Magnetic Forces ©Lluís Real/Age Fotostock

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LESSON 1 Magnetic Forces ©Lluís Real/age fotostock

Magnets are able to attract or repel certain materials, such as iron, at a distance.

By the end of this lesson . . . © Houghton Mifflin Harcourt • Image Credits: you will be able to describe the variables that affect the strength and direction of the magnetic force.

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© Houghton Mifflin Harcourt • Image Credits: ©Houghton Mifflin Harcourt 2. 1. appear tofloat. another ring.Instead,whentheringsgetnearoneanother, theyare pushedbackupand If youwere todrop oneoftheseringsontoapeg,youwouldnormallyexpectittofallandhit Why do these rings seem to float without touching one another instead of falling? without instead touchingWhy to another float one rings seem dothese explain thebehavior oftherings. EVIDENCE NOTEBOOK What typeofforce mightbeaffecting the motionoftheserings? rings tofloatinsteadoffall? Most objectsare notableto floatinmidair. Whatmustbeoccurringforthese CAN YOU EXPLAIN IT? IT? YOUCAN EXPLAIN As youexplore thelesson, gatherevidencetohelp download additionallabresources. the Hands-OnLabforthislesson andto Go onlinetoviewthedigitalversionof Lesson 1Magnetic Forces ONLINE! Explore 97 LONumber=6P1_0610=CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 98 materials. strong magnetsonlyattract and/or repel certain force variesinpredictable ways.However, evenvery at adistance.Like allforces, thestrength ofmagnetic magnets. Asyoucanseeinthephotos,thisforce acts The magneticforce isthepushorpullexertedby Whydoyouthinkthatthesetwomagnetsare 3. touching. magnets affect eachother, eventhoughtheyare not each other. Look atthephotosandnotice howthe pole. Thesepolesaffect howmagnetsinteract with magnets. Allmagnetshaveanorthpoleandsouth Magnets canattract andrepel, orpushaway, other as cobaltandnickel, are alsoattracted tomagnets. materials thatcontainiron. Othermaterials,such A magnetisanobjectthatattracts, orpullson, Unit 2Electric andMagnetic Forces when theyare nottouching? able toaffect oneanother’s movementseven Describing Magnets and the Magnetic Force 4. EVIDENCE NOTEBOOK to thefloatingrings?Record your evidence. How mighttheabilityofmagnets toattract orrepel othermagnetsrelate EXPLORATION 1 they were notoriginallytouching. magnets affect eachother’s movementeventhough together, theywilljumptoward oneanother. Thetwo When thesemagnetsare brought closeenough magnet hasanorthandsouthpole. red andthesouthpolehasbeenpaintedgray. Every are different colors.Thenorthpolehasbeenpainted The north and south poles of the magnets in this image Magnet Interactions Magnet Explore ONLINE!

Hands-On Lab Explore the Behavior of Magnets

You will ask questions to investigate the behavior of magnets and then you will MATERIALS explore how magnets affect a variety of materials and identify the factors that affect the strength of the magnetic force. • bar magnet, identical (2) • large magnet (1) Procedure • strip, copper STEP 1 Below are a few questions to consider as you explore the factors that • strip, iron affect the strength of the magnetic force. Write at least two more • strip, plastic questions you could investigate using the materials. • How do the magnets affect materials that are not magnets? • How does the force between the two bar magnets compare to the force between the other magnet and a bar magnet? • How do the poles of the magnets affect the force they exert on each other?

STEP 2 Choose two questions to investigate. Identify the variables you will be testing for each investigation. Revise your questions if needed so your investigation will help you determine whether there is a relationship between the variables, and if so, what that relationship is. On a separate sheet of paper, write your procedure for each question and record your observations.

Analysis STEP 3 Discuss With a partner, compare your observations. Using your combined observations, decide on the factors that seemed to affect the strength of the magnetic force. Record your answers below.

