Mag Electromag

8/8/2019 Mag Electromag

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Magnetism and Electromagnetism

ional Aeronautics and Space Administration

M a g n e t i s m a n

d E l e c

t r o m a g n e

t i s m


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Tis teachers guide is designed to support a multi-year investigation o Earths magnetic eld using themagnetometer network and resources o NASAs HEMIS ( ime History o Events and Macroscale In-teractions during Substorms) satellite mission education program. Te education programs website canbe ound at http://ds9.ssl.berkeley.edu/themis/. One particular HEMIS education program, theGeomagnetic Event Observation Network by Students (GEONS), aims to bring magnetometer data tohigh school classrooms. Tese guides support that e ort.

Te activities were designed in partnership with the IMAGE (Imager or Magnetopause-to-Aurora Glob-al Exploration) satellites education program (http://image.gs c.nasa.gov/poetry) and the many activitiesdeveloped or that mission in the exploration o the magnetosphere. Te FAS (Fast Auroral Snapshot)education program also contributed to this e ort (http://cse.ssl.berkeley.edu/ ast_epo).

Authors:

Dr. Sten Odenwald - HEMIS E/PO (education and public outreach) Specialist at Astronomy Ca

Dr. Laura Peticolas - Co-Director, HEMIS E/PO

Dr. Nahide Craig - Director, HEMIS E/PO

erry Parent - Middle school science teacher in Carson City, NV

Cris DeWol - High school science teacher in Remus, MI

eacher input and testing:

Laura Barber, Wendy Esch, Sean Estill, Wendell Gehman, Keith Little, Victor rautman,

and Holly WyllieScientist/Engineer input and testing:

Dr. Vassilis Angelopoulos - HEMIS Principal Investigator (PI)

Dr. Chris Russell - E/PO Science Advisor

Layout/Editorial assistance:

Karin Hauck


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Contents

National Science Education Standards ........................................................................................v

Nation Math Education Standards ............................................................................................ vi

Introduction .............................................................................................................................. vii

Activity 1: Permanent Bar Magnets ............................................................................................ 1 Work with common magnets to re-discover the basic properties o magnets polarity,

attraction, repulsion, feld lines.

Activity 2: Electromagnets ......................................................................................................... 4

Build a simple nail electromagnet and study how electric currents create magnetic felds.

Activity 3: Jump Rope Generator ............................................................................................... 7

Use an extension cord as a jump rope to generate an electrical current.Activity 4: Induction in an Aluminum Can ............................................................................. 10

Students learn about Lenzs Law.


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National Science Education Standards

Standards Key

M - major emphasis

m - minor emphasisi - indirect; i.e., not directly tied to standard, but important background in ormation.

Te letters A-G represent various areas in the National Science Education Standards, as ollows:

A - Science as Inquiry B - Physical Science: Motion and ForcesC - Li e ScienceD - Earth and Space ScienceE - Science and echnology F - Science in Personal and Social PerspectivesG - History and Nature o Science

Activity A B C D E F G Emphasis

1 -PermBar Magnets

M M i m A: [Students] formulate and revise scienti c explanations and models usinglogic and evidence. B: Electricity and magnetism are two aspects of a singleelectromagnetic force. Moving electric charges produce magnetic forces,and moving magnets produce electric forces. G: Scienti c explanations mustmeet certain criteria. First and foremost, they must be consistent with experi-mental and observational evidence about nature, and must make accuratepredictions, when appropriate, about systems being studied.

2 -Electro-

Magnets

M M i m A: [Students] formulate and revise scienti c explanations and models usinglogic and evidence. B: Electricity and magnetism are two aspects of a single

electromagnetic force. Moving electric charges produce magnetic forces,and moving magnets produce electric forces. G: Scienti c explanations mustmeet certain criteria. First and foremost, they must be consistent with experi-mental and observational evidence about nature, and must make accuratepredictions, when appropriate, about systems being studied.

