery​ ​and​ ​test​ ​the​ ​speaker​ ​by​ ​touching  the​ ​loose​ ​ends​ ​of​ ​the​ ​wire​ ​to​ ​the​ ​ends​ ​of​ ​the  battery.​ ​The​ ​speaker​ ​should​ ​move.​ ​If​ ​it​ ​doesn’t  then​ ​try​ ​removing​ ​more​ ​enamel​ ​from​ ​the​ ​wire​ ​or  loosening​ ​the​ ​cylinder​ ​from​ ​the​ ​magnets. 

13.

Thread​ ​the​ ​two​ ​loose​ ​ends​ ​of​ ​the​ ​wire​ ​through  the​ ​audio​ ​plug​ ​sheath.​ ​Then​ ​fit​ ​the​ ​wire​ ​into​ ​the  audio​ ​plug​ ​holes.​ ​With​ ​the​ ​help​ ​of​ ​PiE​ ​staff,​ ​solder  the​ ​ends​ ​to​ ​an​ ​audio​ ​connector.​ ​Picture​ ​to​ ​the  right. 

14.

Test​ ​it​ ​out​ ​with​ ​your​ ​mp3​ ​player​ ​or​ ​audio​ ​device​ ​by​ ​plugging​ ​the​ ​aux​ ​jack​ ​into  the​ ​audio​ ​plug! 

     

Discussion  1.​ ​Sound  You’ve​ ​just​ ​built​ ​a​ ​speaker,​ ​so​ ​it’s​ ​important​ ​to​ ​know​ ​what​ ​sound​ ​is​ ​and​ ​how​ ​it​ ​works.    Sound​ ​is​ ​the​ ​compression​ ​and​ ​expansion​ ​of​ ​a​ ​medium​ ​like​ ​water​ ​or​ ​air.​ ​When​ ​you​ ​listen  to​ ​someone​ ​talk​ ​or​ ​sing,​ ​the​ ​person’s​ ​vocal​ ​cords​ ​vibrate,​ ​manipulating​ ​the​ ​flow​ ​of​ ​air.  The​ ​same​ ​occurs​ ​when​ ​an​ ​instrument​ ​is​ ​played.​ ​The​ ​instrument’s​ ​material,​ ​like​ ​a​ ​drum  head,​ ​vibrates,​ ​compressing​ ​air.​ ​When​ ​the​ ​air​ ​gets​ ​to​ ​your​ ​ear,​ ​your​ ​ear​ ​has​ ​special  equipment​ ​that​ ​allows​ ​it​ ​to​ ​translate​ ​the​ ​rate​ ​at​ ​which​ ​these​ ​compressed​ ​air​ ​molecules  arrive.​ ​If​ ​the​ ​drum​ ​head​ ​is​ ​vibrating​ ​quickly/slowly,​ ​compressing​ ​the​ ​air​ ​at​ ​a​ ​quick/slow  rate,​ ​it​ ​is​ ​associated​ ​with​ ​a​ ​high/low​ ​pitch. 

​​

Image​ ​source:​ ​http://www.mediacollege.com/ 

 

EM​ ​to​ ​Sound  Finally!​ ​How​ ​does​ ​this​ ​all​ ​connect​ ​with​ ​each​ ​other?​ ​Let’s​ ​think​ ​about​ ​this​ ​like​ ​an  engineer!  The​ ​electromagnet​ ​is​ ​taped​ ​to​ ​the​ ​bowl.​ ​When​ ​current​ ​flows​ ​through​ ​the 

electromagnet,​ ​it​ ​acts​ ​just​ ​like​ ​a​ ​regular​ ​magnet.​ ​As​ ​the​ ​electromagnet​ ​turns​ ​on,​ ​turns  off,​ ​or​ ​switches​ ​direction,​ ​it​ ​is​ ​attracted​ ​or​ ​repelled​ ​to​ ​the​ ​magnet​ ​taped​ ​to​ ​the​ ​cardboard  base.​ ​(When​ ​you​ ​use​ ​the​ ​speaker,​ ​can​ ​you​ ​see​ ​the​ ​oscillations?)​ ​This​ ​results​ ​in​ ​the  oscillation​ ​of​ ​the​ ​bowl,​ ​the​ ​compression​ ​of​ ​air,​ ​and​ ​thus​ ​sound​ ​is​ ​made. 

   

 

Extra​ ​time:   1. What​ ​genre​ ​of​ ​music​ ​does​ ​your​ ​speaker​ ​play​ ​the​ ​best?​ ​Classical,​ ​rock,​ ​electronic,  pop,​ ​or​ ​hip​ ​hop?​ ​How​ ​about​ ​artists?​ ​Beethoven,​ ​AC/DC,​ ​Daft​ ​Punk,​ ​Rihanna,​ ​or  Jay-Z?​ ​Try​ ​putting​ ​on​ ​your​ ​scientist​ ​cap​ ​on,​ ​make​ ​a​ ​list,​ ​and​ ​rate​ ​them​ ​1-10.  2. What​ ​do​ ​you​ ​think​ ​would​ ​happen​ ​if​ ​you​ ​changed​ ​some​ ​of​ ​the​ ​materials?​ ​What​ ​if  you​ ​used​ ​less​ ​magnets?​ ​More​ ​magnets?​ ​Less​ ​loops​ ​of​ ​wire?​ ​More​ ​loops?​ ​Do​ ​you  think​ ​paper​ ​or​ ​styrofoam​ ​is​ ​better?​ ​What​ ​about​ ​a​ ​plate​ ​instead​ ​of​ ​a​ ​bowl?​ ​We  encourage​ ​you​ ​to​ ​think​ ​about​ ​all​ ​these​ ​things,​ ​come​ ​up​ ​with​ ​a​ ​hypothesis,​ ​and  even​ ​test​ ​it​ ​out!​ ​The​ ​instructions​ ​to​ ​build​ ​the​ ​speaker​ ​will​ ​be​ ​the​ ​same,​ ​just  change​ ​that​ ​little​ ​bit​ ​you​ ​want​ ​to​ ​test.  3. These​ ​speakers​ ​also​ ​work​ ​as​ ​microphones.​ ​If​ ​you​ ​plug​ ​it​ ​into​ ​a​ ​computer’s  microphone​ ​port​ ​and​ ​use​ ​a​ ​sound​ ​recording​ ​program​ ​like​ ​Audacity,​ ​you​ ​can​ ​get​ ​a  decent​ ​recording​ ​of​ ​yourself​ ​if​ ​you​ ​talk​ ​loudly​ ​into​ ​the​ ​speaker.​ ​Try​ ​it​ ​out!​ ​Why​ ​do  you​ ​think​ ​this​ ​works?​ ​(Hint:​ ​Think​ ​of​ ​EM​ ​to​ ​Sound)  4. Now​ ​we’ve​ ​learned​ ​how​ ​speakers​ ​work.​ ​All​ ​it​ ​took​ ​was​ ​learning​ ​seemingly  unrelated​ ​scientific​ ​subjects​ ​and​ ​applying​ ​them​ ​together.​ ​We​ ​encourage​ ​you​ ​to  look​ ​at​ ​more​ ​things​ ​taken​ ​for​ ​granted​ ​like​ ​a​ ​clock​ ​and​ ​learn​ ​what​ ​makes​ ​it​ ​tick.  Soon​ ​enough,​ ​you’ll​ ​find​ ​science​ ​everywhere!     

References  http://www.josepino.com/?homemade-hifi-speaker