STEP 4 The magnetic force is attractive / repulsive when two like poles point toward each other. The magnetic force is attractive / repulsive when two opposite poles point toward each other. When the like poles of two magnets point toward one another, the strength of the magnetic force is the same as when the opposite poles point toward one another. © Houghton Mifflin Harcourt

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Hands-On Lab Analyze the Magnetic Force

Part 1: Distance and the Magnetic Force MATERIALS You will investigate the relationship between distance and the strength of the • bar magnet magnetic force using a magnet and a compass. The needle of a compass is • compass magnetic and points north due to Earth’s magnetic field. If the attractive force • tape between the compass needle and a magnet is strong enough, the compass • tape measure or ruler needle will move toward the magnet. The distance between two magnets affects the strength of the magnetic force. When two magnets are moved closer together, the magnetic force between them increases. When two magnets are moved farther apart, the magnetic force between them decreases.

Procedure and Analysis ©Houghton Mifflin Harcourt STEP 1 Tape your compass to the table so that the needle points directly toward one of the sides of the compass. Record the direction in degrees that the compass needle is pointing.

STEP 2 Place the bar magnet so that the south pole of the magnet is pointed toward the compass. It should be far enough away that it does not affect the needle. The needle and the magnet should be perpendicular to one another.

STEP 3 Move the magnet straight toward the compass until the needle moves 15° © Houghton Mifflin Harcourt • Image Credits: from its starting position. Record the distance between the edge of the bar magnet closest to the compass and the edge of the compass.

STEP 4 Move the magnet four more times, recording the distance and the position of the needle in degrees. Choose increments so that your last data point is collected with the magnet touching the compass.

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STEP 5 Record the number of degrees the needle moved from its starting position for each Distance Needle Position distance, or measured position. (cm) (degrees)

STEP 6 Do the Math Make a graph of your data with degrees on the y-axis and distance on the x-axis. Graphs can help you clearly see the relationship between variables in an experiment.

STEP 7 Look at the trend shown in your graph. Consider how the strength of the magnetic force relates to the needle position. What effect does distance seem to have on the strength of the magnetic force? © Houghton Mifflin Harcourt

Lesson 1 Magnetic Forces 101 LONumber=6P1_0610=CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 102 Procedure andAnalysis material andsizeofamagnetaffect thestrength ofthemagneticforce. magnet. Somemagnetsproduce astronger magnetic force thanothers.The comparing themasses thattheycanhold. You willtestthestrength ofthemagneticforces produced bytwomagnets STEP 6 STEP 5 STEP 4 STEP 3 STEP 2 STEP 1 Unit 2Electric andMagnetic Forces The strength ofthemagneticforce exertedbyamagnet dependsonthe

Repeat Steps2–4withthelarge magnet. measure themaximummass thateachmagnetcanhold. not havea150gmass, howcouldyoumeasure this?Developaprocess to supplies. Ifyouhadamagnetthatcouldholdmaximumof150g,butdid measurements more accurate usingyour Consider howyoucouldmake your the paperclip. mass, untilthemagnetcannolongerhold and masses, gradually increasing the Repeat Step2withtheotherpaperclips Remove thepaperclipandmass. the lightestmass from thebarmagnet. Hang theendofpaperclipwith Hook eachmass toapaperclip. magnetic force thatyoulearned before thisinvestigation. and explainyourreasoning. You canalsodraw oninformationaboutthe magnetic force. Useevidence from yourobservationstosupportclaim, Magnetic Force Magnetic Part 2: Magnet Strength and the how youbelievethetypeofmagnetaffects thestrength ofthe Record yourobservations.Write aclaimthatstates Language SmArts as set,hooked • mass clips, • paper • magnet, large • magnet, bar MATERIALS (10 g–1kg) metal (10)

© Houghton Mifflin Harcourt • Image Credits: ©OTHK/Asia Images/Getty Images STEP 7 Themagneticforce pushingthetrain awayfrom thetracks isstrong enough to 6. float, orlevitate,abovethetracks. objects. Maglevtrains cantravel atveryhighspeedsbecausetheyusemagneticforce to clasp onabagorrefrigerator magnet.Amagneticforce canalsobeusedtopushapart magnets. Amagneticforce often isusedtoholdtogetherobjects,suchasmagnetic whether thelike oroppositepolesare facingeachother, magnetspushorpullonother Magnets exertamagneticforce thatcanpulloncertainmaterials. Dependingon Analyze How Magnets Are Used magnets onthetrain were reversed, whatwould happentothetrain? overcome theforce ofgravity, allowingthetrain tolevitate. Ifthepolesof