3 -JumpRopeGenera-tor

M M i m A: [Students] formulate and revise scienti c explanations and models usinglogic and evidence B: Electricity and magnetism are two aspects of a singleelectromagnetic force. Moving electric charges produce magnetic forces,and moving magnets produce electric forces. G: Scienti c explanations mustmeet certain criteria. First and foremost, they must be consistent with experi-mental and observational evidence about nature, and must make accuratepredictions, when appropriate, about systems being studied.

4 -Inductionin an AluminumCan

M mM

m A: [Students] formulate and revise scienti c explanations and models us-ing logic and evidence. B: (minor emphasis - Motion & Forces) Electricityand magnetism are two aspects of a single electromagnetic force. Movingelectric charges produce magnetic forces, and moving magnets produceelectric forces. B: (major emphasis - Interactions of Energy & Matter) Insome materials, such as metals, electrons ow easily, whereas in insulatingmaterials such as glass, they can hardly ow at all. G: Scienti c explanationsmust meet certain criteria. First and foremost, they must be consistent withexperimental and observational evidence about nature, and must make ac-curate predictions, when appropriate, about systems being studied.


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Activity NM- ALG.9-12.4 NM-MEA.9-12.1 NM-MEA.9-12.2 Emphasis

1 - Perm.Bar Magnets

N/A

2 - Electromagnets N/A

3 -JumpRopeGenerator

m M M NM-ALG.9-12.4: [Analyze change in various contexts. NM-MEA.9-12.1: Understand measurable attributes of objectsand the units, systems, and processes of measurement .NM-MEA.9-12.2: Apply appropriate techniques, tools, andformulas to determine measurements

4 - Induction in an Aluminum Can

N/A

National Math Standards

NM-ALG.9-12.4: (Algebra). Analyze change in various contexts.NM-MEA.9-12.1: (Measurement). Understand measurable attributes o objects and the units,

systems, and processes o measurement.NM-MEA.9-12.2: (Measurement). Apply appropriate techniques, tools, and ormulas to deter-mine measurements.

Standards Key

M - major emphasism - minor emphasisi - indirect; i.e., not directly tied to standard, but important background in ormation.


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Introduction to the THEMISMagnetism SeriesTis is one o our magnetism activity guidesplus a background guide or teachersthat provide students with the opportunity to build on science concepts related to Earths magnetism andits changes. I your students engage in the activities in these our guides, they will have the skills,language and conceptual understandings o magnetism one-hal o the our undamental orceso nature (the whole orce is known as electromagnetism).

All o these guides have been:

Classroom tested

Checked for science accuracy by NASA and THEMIS scientists

Designed to utilize math and writing

Te goal o these guides is to give students an appreciation o the major role magnetism playson Earth and in space, and ultimately enable them to use NASA data as scientists researchingour magnetic connection to the Sun. We achieve this goal through sequential activities in the ourteachers guides, rom basic explorations with magnets, compasses and galvanometers to scienti cdiscoveries using data rom instruments called magnetometers. Tese magnetometers are locatedin schools across the U.S, as part o the HEMIS education project.

Te our activity guides have been used in di erent types o classes, rom physical science andphysics classes, to geology and astronomy classes. Te excitement o actually participating in the

HEMIS project helps motivate the students to learn challenging physical science concepts.

1. Magnetism and Electromagnetism is a review o basic magnetism, similar to what is encoun-tered in most grade-level physical science texts. Students map eld lines around bar magnets to visualize the magnetic dipole eld, and create their own electromagnet using copper wire, battery and a pencil to learn that electric currents create magnetic elds. wo activities introduce gen-erators and Lenzs law, in one case using Earths magnetic eld and a large conducting wire. Tesematerials can be used by teachers presenting Earth and Physical Science courses in grades 6-9, andwould t well into a lab at the end o a high school physics class. Tese activities are a classroom-ready prerequisite to understanding magnetism on Earth and in space.

2. Exploring Magnetism on Earth is intended to help students explore Earths magnetic eldthrough a variety o math-based activities. Tis guide contains problems ocusing on Earths chang-

ing magnetic eld in time and space. Students use compasses to discover how these changes canimpact navigation on Earths sur ace. Tey use basic math skills to interpret graphical in ormationshowing polar wander and magnetic changes, and answer questions about quantitative aspects o these changes. Tese lessons can be used in geology and astronomy classes.

