getting current: generating electricity using a...

8 E N E R G Y F O R K E E P S : E L E C T R I C I T Y F R O M R E N E W A B L E E N E R G Y

Materials for Warm-up (Optional)

Iron filings

Stiff paper

Strong bar magnet

Materials for Student Activity

Per student group:

Student handout: “Getting Current”

Copy of Chapter 2 Discussion,Energy and Electricity

A directional compass

A strong bar magnet with northand south poles

13 feet (4 m) insulated copperwire

Cardboard toilet paper tube

Transparent tape (optional)

At least one for the entire class:

Wire stripper/cutter

Teaching NotesEnsure that students understandthat the activity setup is just ademonstration of the idea thatmoving a conductive wire in amagnetic field can create anelectrical current. The setup inthis activity does not look like a power plant generator, butboth use coiled wire and strongmagnets. The model works usingthe same principle.

Remind students to keepmagnets away from computerdisks, audio or video tapes, etc.

P L A N N I N G O V E R V I E W

SUBJECT AREAS:Physical Science, Math, LanguageArts

TIMING:Preparation: 30 minutesActivity: 1-2 45-minute class periods

SummaryStudents investigate how gener-ators produce electricity by usingelectromagnetism.

GETTING CURRENT:Generating Electricity Using a Magnet

Model generator

ObjectivesStudents will:� Hypothesize what will happen

and why when a bar magnet ispassed in various ways throughcoils of wire.

� Construct and use a model thatdemonstrates the actions of anelectricity generator.

� Prepare a brief summary of theactivity, including a descriptionof the set-up and whatoccurred when it was tested.

� Draw a conclusion comparingtheir hypotheses to what wasobserved in the activity.

� Compare their models to anactual electricity generator.

� Propose explanations relatingmagnetism and electricity.

� Recognize that the main reasonfor making an electrical turbinespin is to turn a generator.

� Compare both models to anactual power plant turbine and generator(if “Going for a Spin”was also done).

24" (60 cm)

Bar magnet

9E N E R G Y F O R K E E P S : E L E C T R I C I T Y F R O M R E N E W A B L E E N E R G Y

Iron filings showing magnetic fields

Since this activity is a simpledemonstration, the full scientificmethod outline is not called forhere. Rather, certain key elementsof the method are used, includinghypothesizing, describing theactivity, gathering data, anddrawing conclusions.

If students have trouble withtheir models, have them try making more coils. If this doesn’tproduce an electric current (movethe compass dial), you may needstronger magnets.

Items in the materials list canbe found at hardware, electronics,or school supply stores. You canalso order them from a sciencesupplier such as Sargent-Welch,Edmund Scientific, or NascoScience. If you can’t find iron filings, show the magnetic fieldillustration (also in the studenthandout) to your students.Discuss it using information inthe Warm-up section, or havestudents view a video or CD-ROMthat discusses magnetic fields.

Warm-up (Optional)If you were able to find someiron filings, try this with yourstudents: Place a stiff piece ofpaper over a bar magnet that isresting on a flat surface. Sprinklesome iron filings on the piece ofpaper. Ask students to observewhat happens. The interestingpattern that results is due to the magnetic field surroundingthe magnet.

Explain that any magneticfield is actually invisible to us.The iron filings are lining up inreaction to the magnetic field,and show the lines of magneticforce — the “attraction” thatoccurs between the two oppositepoles (north and south) of themagnet. The lines of force in amagnetic field travel from northto south — much the same wayelectric current flows from nega-tive to positive (opposite chargesattract).

In this activity, the magneticfield of the bar magnet interacts

with electrons in a wire to createan electrical current.

Note: Students may ask whatcauses magnetism in the firstplace. Tell students that untilrecently, the cause of magnetismwas not well understood. In fact,not long ago, the EncyclopediaBritannica stated: “Few subjectsin science are more difficult tounderstand than magnetism.”Recently scientists have begun to unlock magnetism’s mysteries,but the answers are very complex, having to do with “spin”of electrons on their own axis asthey buzz around the nucleus ofan atom.

The Activity1. Gather the necessary materials

and set up your classroom toaccommodate the activity.Refer to the Student Activitypage for the specific procedure.