5. EVIDENCE NOTEBOOK D. Thestrength ofthebarmagnetisgreater thanthestrength ofthelarger C. Thestrength ofthebarmagnet is less thanthestrength ofthelarger B. Thestrength ofthebarmagnetisgreater thanthestrength ofthelarger A. magnets basedonthemagneticforce thattheyexert? Based onyourobservations,whatcanyouinferaboutthestrength ofthe Thestrength ofthebarmagnetisless thanthestrength ofthelarger forces actingontherings?Record yourevidence. behavior oftherings?Ifso,howcanthesevariablesberelated tothe Do distanceandthestrength ofdifferent magnetsseemtoaffect the magnet becausethebarproduces astronger magneticforce. magnet becausethebarproduces astronger magneticforce. magnet becausethebarproduces aweaker magneticforce. magnet becausethebarproduces aweaker magneticforce. Lesson 1Magnetic Forces friction. levitate, eliminating magnetic force to train usesastrong tracks. Instead,the that roll onthe not havewheels A maglevtrain does 103 LONumber=6P1_0610=CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 104 Inasmalliron particlemadeof200atoms,the 8. magnetic forces, mostmaterialsare notmagnetic. magnetic force. Duetotheserandomly oriented in alldirections, thematerial willnotproduce anet north andsoutheachpole.Ifthepolesare oriented atoms canbethoughtofastinymagnets,witha a stronger magneticforce thanotheratoms.These magnetic forces. Someatoms, suchasiron, produce Many atomsandmoleculesgenerate verysmall of theoverall magneticproperties ofitsatoms. The magneticproperties of amaterialare aresult Atoms and Magnets Whenamagnetiscutinhalf, bothhalvesbecomemagnetswithnorthandsouth 7. that generate amagneticforce andare attracted tomagnets. same way. There issomethingfundamentallydifferent abouttheproperties ofmaterials displays magnetism,othermetalssuchascopperaren’t attracted tomagnetsinthe Magnets displayproperties thatare uniquetoaselect group ofmaterials.Whileiron Unit 2Electric andMagnetic Forces D. C. The B. The A. The force exertedbytheiron particle? left. Whichstatementdescribesthenetmagnetic the northpolesofanother100atomsare pointed north polesof100atomsare pointedrightand are cutinhalf? poles. Whydoyouthinkmagnetsalwayshavenorthandsouthpoles,evenafter they The as theforce of theatoms. as theforce oftheatoms. net magneticforce is100timesasstrong net magneticforce isless thanzero. net magneticforce isaboutzero. net magneticforce is200timesasstrong Exploring Why Materials Are Magnetic EXPLORATION 2 average tonearlyzero, producing nooverall magneticforce. different directions. Asaresult, thetinymagneticforces north andsouthpoles.Noticethat polespointinmany The atomsinthismaterialare represented asmagnetswith

© Houghton Mifflin Harcourt Iron nailsare attracted tomagnets,buttheyare notattracted toeachother. Explain 9. ferromagnetic materials.Iron, nickel, andcobaltare allexamplesofferromagnetic materials. the polesofatomsinanotherdomain.Materialsthatformmagneticdomainsare called direction. However, thepolesofatomsinonedomainmaypointadifferent direction than atoms pointinthesamedirection, sotheirmagneticfieldsare alsoalignedinthesame direction inareas calledmagneticdomains.Withineachdomain,thelike polesofthe In somematerials,suchasiron, thenorthpolesofgroups ofatomscanlineupinthesame Domains Magnetic Inthespaceon 10. Draw Magnetic Alignment Domain why iron nailsmaybehavethisway. representing thenorthpole. domains, withthearrowhead alignment ofthemagnetic Use arrows toshowthe the northpoleofamagnet. appear whenplacednear domains ofaniron nailmight sketch howthemagnetic are neareachother. Next, nails mightappearwhenthey magnetic domainsoftwoiron the right,sketch howthe 11. EVIDENCE NOTEBOOK about themagnetic domainsoftheseobjects? Record yourevidence. What kindofforce didthelevitatingringsdisplay?What doesthissay magnetic domainsalwaysremain aligned. magnets generate anetmagneticforce becausetheir causes iron tobeattracted tomagnets.Permanent temporarily becomesamagnet.Thisrealignment magnetic domainsbecomealignedandthematerial a magneticforce, thedomainsrealign themselves.The When amaterialwithmagneticdomainsisexposedto a magneticforce onotherobjects. either zero orverysmall,iron doesnotnormallyexert sum ofthemagneticforces ofthedifferent domainsis normally pointinrandom directions. Becausethe can havemagneticdomains.However, thedomains Materials thatare attracted tomagnets,suchasiron, Lesson 1Magnetic Forces 105 DO NOT EDIT--Changes must be made through “File info” LONumber=6P1_0610=CorrectionKey=NL-B

