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BELL, BUZZER

& SWITCH65168-05

STUDENTS WORKBOOKBy Lawrence F. Lowery

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MATERIALS INCLUDED IN THIS KIT

1 Bell 5 Pegs + Round Holder +1 Bobbin 1 Cap (on plastic bar)1 Switch Base 1 Clapper 1 Circuit Base 1 Sounder 1 Back Panel 1 Battery

You will find all items in the following groupings packaged together insmall plastic bags within your kit.

1 Compass Base 1 Adjuster Screw 1 Compass Needle 1 Adjuster Nut 3 Nails 1 Washer for Adjuster Nut 1 Metal Tool 1 Spring1 Metal shaft for bobbin 2 Battery Clips

1 Small Screw + Nut1 Piece Sandpaper 1 Medium Screw + Nut 1 Wire Coil

1 Key Contact1 Bobbin Bracket1 Switch Key

SOUNDERCOMPASS

BASE

COMPASS NEEDLE

3 NAILS

CLAPPER

WIRE

BOBBIN

METALSHAFT

BELL

CIRCUIT BASE BACK PANEL

BATTERY

+ 5 PEGS

SWITCHKEY

SCREW& NUT

CAP

TOOL

KEYCONTACT

SANDPAPER

SPRINGROUNDHOLDERADJUSTER

NUT

ADJUSTERSCREW

WASHER FORADJUSTER NUT

SWITCH BASE

BATTERY CLIPS

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STUDENTS WORKBOOKBELL, BUZZER & SWITCH KIT

INTRODUCTION

What would happen if suddenly there was

no electricity? Radios, television, telephonesand stereos would be silent and blank Homeswould be dark. Cars wouldnt run. Airplaneswouldnt fly. In short, your life would be verydifferent if you had no electricity in your home.

One of the most important properties ofelectricity is that it produces a magnetic force.This force can be harnessed to power thou-sands of devices that we have come to rely on

in our daily lives.The materials in this Bell, Buzzer, andSwitch Kit can be used to build several smalldevices that are run by electricity and magnet-ism. These devices will show you how manyother machines and tools work. Before youbegin the four Explorations on electricity andmagnetism, check the list of materials on thepreceding page to make sure your Discovery

Kit is complete.CIRCUIT ASSEMBLY

In this exercise you will build an electricalcircuit to use in all of the Explorations in this kit.Assembling the circuit is done in three parts:Preparing the Bobbin, Building the Switch, andCompleting the Circuit.

PREPARING THE BOBBIN:To start, find all the pieces noted in List A andprepare the bobbin and wires as follows:

1. Use scissors to cut about one foot of wirefrom the wire coil. Set the piece of wireaside to use when Building The Switch.

2. Starting from the center of the bobbin,thread about 6 inches of wire from theend of the remaining coil through the

small hole on one side of the bobbin. Putthe end of the wire through the hole againto form a loop (see pictures A & B). Pullthe loop tight to hold the end of the wirefirmly in place.

3. Begin to unwind the rest of the coil andstart wrapping the wire evenly around thebobbin (pictures C & D). To keep the wire

1

LIST A

Wire CoilBobbinSandpaper

A.

B.

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from tangling, you might want to hold theloop of coil over your thumb or finger,straightening it out as you use it. When youreach one edge of the bobbin, begin wrap-ping the wire towards the other edge. Keep

the wire tight on the bobbin and free ofkinks. When winding, make sure that thewires do not cross one another, and thatthe loops are close together and parallel toone another. Keep winding until there isabout 6 inches of wire left. TAKE YOURTIME ON THIS STEP. A PROPERLYPREPARED COIL IS THE MOSTIMPORTANT ELEMENT OF THIS KIT.

4. Starting from inside the bobbin, thread thelast 6 inches of wire through the small hole onthe other side of the bobbin. Loop it throughthe hole, taking care not to kink the wire.