2. Use the Chapter 2 Discussionto talk about how a powerplant generator works. Usingthe graphic of the typicalsteam-driven power plant on page 13, discuss how thepower plant turbine providesthe spinning force that turnsthe generator. While this diagram does not show theinner workings of the generator,it does illustrate the intercon-nection of the turbine and thegenerator.


3. Next direct the students’attention to illustration, “Insidea turbine generator” (also inthe student handout). Explainthat in generators the rapidspinning of wire coils betweenthe two poles of strong magnetsproduces an electrical current.

4. Point out that in most powerplant turbines the wire coilsare moving and the magnetsare stationary. However, it canwork the other way around.We can move a magnet in andout of wire coils (as demon-strated in this activity) and stillgenerate an electric current.

5. Review with the class the outline they must prepare towrite-up the activity. The

specific directions for doing soare found in the StudentHandout for this activity. Tellstudents that they will beworking in groups to do theactivity, but each will do hisor her own write-up.

6. Organize students into groups.Pass out materials and copiesof the Student Activity pages.

7. Have students look over theactivity directions, then reflecton what they’ve learned so farabout generators and electro-magnetism. Then ask them tofill in the Hypothesis portion of their outline (see page 13).Explain that they need to predict what they think willhappen when they do theactivity and why.

8. Have students create and testtheir own model generators.Allow time for them to also dotheir activity write-ups.Remind them that the back-ground information they needto help explain how theirexperiment works was includedin your discussion of thisactivity, and is also found bothin the Chapter 2 Discussion, as well as in their studenthandout, “Getting Current.”

Electricity

Magnets

Coiled copper wire

Steam outlet

Turbineblades

Steam entry

Inside a turbine generator


9. Have the class get togetherafter groups have tested theirmodel generators and havedone their write-ups. Ask students to use what they’velearned from studying Chapter 2and their experiences withboth activities to write a briefnarrative, on separate paper,comparing both the turbinemodel and the generatormodel to an actual powerplant turbine and generator. Ifyou did do “Going for a Spin,”then have students explainhow their generator modelcompares to an actual powerplant generator.

Wrap-upCall the class together to discusstheir findings. Ask students toexplain why they think genera-tors work the way they do.

Ensure that students are ableto make the connection betweenelectricity and magnetism andhave a general understanding ofelectromagnetism.

Next conduct a discussionconnecting this activity (and thatof “Going for a Spin” if you havedone it as well) to an actualpower plant that uses turbinesand generators.

Referring back to the Warm-up, remind students that magnetscreate a magnetic field aroundthem. This field causes electronsto move in the conductive wiresthat are spun inside the magneticfield. If these wires are connectedin a complete pathway, or circuit,an electric current will thencourse through the wires.

Explain that the compass intheir activity set-up serves as a“galvanometer,” a device thatindicates electric current. Thevery small current produced bythe passing of the magnetthrough the coils of wire causesthe compass needle (which ismagnetized) to turn aside, ordeflect. This is a property of electromagnetism.

ExtensionAs a follow-up, students mayalso wish to look up power plantgenerators in reference books oron the Internet to learn moreabout how they work. Otherinteresting topics to pursue arethe electromagnetic force andthe history of the compass (thisone may appeal to both historyand science buffs alike).

Permission was granted by the TennesseeValley Authority to adapt portions of theirjunior high curriculum unit, “The EnergySourcebook” for use in this activity.

Assessment Students will have had theopportunity to:� Create and test a model

generator.� Prepare a write-up of the

activity, including usinghypothesis, description, andconclusion.

� Develop an activity write-upthat includes diagrams andlabels and tells why the activityworked the way it did basedon what they have learnedabout electricity and magnetism.

� Produce a brief narrativedescription comparing an actual power plant generator to their turbine models from thefirst activity and their generatormodels from the second activity.


GETTING CURRENT:Generating Electricity Using a Magnet

Generators use magnets andwire coils to produce elec-

tricity. The electricity is producedby the rapid rotation of wire coilsbetween the two poles of strongmagnets (or the spinning of mag-nets surrounded by wire coils).Turbines — driven by a forcesuch as pressurized steam, mov-ing water, or forceful wind —provide the spinning power.