Engineer It Though we know magnetic domains exist, they are not visible to the human eye. In addition to being very small, the domains are not visible under normal circumstances. However, a special method can be used to visualize them. The Kerr microscope makes use of the fact that the magnetic force affects light in subtle ways. The Kerr microscope first shines light through a filter. The light then bounces off of the magnetic material and is changed slightly by the magnetic force. The light then passes through another filter. Due to this filter system, the change in the light due to the material’s magnetism can be seen with the microscope. In order to understand how a technology such as this could be developed, identify which statement matches the following steps of the engineering design process. Not every item in the word bank will be used.

12. Scientists are unable to visualize the magnetism of materials. WORD BANK • defining engineering problems 13. Scientists discover that the magnetic strength of a material can • developing solutions affect how light interacts with the material. • testing solutions • optimizing solutions

14. A microscope designed to measure how light changes after it reflects off of a magnetic object is run through several trials to test if it works correctly.

©Kirill

Analyze Temporary Magnets A magnetic domain is a group of atoms with their poles aligned in the same direction. In permanent magnets, the magnetic domains are aligned with each other to produce a net magnetic force. Some materials can become temporary magnets. This iron screwdriver temporarily became magnetic after it was exposed to a strong magnet.

15. How did the screwdriver become temporarily magnetic? A. Magnetic domains formed in the metal of the screwdriver when it was exposed

to the magnet. (t) ©Javier Larrea/age fotostock; (b) © Houghton Mifflin Harcourt • Image Credits: Zdorov/iStock/Getty Images Plus/Getty Images B. The magnetic domains in the screwdriver were temporarily aligned by the presence of the magnet. C. The force exerted by the screws made the magnetic domains in the metal of the screwdriver line up. D. The magnet erased the magnetic domains in the screwdriver.

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TAKE IT FURTHER

Continue Your Exploration

Name: Date:

Check out the path below or go online to choose one of the other paths shown.

Investigate • Hands-On Labs Go online to choose one Permanent • Magnets in Everyday Life of these other Magnets • Propose Your Own Path paths.

Lodestone, like the one in the photo were used for centuries to make compasses. Lodestones are naturally occurring permanent magnets made of iron oxide. This material contains a large amount of iron, as well as the element oxygen. Iron oxide is also called magnetite because of its magnetic properties. ©DEA/PHOTO 1/Getty Images

1. A small group of atoms of magnetite will exert less magnetic force than the same number of iron atoms. Despite this, lodestones are permanent magnets, and pure iron is not. How can magnetic domains explain why the magnetic properties of

© Houghton Mifflin Harcourt • Image Credits: © Houghton Mifflin Harcourt • Image Credits: lodestones differ from the properties of pure iron? A. The magnetic domains in lodestones are bigger than those in iron. B. The poles within each magnetic domain in lodestones line up, but they cancel each other out within each domain in iron. C. The magnetic domains in lodestones cannot change their alignment, but those in iron are free to change their orientation.

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TAKE IT FURTHER

Continue Your Exploration

The magnet on the left The magnet on the right is is a ferrite magnet. a neodymium magnet. The neodymium magnet is much stronger than the ferrite magnet.