3. Magnetic Mysteries o the Aurora is a prerequisite to using magnetometer data as students willin the next guide, Earths Magnetic Personality . Magnetic Mysteries o the Aurora introduces stu-dents to Earths magnetic eld and Northern and Southern Lights (aurora) within the context o the


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Sun and space weather. Using worksheets, globes, and a single light source, students review time-keeping on Earthtime zones and Universal ime. Students then go through a series o activitiesto discover the causes o the aurora and their relation to Earths magnetosphere and solar storms.Students classi y images o aurora by shape and color, create a model o Earths magnetosphere, ore-cast magnetic storms using geomagnetic indices, and engage in a presentation about space weather.Tese lessons have been used in physics and astronomy classes as well.4. Earths Magnetic Personality is the culmination o all the previous guides. It was developed withthe goal that students can now work directly with the HEMIS magnetometer data. Students review vectors through calculations, learn to interpret x-y-z magnetometer plots, predict auroral activity using the x-y-z magnetometer data, calculate the total magnetic eld strength and observe it overmonths, and discover that waves in Earths magnetic eld are excited by large magnetic storms by comparing spectrograms with magnetic indices.

5. Te background guide or teachers, the HEMIS GEONS Users Guide, describes the importantrole that terrestrial magnetism plays in shaping a number o important Earth systems. It also ex-plains the basic operating principles behind magnetometersparticularly the system you are nowin the process o using to investigate magnetic storms at your school.


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Activity 1 - Permanent Bar Magnets

Teachers Guide

Although magnets are amiliar household items, students may need to be reminded o the basicproperties o magnets and magnetism. Tis hands-on activity allows students to re-acquaint them-selves with magnets, magnetic elds and the concept o polarity, which orm the basic ingredientso a study o Earths magnetic eld and the technology o magnetometers.

Goals

1. Students will learn the basic properties o mag-nets and magnetic orces.

2. Students will learn about polarity, attraction,repulsion, and magnetic eld strength, whichare the basic terms and concepts we will be us-ing throughout the HEMIS program.

Figure A Te magnetic lines o orcesurrounding a bar magnet revealed byiron flings.

Procedure

Tere are many di erent versions o this activity available on the Internet and you can nd somelocations provided at the end o this teacher guide. Please consult these sites or suggestions ondetailed set-up and speci c tasks the students can per orm. Below is a shortened strategy that willquickly demonstrate the basic phenomena with which we will be working in HEMIS.

1. Distribute the magnets to the students.2. Have them experience, tactilely, the repulsive and attractive natures o magnetic orces. Also, havethem experience, through magnet manipulation and working with paper clips, the idea that mag-netic orces vary in intensity throughout space, becoming weaker as distances increase.

3. Ask one student in the classroom to mark the letter N on one end o a bar magnet. Use thisarbitrarily-de ned North polarity to determine the N and S polarities o all other magnets in theclassroom using the likes repel and opposites attract rule or magnetic polarity.

Materials

A set of bar magnets, two per student. If therearent enough magnets to go around, dividethe class into small groups, with one magnetper group.

10 paper clips per student.


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Magnetic feld surrounding a bar magnet

S N

S N

What structural similarities do you see between the magnetic feld lines sur-rounding the bar magnets, and those seen on the Sun?


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Vocabulary Words

Polarity A property o magnets or electrically-charged objects in which there are two possibleconditions (north and south or magnets, positive and negative or electrical charges) that describean important characteristic o the orces that they experience. Note to teachers: A common mis-

conception is that magnetic poles are positive and negative. Tis is the wrong terminology and o en con uses students into thinking that electrical charges and magnetic charges are thesame things.

Attraction A condition where objects move or are pulled together under the in uence o a orce.

Repulsion A condition where objects move or are pulled apart under the in uence o a orce.

Field An in uence (such as a orce) that some orms o matter produce, which extends through-out the space that surrounds them.