5. Use the sandpaper to rub away 1 inch ofthe coating from both ends of the bobbinwire (picture E). The ends of the wire shouldbe a bright copper color when you finish.

6. Set the prepared bobbin aside, to use

when completing the circuit.

BUILDING THE SWITCH:Next, find the pieces noted in List B, and

build the switch as follows:1. Slip the key contact into one side of the

base. Make sure that the hole on the keycontact matches up with the hole on theswitch base. Using the metal tool (or a

small slot head screwdriver), bend the lock-ing tabs underneath the base to hold thekey contact in place.

2. Cut the piece of wire you set aside earlier(Step 1: Building The Switch) in half. Usesandpaper to rub away 1 inch of the coat-ing from both ends of both pieces of wire.Set one piece of wire aside. You will use itlater in Exploration 3.

3. Remove the round holder from the plasticbar. Place the remaining wire into the notchon the holder, leaving about one inch stick-ing out on one side. With the wire in place,push the round holder firmly into the holeon the key contact. The wire should now beheld securely in place (see picture F).

2

LIST B

Switch BaseKey ContactMetal ToolSwitch KeySandpaper

Round HolderCap(the Round Holder and Capare on the plastic bar)

C.

C.

E.

F.

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4. Find the switch key and the cap. Use themetal tool to bend the tab at the end of thekey up. Put the cap on the tab. (You mightwant to place a drop of glue on the inside

of the cap before you put it on the tab).5. Insert the switch key into the remainingslots of the switch base, so that when youpress the tab at the end of the key, it touch-es the top of the round holder. Use themetal tool to bend the locking tabs under-neath the base to hold the key in place.When you press the switch key down,make sure that it touches the raised metal

circle of the key contact (see picture G).COMPLETING THE CIRCUIT:

Now, find the pieces noted in List C, andcomplete the circuit as follows:

1. Put the battery clips into the slots in the cir-cuit base. Bend back each set of lockingtabs underneath the base to hold the clips

in place.2. Remove two pegs from the plastic bar. Eachpeg has a small hole in it. Thread about 1inch of a free end of the bobbin wirethrough the hole in one peg (see picture H).Wrap the free end of the wire around thebase of the peg, and insert the peg into thehole in the battery clip (see picture I).

LIST C

Circuit BaseBattery ClipsPegsMetal ToolPrepared Bobbin6 Piece of WireAssembled

Switch(see picture G)AA Battery

G.

H.

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3. Thread about 1 inch of the remaining freeend of the bobbin wire through the hole inanother peg. Again, wrap the wire aroundthe base of the peg. Insert this peg into the

hole on the switch (see picture J).4.Thread the wire extend-ing from the roundholder on the switchthrough another peg.Wrap about 1 inch ofthe wire around thebase of the peg. Insertthis peg into the remain-

ing battery clip on thecircuit base.5. Place the battery in the slot between the

battery clips.6. Insert the metal bobbin shaft into the bob-

bin (see picture K).

You should now have an open cir-cuit like the one shown in picture J.

Trace the circuit with you finger. Where is thebreak in circuit? How would you close it?

EXPLORATION 1:TESTING THE ELECTROMAGNET

Assemble the materials noted in List D forthis Exploration.

The battery in the circuit you have createdprovides the electricity for the circuit. That elec-

tricity, however, will not travel through the coilof wire until the circuit is closed.Close the circuit by pressing down the

switch key. Hold the nail against the metalbobbin shaft. What happens? Lift you fingerfrom the switch key to break the circuit. Whathappens to the nail now?

Closing the circuit carries the current fromthe battery to the coil around the bobbin. This

current carrying coil acts like a magnet, and iscalled an electromagnet. The magnetic forcecarried by the electromagnet holds the nailagainst the shaft when the circuit is complete.

LIST D

Open Circuit(see picture J)NailCompass NeedleCompass Base

J.

K.