Human-Made Magnets Scientists and engineers have learned how to make magnetic materials. Ferrite is a magnetic material that is composed of iron and oxygen as well as other elements. Rare earth elements, such as neodymium, are also used to make permanent magnets. The magnets made using these rare earth elements are extremely strong.

2. Why might rare earth magnets be so strong? Cite specific details from the lesson about the strength of magnets and magnetic domains to support your answer. ©Houghton Mifflin Harcourt

3. How will the effect of a rare earth magnet on a piece of iron compare to the effect of a lodestone on the same piece of iron? A. Both magnets will be able to move the iron from the same distance. B. The lodestone will be able to move the iron from a greater distance. C. The rare earth magnet will be able to move the iron from a greater distance.

D. The lodestone will repel iron, and the rare earth magnet will attract it. © Houghton Mifflin Harcourt • Image Credits:

4. Collaborate Compare your answers in this activity with those of a partner. Discuss how you arrived at each answer. Consider how stronger human-made magnets could be created. What would have to be true about a new material in order for it to generate a stronger magnetic force than current magnets do?

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LESSON 1 SELF CHECK

Can You Explain It?

Name: Date:

Why do these rings seem to float without touching one another instead of falling?

Explore ONLINE!

EVIDENCE NOTEBOOK Refer to the notes in your Evidence Notebook to help you construct an explanation for why the rings in the photo levitate instead of simply falling.

) 1. State your claim. Make sure your claim fully explains how the rings float.

2. Summarize the evidence you have gathered to support your claim and explain your reasoning. ©Houghton Mifflin Harcourt ( (t) © Houghton Mifflin Harcourt • Image Credits: © Houghton Mifflin Harcourt • Image Credits:

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LESSON 1 SELF CHECK

Checkpoints

Answer the following questions to check your understanding of the lesson. Use the photo to answer Questions 3 and 4. 3. If the magnet on the right is flipped so that the south pole is on the left, the magnetic force will be attractive / repulsive. As the two magnets are moved closer together, the magnetic force between them will become stronger / weaker.

4. If the two magnets were cut in half along the line between the red and blue paint, which statement would describe the four bars that are produced? A. Each piece would have one magnetic pole and a nonmagnetic end. B. Each piece would have a north pole and a south pole. C. Two pieces would only have south poles and the other two pieces would only have north poles.

Use the photo to answer Questions 5 and 6. 5. Which statements describe the iron-containing rock and the nails? Choose all statements that apply. A. The rock is a magnet. B. The nails are attracted to magnets. ©Mary

C. Most of the magnetic domains in the ; (b) rock are randomly oriented. D. Most of the magnetic domains in the rock are aligned with each other. WORD BANK

• increase (t) it would affect the magnetic force present • decrease in the photograph. • not affect A. Removing half of the rock would the magnetic force. B. Moving the rock and nails higher would the magnetic force. C. Increasing the distance between the rock and the nails would the magnetic force. © Houghton Mifflin Harcourt • Image Credits: Evans Picture Library/The Natural History Museum/age fotostock D. Using copper nails instead of iron nails would the magnetic force. E. Replacing the rock with a similarly sized stronger magnet would the magnetic force.

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© Houghton Mifflin Harcourt • Image Credits: (t) (©Houghton Mifflin Harcourt) domains thatformwithinthematerial. The magneticproperties of materialsare aresult oftheiratomsandthemagnetic Theelementcobaltdisplaysmanysimilaritiestotheiron andisalso B. Complete this to review section the main concepts of the lesson. orientation ofthoseobjects. on thestrength ofthemagnet,distanceinbetweenmagneticobjects,and A magnetisamaterialthatattracts iron. Theforce thatamagnetgenerates depends magnetic domains?Explainyouranswer. attracted tomagnets. Basedonthisinformation,isitlikely thatcobaltforms Interactive Review LESSON 1 SELF CHECK 1 LESSON A. the paperclip? be donetoincrease theeffect ofthemagneton move asthemagnetpasses overit.Whatcould desk. Apaperclipresting onthedeskbeginsto A magnetispassed tencentimetersabovea Lesson 1Magnetic Forces 111