Related Web Activities

1 Exploring Magnetism guide

http://cse.ssl.berkeley.edu/exploringmagnetism

2 Student Observation Network magnetism activity

http://son.nasa.gov/tass/pd /Mapping_Magnetic_In uence.pd

3 IMAGE Playing With Magnetism activity

http://image.gs c.nasa.gov/poetry/activity/l1.htm

4 Exploring Magnetic Fields (IMAGE)

http://image.gs c.nasa.gov/poetry/activity/l2.html


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Activity 2 - Electromagnets

Teachers Guide

Tis activity is commonly per ormed in science classes, starting in 5th grade and extending throughcollege! It relies on the amazing fact, discovered over 100 years ago by Hans Oerstead, that iflet an electric current ow through a copper wire, it will generate a magnetic eld strong enough tode ect a compass needle or pick up bits o iron.

Knowing about the properties o electromagnets is a crucial underpinning or understanding howmagnetic elds are generated in nature, in the sur ace o the Sun, and in the interior o Earth. Inpreparation or this activity, or as a ollow-up, please review with your students the relevant topicsin your Earth Science or Physical Science textbook.

Materials

in insulated wire pencil battery compass paper clips

Figure B Electromagnet made byusing a battery, a pencil and thin,insulated wire.

Tis activity is quite straight orward and considered a classic experiment in electromagnetism,and one which students have usally per ormed at least once by eighth grade. Consult your Physical

Science or Earth Science textbook or detailed plans on how to set up the experiment. Note: We usea pencil rather than a nail because a nail isnt relevant to the electromagnetism phenomenon.You will need to wrap more turns o wire around a pencil, however, in order to achieve a useablemagnetic feld.

For HEMIS, we want students to understand, through this hands-on experiment, that magneticelds can be produced by owing currents or charged particles (electricity!). We also want them to

understand that magnetic elds can be manipulated in strength in one o two easy ways:

Goals

1) Students will see that, when the electri-cal current is turned on, the needle o the compass placed close to the wire willsuddenly point parallel to the pencil.

2) Students will see that the more loops o wire they wind around the pencil, themore paper clips they can pick up.

3) Te more batteries they place in series,the more current will ow through thewire, and again, the stronger will be themagnetic eld.


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1. Tey can control how much current ows in the wire by using several batteries in series to in-crease the current owing in the wire around the pencil.

2. Tey can increase the magnetic eld o the electromagnet by increasing the number o loops o wire wrapped around the pencil.

Tey can measure the strength o the electro-magnet by counting the number o paper clips the nailcan pick up.

Procedure

1. Have the students control how much current ows in the wire by trying di erent numbers o batteries, in series, to change the current owing in the wire around the pencil. Have the stu-dents keep a lab book and record how many paper clips the electromagnet can pick up with eachbattery con guration.

2 Next have students change the magnetic eld o the pencil by changing the number o loops o wire wrapped around the pencil. Again have the students record their observations in their labbook. Te number o paper clips the pencil with coils can pick up indicates the strength o theelectromagnet.

3. In Part A we de ned the polarity o one o the bar magnets as N. Using this same bar magnet,explore the magnetic eld o the electromagnet and determine which end is N and whichend is S. Ten reverse the current direction and repeat this experiment. Ask the students todescribe what happens and why. Tey should note that the polarity depends on the direction o the current ow!

Vocabulary Current A ow o charged particles through a conducting material or through space. Tesecharged particles can be electrons, protons or ions.

Magnetic feld A condition in the space surrounding some objects that causes charged or metallicbodies brought close by to experience the orce o magnetism.