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You can test the strength of your electromagnetseveral different ways. First, hold some paper clipsnear the circuits coil. How many paper clips does theelectromagnet attract? How close do paper clips need

to be from the coil before they are attracted to it?You can also test your electromagnet with a com-pass. To build your compass, insert a nail throughthe indentation in the compass base. Set the base ona flat surface. Place the compass needle on the endof the nail. Watch the compass needle. Whichdirection does the red tip of the compass point?

Now press the switch and slowly bring the elec-tromagnet near the compass. What happens to the

compass needle? Release the switch. What happensto the compass needle now?Remove the battery from the circuit base and

turn it around, so that the terminals are reversed. Putthe battery back in the base.

Press the switch again. Now what happens tothe compass needle? Can you make any observa-tions about the way an electrical current flowsthrough the circuit from this?

EXPLORATION 2: MAKING A SOUNDERAssemble the materials noted in List E for this

Exploration.Using your electromagnet, you can make a

device that is similar to a telegraph.Construct the sounder as follows:

1. Make sure that the metal bobbinshaft is inside the bobbin. Insert the

two tabs on the bobbin into the slotson the back panel. You may need tosqueeze both ends of the bobbinbetween your thumb and finger to fitit into the tabs. Make sure that thetop of the shaft is towards the top ofthe panel (see picture L).

2. Attach the bobbin bracket to thebobbin. The bottom of the bobbin

shaft should fit into the hole in thebobbin bracket. Match the smallerhole on the bracket to the small holein the back panel. Fasten the brack-et onto the panel with a screw andnut (picture M).

LIST E

Open Circuit(see picture J)Bobbin BracketBack PanelScrew and NutSounder

L.

M.

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3. Slide the entire back panel unit intothe appropriate slot on the circuitbase (picture N).

4. Place the sounder on the base (pic-

ture O). The sounder should go inbetween the top of the bobbin andthe top of the back panel; it shouldnot, however, touch the top of thebobbin shaft. If it does, bend thecopper base of the sounder. If it stilltouches the top of the bobbin shaft,try pushing the shaft further intothe bobbin. Also try bending down

the tab at the end of the sounder(by the peg hole). Onceit is properly positioned,fasten the sounder inplace with a peg.

Now you have createdan extended circuit like theone in picture P. Trace the

circuit with your finger.In Exploration 1, youlearned that your electro-magnet is a temporarymagnet: that is, it can beturned on and off by press-ing or releasing a switch toopen or close a circuit.

Press the switch cap in

the circuit you have created.What happens to thesounder? Now release theswitch. What happens?

Rapidly press andrelease the switch cap. Youshould hear a rapid clickingsound as the sounder ispulled to and from the top

of the bobbin shaft.The electric device youhave just created is much like a telegraph key andsounder. It is possible to send messages with thisdevice, through a code of short and long clicks,known as dots and dashes, which translate intoletters of the alphabet.

6

O.

P.

N.

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A dot is made by quickly pressing andreleasing the switch key. A dash is made bypressing and releasing the key more slowly. Adash should be as long as three dots. Thiscode, which has been used to send messagesaround the world, is known as theInternational Morse Code.

The letter translations of the InternationalMorse Code are as follows:

Practice sending code messages with yourdevice. You and a friend can send messagesto each other this way.

EXPLORATION 3: MAKING A BUZZERAssemble the materials noted in List F for

this Exploration.Using your electromagnet, you can alsomake an electric-powered buzzer.

Construct the buzzer as follows:1. Slip the adjuster nut between the clips at

the top of the back panel (picture Q).Place the small spring on theadjuster screw and turn thescrew into the adjuster nut.Turn the screw until it barelytouches the round metal diskon the coppersounder (pictureR). As in Exploration 2, it maybe necessary to adjust the posi-tion of the sounder to completethis connection.

A B C D E F G H I.- -... -.-. -.. . ..-. --. .... ..

