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13Fun with MagnetsPaheli and Boojho went to a placewhere a lot of waste material waspiled into huge heaps. Somethingexciting was happening! A crane wasmoving towards the heap of junk. Thelong hand of the crane lowered a blockover a heap. It then began to move.Guess, what? Many pieces of iron junkwere sticking to the block, as it movedaway (Fig. 13.1)!sticking to the holder. In some pencilboxes, the lid fits tightly when we closeit even without a locking arrangement.Such stickers, pin holders and pencilboxes have magnets fitted inside(Fig. 13.2). If you have any one of theseitems, try to locate the magnets hiddenin these.Fig. 13.2 Some common items that havemagnets inside themFig. 13.1 Picking up pieces of iron from wasteThey had just read a very interestingbook on magnets and knew immediatelythat there must be a magnet attachedto the end of the crane that was pickingup iron from the junk yard.You might have seen magnets andhave even enjoyed playing with them.Have you seen stickers that remainattached to iron surfaces like almirahsor the doors of refrigerators? In somepin holders, the pins seem to beHow Magnets Were DiscoveredIt is said that, there was a shepherdnamed Magnes, who lived in ancientGreece. He used to take his herd ofsheep and goats to the nearbymountains for grazing. He would takea stick with him to control his herd. Thestick had a small piece of iron attachedat one end. One day he was surprisedto find that he had to pull hard tofree his stick from a rock on the2021–22

Fig. 13.4 Magnets of different shapesmagnets are prepared in differentshapes. For example, bar magnet, horseshoe magnet, cylindrical or a ball-endedmagnet. Fig.13.4 shows a few suchmagnets.Fig.13.3 A natural magnet on a hillside!mountainside (Fig. 13.3). It seemed asif the stick was being attracted by therock. The rock was a natural magnetand it attracted the iron tip of theshepherd's stick. It is said that this ishow natural magnets were discovered.Such rocks were given the namemagnetite, perhaps after the name of thatshepherd. Magnetite contains iron.Some people believe that magnetite wasfirst discovered at a place calledMagnesia. The substances having theproperty of attracting iron are now knownas magnets. This is how the story goes.In any case, people now havediscovered that certain rocks have theproperty of attracting pieces of iron. Theyalso found that small pieces of theserocks have some special properties.They named these naturally occurringmaterials magnets. Later on the processof making magnets from pieces of ironwas discovered. These are known asartificial magnets. Nowadays artificialActivity 1Take a plastic or a paper cup. Fix it on astand with the help of a clamp as shownin Fig. 13.5. Place a magnet inside thecup and cover it with a paper so thatthe magnet is not visible. Attach athread to a clip made of iron. Fix theother end of the thread at the base ofthe stand. (Mind you, the trick involvedhere, is to keep the length of the threadsufficiently short.) Bring the clip nearthe base of the cup. The clip is raised inair without support, like a kite.126Fig. 13.5 Effect of magnet - a paper cliphanging in air!SCIENCE2021–22

13.1 MAGNETICMATERIALSANDNON-MAGNETICActivity 2Let us walk in the footsteps of Magnes.Only, this time, we will change thepositions of the magnet and the iron.There will be a magnet at the end of ourshepherd's stick. We can attach a smallmagnet to a hockey stick, walking stickor a cricket wicket with a tape or someglue. Let us now go out on a "Magneswalk" through the school playground.What does our "Magnes stick" pick upfrom the school ground? What aboutobjects in the classroom?Collect various objects of day-to-dayuse from your surroundings. Test thesewith the "Magnes stick". You can alsotake a magnet, touch these objects withit and observe which objects stick to themagnet. Prepare a table in yournotebook as shown in Table 13.1. andrecord your observations.Look at the last column of Table 13.1and note the objects that are attractedby a magnet. Now, make a list ofmaterials from which these objects aremade. Is there any material common inall the objects that were attracted bythe magnet?We understand that magnet attractscertain materials whereas some do notget attracted towards magnet. Thematerials which get attracted towardsa magnet are magnetic – for example,iron, nickel or cobalt. The materialswhich are not attracted towards amagnet are non-magnetic. Whatmaterials did you find to be nonmagnetic from Table 13.1? Is soil amagnetic or a non-magnetic material?Boojho has this question for you.A tailor was stitching buttons onhis shirt. The needle has slippedfrom his hand on to the floor.Can you help the tailor tofind the needle?Table 13.1 Finding the objects attracted by magnetMaterial which the object is made of(Cloth/plastic/ aluminium/ wood/glass/ iron/ any otherAttracted by Magnesstick/ magnet(Yes/No)Iron ballIronYesScalePlasticNoShoeLeather?Name ofthe object127FUN WITH MAGNETS2021–22