Related Web Activities

1. Exploring Magnetism Activity 2

http://cse.ssl.berkeley.edu/exploringmagnetism/2. Electricity and Magnetism (IMAGE)

http://image.gs c.nasa.gov/poetry/activity/l4.htm


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A Simple Electromagnet


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Activity 3 Jump Rope Generator

Teachers Guide

Your class will demonstrate the generator e ect, which is due to electromagnetic induction whena conductor (a long metal wire) moves through a magnetic eld. In this activity, the magnetic eldyour students work with is Earths magnetic eld and the long wire is an extension cord. Te cordis part o a loop o wire that closes through a galvanometer. Tis loop is important since electricalcurrent must ow in a loop. When the wire is aligned east to west and rotated clockwise or coun-ter-clockwise, it moves across Earths magnetic eld (which points north and downward) allowingthe maximum current to ow. (See the photograph o the teachers on page 8). Tis current can bedetected using the galvanometer. Tis occurs because when a magnetic eld is changed in a loop o wire, a voltage, and hence a current, is induced in the loop. Tis is what happens when the armatureo a generator is rotated, when an iron car drives over a loop o wire imbedded in the roadway toactivate a tra c light, or when a piece o wire is twirled like a jump rope in Earths magnetic eld.When the wire is aligned north to south, it is aligned with Earths magnetic eld and moves acrossEarths magnetic eld only slightly up and down. Moving the wire almost parallel to Earths mag-netic eld means that only a small amount o electrical current will ow through the wire.

Materials

100-foot extension cord withground prong

Current or voltage galvanometer(micro-Ammeter i using a cur-rent galvanometer)

Two lead wires with alligator clipson at least one end

One compass

Goals

1) Students will know that Earth has a magneticeld.

2) Students will observe the de ection o a galvanometer needle when an electrical cordcrosses Earths magnetic eld.

3) Students will record how much the galva-nometer needle is de ected when the electri-cal cord is rotated when aligned east to west versus north to south, and also when thecord is rotated while moving quickly versusmoving slowly.

galvanometer


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Understanding that Earth has a magnetic eld is important to many o NASAs science missions,including HEMIS.

Procedure

1. Attach the alligator clip at the end o one wire to the ground prong o the extension cord. Attachthis wires other end to the galvanometer. ake the second wire, and keeping its alligator clipclosed, push the clip into the ground receptacle on the other end o the extension cord. Attachthe other end o this second wire to the other contact on the galvanometer.

2. Use a compass to align the extension cord in the east-west direction. Leave both ends o theextension cord on the ground. It helps to have two students stand on the cords, near the end, tomake sure the galvanometer stays connected to the cord. Have two additional students pick upthe middle hal o the cord and twirl it like a jump rope. (See the picture below.) It doesnt matterwhether it rotates clockwise or counterclockwise. Have the students observe the galvanometerand record their observations on the worksheet.

3. Have the students twirl the cord aster and observe the galvanometer and record their observa-tions.

4. Repeat step 2, but align the extension cord in the north-west direction again, using a compass.Have the students observe the galvanometer and record their observations.

Teacher Answer Key

1) higher speed means a larger de ection; 2) Te maximum voltage (or current) should occureast-west and ast; 3) Te minimum voltage (or current) should occur north-south and slow;4) the explanation is given above. We recommend you use Question 4 to determine how muchmore discussion or explanation you need to provide the class be ore moving to another topic.


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Student Name _________________________ Date _______

Jump Rope Generator: ObservationsFill out the table with your measurements o greatest de ection on the galvanometer in each o the

our cases. Ten answer the questions below the table.

Cord aligned east-west Cord aligned north-south

Slow

Fast

1. What e ect does the rotational speed o the cord have on the de ection o the galvanometer?

2. Describe the conditions in which you had the maximum voltage (or current) through thegalvanometer.

3. Describe the conditions in which you had the minimum voltage (or current) through the galva-nometer.

4. Explain why the galvanometer needle moves when you play jump-rope with the extension cord.

5. Explain why the the orientation o the jump rope to Earths magnetic eld e ects the galvanom-eter reading.


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Activity 4 Induction in an Aluminum Can

Teachers Guide

In this activity, Lenzs Law is demonstrated. Lenzs Law states that an induced electromotive orcegenerates a current that induces a counter magnetic eld that opposes the magnetic eld generatingthe current. In this activity, an empty aluminum can oats on water in a tray, such as a Petri dish.Students spin a magnet just inside the can without touching the can. Te can begins to spin. Under-standing what happens can be explained in steps:

First, the twirling magnet creates an alternating magnetic eld. Students can use a nearby co-pass to observe that the magnetic eld is really changing.