J K L M N O P Q R

.--- -.- .-.. -- -. --- .--. --.- .-.S T U V W X Y Z... - ..- ...- .-- -..- -.-- --..

1 2 3 4 5 6 7 8.---- ..--- ...-- ....- ..... -.... --... ---..

9 10----. ----- LIST F

Sounder Circuit(see picture P)Adjuster NutAdjuster ScrewSpringReserved Wire(from Step 2,

Building the Switch)

R.

Q.

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2. Change the wire connections in the circuitas follows:

Currently ChangeWire extending from top of Remove peg from battery

bobbin connects to peg in holder; unloop wire from pegbattery holder. and set peg aside. Loop andknot wire through small hole onextending tab of adjuster nut.

Wire extending from bottom of Remove peg and wire frombobbin connects to peg in base of switch; insert into openbase of switch. battery holder.

3. Loop one end of the wire you preparedearlier through the small hole in one ofthe pegs; wrap the wire around the baseof the peg. Place the peg into the hole onthe switch. Loop and knot the other end ofthe wire through the tab at the end of thesounder (by the peg hole).

By now, your circuit

should look like theone in picture S. Tracethis extended circuitwith your finger.

Now, press theswitch and hold itdown. Does thesounder buzz? If not,turn the adjuster screw

up or down until thesounder buzzes. Besure the lower part ofthe sounder does nottouch the metal shaftwhen the switch is off.

Watch the sounderas it buzzes. How is magnetism used to makeit work? Why doesnt the sounder stick to the

magnet all this time? Can you send code sig-nals with your buzzer?

S.

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EXPLORATION 4:MAKING AN ELECTRIC BELL

Assemble the materials noted in List G forthis Exploration.

Using your electromagnet, you can also

make an electric-powered bell, similar to thedoorbell in your home.Construct the electric bell as follows:1. Remove the sounder arm from its base

and replace it with the bell clapper. Fastenthe clapper in place with the peg from thesounder arm. Make sure that the bottomof the bell clapper does not touch the topof the bobbin shaft. If necessary, adjustthe position of the clapper as you did with

the sounder in Exploration2.2. Remove the wire from the sounder arm;

loop and knot it around the tab extendingfrom the clapper arm.

3. Mount the bell on the back panel with thescrew and a nut. Insert your finger in theopening in the back panel to hold the nutin place while tightening the screw.Tighten the screw with either the metal tool

or a small screwdriver.

The circuit for your electricbell should look like the onein picture T. Trace this extend-ed circuit with your finger todouble check that all connec-tions are secure. How do youthink magnetism will be used

this time?Press the switch key: Thebell should ring. If it doesnt:a) Check your connections. Make

sure they are tight.b) Make sure the metal clapper

isnt touching the bobbinwhen the switch is open.

c) Turn the adjuster screw up or down against the clapper arm.d) Check your battery to see if it is still good.e) Bend the metal clapper closer to or further away from the bell.

Using longer wires, how could you and a friend set up yourbells so your switch would ring your friends bell, and his switchwould ring yours? Do you think it is possible to send messagesby ringing the bells?

Turn the battery around so that the position of the positiveand negative terminals are reversed. Now try the switch. Doesthe bell still sound? It should, since the current flows in bothdirections.

LIST G

Sounder Circuit(see picture S)Bell Clapper

BellScrew and NutMetal Tool

T.

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Dr. Lawrence F. Lowery is a professor of science education at theUniversity of California, Berkeley. He has had extensive elementaryand junior high school teaching experience, has written numerousfilms and books on science and has written many articles for teacherson science instruction.

THIS DISCOVERY KIT IS ONE IN A SERIES COVERING BASICSCIENCE CURRICULUM OTHER KITS ARE AVAILABLE FOR

TEACHING SOUND, MAGNETISM, LIGHT, FRICTION,ELECTROLYSIS, WEIGHTS AND MEASURING, AND SIMPLEMACHINES AND BALANCE.

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