Magnets are surrounded by amagnetic field that can causeelectrons to move in wires turn-ing inside this field. If thesewires are conductive (allowingelectrons to flow easily), and if

they are connected in a completepathway (called a circuit), anelectric current will then runthrough those wires.

While most generators operateby rapidly turning wire coilsinside the two poles of a magnet,it also works the other wayaround — we can move a magnetin and out of wire coils to gener-ate an electric current. In thisactivity, you will demonstratethis concept using a compass(which has a magnetized pointerthat acts as a current detector) toshow that electricity has beenproduced.

MaterialsPer student group:� A compass� A strong bar magnet with north

and south poles� 13 feet (4 m) insulated copper

wire� Cardboard toilet paper tube� Transparent tape (optional)

At least one for the entire class: � Wire stripper/cutter

Electricity

Magnets

Coiled copper wire

Steam outlet

Turbineblades

Steam entry

Inside a turbine generator


Next, review what you havelearned so far about generatorsand electromagnetism, and studythe directions for the activity.Based on this information, pose ahypothesis predicting how youthink the generator model willwork and why.

When everyone in your grouphas completed his or her hypoth-esis, move on to the Procedure.

Procedure 1. Remove about 3⁄4 inch (2 cm) of

insulation from each end ofthe wire.

2. Wrap one end of the wirearound the compass five timesas shown. Be sure to positionthe compass so that the needleis directly underneath thewire wrapped around it. CAUTION: Ends of wire aresharp.

3. Extend the other end of thewire out about 24 inches(about 60 cm) from the compass and then wind theremaining length around thecardboard tube five times. Thebar magnet will pass throughthese coils.

4. Run the remainder of the wireback to the compass. Twist thetwo exposed ends of the wiretogether. If desired, secure thewire to the compass withtransparent tape.

5. Have one group member passthe magnet back and forththrough the coils. If nothinghappens disconnect one sideof the wire and add more coilsto the tube, then reconnect.Keep the compass at least 20 inches (50 cm) from themagnet so that the magnetitself does not cause the needleof the compass to be deflected.

24" (60 cm)

Bar magnet

Model generator

Prepare Write-up OutlineMake an outline, leaving room towrite in each section, using theformat below. Be sure to titleyour paper and include name,group name or number, and date.

1. Hypothesis. Predict what willhappen.

2. Activity Description/Data.Describe the set-up and whathappened when you tried all thevariations suggested.

3. Conclusion. Revisit yourhypothesis. Tell whether or not itwas correct, and why.


UNLOCKING SOME OF MAGNETISM’S MYSTERIES

Although we can’t see magnetism, we’ve all

seen its effects. We know thatmagnets have a force that canattract certain materials (oranother magnet). The force of amagnet can also cause anothermagnet to move away. We usemagnetic forces everyday, fromrefrigerator magnets holding upmemos to magnetic poles incommon devices such as motorsand telephones.

Most of us are also familiarwith the terms north pole andsouth pole. This is somethingyou usually can find marked on a bar magnet. (The labels northand south pole are arbitrarynames given by scientists whofirst studied magnetism.) Allmagnets have north and southpoles — no matter what shape

they are. Magnets have the mostforce at the poles. However,magnetic lines of force actuallyextend all around the magnet,creating a magnetic field.

Scientists are still exploringwhat causes these lines of magnetic force. They do knowthat most atoms actually act likemicroscopic magnets, each with its own tiny north andsouth pole. When atoms are alljumbled up — as they are inmost materials — we don’t noticethe atoms’ magnetic force. But,in certain materials (mostly some metals), the atoms all line up,creating a collective north poleat one end and a south pole at the other. This results in magnetism at each pole strongenough to attract a material such as iron.

6. Other group members shouldwatch the compass closely to observe and record whathappens.

7. Change the direction of themagnet by inserting it from theopposite end of the tube.Observe and record what happens. Next turn the magnet around (inserting the other pole first). Observeand record what happens.

8. Stay in your groups to finishwriting up your activity. Groupmembers should share insightsand give each other support,but each person should writehis or her own.

Include your three observa-tions based on the three different ways you tested themodel. Using the Chapter 2Discussion, your classroominstruction, and the informa-tion on this worksheet, explain why the compassreacted the way it did in your conclusion.

9. Be prepared to discuss yourfindings with the class.

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