Second, the changing magnetic eld permeates most things around it, including the aluminumcan itsel . A changing magnetic eld will cause an electric current to ow when there is a closed

loop o an electrically conducting material. Even though the aluminum can is not magnetic, itis metal and will conduct electricity. So the twirling magnet causes an electrical current to owin the aluminum can. Tis is called an induced current.

ird, all electric currents create magnetic elds. So, in essence, the induced electrical currerunning through the can creates its very own magnetic eld, making the aluminum can mag-netic. Now the aluminum cans induced alternating magnetic eld interacts with the twirlingmagnets alternating magnetic eld. Tis interaction spins the can since the magnetic orces areopposed, as Lenzs law states. Because the can sits on top o water, the riction between the canand the sur ace is very small, and only the magnetic orces act on the can while the studentstwirl the magnet .

Acknowledgment or this activity goes to Dindor , W. Lenzs Law in the Kitchen.Te Physicseacher . Vol. 37, May, 1999.

Goals

1) Students will know that electric current can be induced innon-magnetic metals through changing magnetic elds.

2) Students will know that the ormation o an electrical cur-rent causes a magnetic eld.

3) Students will know that magnetic elds interact with oneanother.

4) Students will know Lenzs Law: An induced electromo-tive orce generates a current that induces a counter mag-netic feld that opposes the magnetic feld generating thecurrent.

Materials

Small aluminum can

Container (in which tooat aluminum can)

Spill tray Small cylindrical magnet

(neodymium works best)

read

Tap water


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Procedure

1. Have enough materials on hand or student groups o two. Cat ood cans work well. Just be surethey are made o aluminum. Sof drink cans do not work well. Teir walls are too thin and sharpedges on cut cans poses a sa ety risk. Petri dishes make good oat containers, and Styro oammeat trays will do as spill trays.

2. Have students ll the container in which they will oat the aluminum can as ull as they canwith water. Tey should orm a meniscus at the top o the container so that the aluminum can

oats above the top o the container.

3. Te length o thread should be tied to the center o the magnet so that it hangs straight. Whenyou dangle the magnet into the can, the magnet should also be at least one inch shorter thanthe diameter o the can so that it does not bang into the sides o the can while students attemptto spin it.

4. As you dangle the magnet rom your hand, when you twist the thread between your ngers, themagnet should spin. Students may need to practice this so that they can success ully do it or theactivity.

5. When the spinning magnet is lowered into the can, an electrical current is induced in the alu-minum which is a conductor. Tis electrical current itsel creates a magnetic eld in the metalo the can that opposes the magnetic eld o the spinning magnet. Tese opposing elds causethe can to spin.

6. Tis is a demonstration o an electromagnetic e ect known as Lenzs Law. Explicitly state Lenzslaw ( ound on previous page) to the class.

Teacher Answer Key

1) No. Aluminum is not a magnetic metal; 2) Te compass needle moves and/or the can isspinning; 3) Te can slowly spins; 4) Te answer to how this experiment works can be oundabove. We recommend this question be used to determine i urther discussions or expla-nations are needed with the class.

Meniscus

Petri dish

Aluminumcan

Magnet (suspendedon thread, inside

the can)

thread suspendedfrom your hand


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Student Name _________________________ Date _______

Induction in an Aluminum Can

Please answer the ollowing question related to this activity:

1. Does the aluminum can seem to be magnetic when the magnet is not rotating? Explain youranswer.

2. How can you tell there is a changing magnetic eld near the can?

3. Describe how the aluminum can moves when it is sitting on the water in the Petrie dish with arotating magnet inside.

4. Use your own words and drawings to describe why the magnet causes the can to move.


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National Aeronautics and Space Administration

The Center for Science Education Space Sciences LaboratoryUniversity of California, Berkeley7 Gauss Way, MC 7450Berkeley, CA 94720-7450http://cse.ssl.berkeley.edu

www.nasa.gov

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Mag Electromag