Activity 3Rub a magnet in the sand or soil. Pullout the magnet. Are there some particlesof sand or soil sticking to the magnet?Now, gently shake the magnet to removethe particles of sand or soil. Are someparticles still sticking to it? These mightbe small pieces of iron (iron filings)picked up from the soil.Through such an activity, we canfind out whether the soil or sand from agiven place contains particles that haveiron. Try this activity near your home,school or the places you visit on yourholidays. Does the magnet with ironfilings sticking to it, look like any oneof those shown in Fig. 13.6?Make a table of what you find.(a)If you fill this table and send it toPaheli and Boojho, they can comparethe amount of iron filings found in soilfrom different parts of the country. Theycan share this information with you.13.2 POLESOFMAGNETWe observed that iron filings (if they arepresent) stick to a magnet rubbed in thesoil. Did you observe anything specialabout the way they stick to the magnet?Activity 4Spread some iron filings on a sheet ofpaper. Now, place a bar magnet on thissheet. What do you observe? Do the ironfilings stick all over the magnet? Do youobserve that more iron filings get attractedto some parts of the magnet than others(Fig. 13.7)? Remove the iron filingssticking to the magnet and repeat the(b)(c)Fig. 13.6 Magnet with (a) many iron filings(b) few iron filings and(c) no iron filings sticking to it.Fig. 13.7 Iron filings sticking to a bar magnetTable 13.2 Magnet rubbed in sand.How many iron filings?id you find ironName of location fDilings sticking to(Colony andthe magnet?town/ city/(Many/ very few/village)none)activity. Do you observe any change inthe pattern with which the iron filingsget attracted by different parts of themagnet? You can do this activity usingpins or iron nails in place of iron filingsand also with magnets of different shapes.Draw a diagram to show the way ironfilings stick to the magnet. Is your drawingsimilar to that shown in Fig. 13.6 (a)?We find that the iron filings areattracted more towards the region close128SCIENCE2021–22

Paheli has this puzzle for you.You are given two identical barswhich look as if they might bemade of iron. One of them is amagnet, while the other is asimple iron bar. How willyou find out, which oneis a magnet?to two ends of a bar magnet. Poles of amagnet are said to be near these ends.Try and bring a few magnets of differentshapes to the classroom. Check for thelocation of the poles on these magnetsusing iron filings. Can you now mark thelocation of poles in the kind of magnetsshown in Fig. 13.4?13.3 FINDING DIRECTIONSMagnets were known to people fromancient times. Many properties ofmagnets were also known to them. Youmight have read many interestingstories about the uses of magnets. Onesuch story is about an emperor in Chinanamed Hoang Ti. It is said that he hada chariot with a statue of a lady thatcould rotate in any direction. It had anextended arm as if it was showing theway (Fig. 13.8). The statue had aninteresting property. It would rest insuch a position that its extended armalways pointed towards South. Bylooking at the extended arm of thestatue, the Emperor was able to locatedirections when he went to new placeson his chariot.Fig. 13.8 The chariot with direction finding statueLet us make such a direction finderfor ourselves.Activity 5Take a bar magnet. Put a mark on oneof its ends for identification. Now, tie athread at the middle of the magnet sothat you may suspend it from a woodenstand (Fig. 13.9). Make sure that themagnet can rotate freely. Let it come torest. Mark two points on the ground toshow the position of the ends of themagnet when it comes to rest. Draw aFig. 13.9 A freely suspended bar magnetalways comes to rest in the same direction129FUN WITH MAGNETS2021–22

line joining the two points. This lineshows the direction in which the magnetwas pointing in its position of rest. Now,rotate the magnet by gently pushing oneend in any direction and let it come torest. Again, mark the position of the twoends in its position of rest. Does themagnet now point in a differentdirection? Rotate the magnet in otherdirections and note the final directionin which it comes to rest.Do you find that the magnet alwayscomes to rest in the same direction?Now can you guess the mystery behindthe statue in the Emperor's chariot?Repeat this activity with an iron barand a plastic or a wooden scale insteadof a magnet. Do not use light objects forthis activity and avoid doing it wherethere are currents of air. Do the othermaterials also always come to rest in thesame direction?We find that a freely suspended barmagnet always comes to rest in aparticular direction, which is the NorthSouth direction. Use the direction of therising sun in the morning to find outthe rough direction towards east, whereyou are doing this experiment. If youstand facing east, to your left will beNorth. Using the Sun for findingdirections may not be very exact, but, itwill help to make out the directionNorth from the South, on your line.Using this you can figure out which endof the magnet is pointing to the Northand which points to the South.The end of the magnet that pointstowards North is called its North seekingIn which direction is the maingate of your school situated fromyour classroom?end or the North pole of the magnet. Theother end that points towards the Southis called South seeking end or the Southpole of the magnet. All magnets have twopoles whatever their shape may be.Usually, north (N) and south (S) polesare marked on the magnets.This property of the magnet is veryuseful for us. For centuries, travellershave been making use of this propertyof magnets to find directions. It is saidthat in olden days, travellers used to finddirections by suspending naturalmagnets with a thread, which theyalways carried with them.Later on, a device was developedbased on this property of magnets. It isknown as the compass. A compass isusually a small box with a glass coveron it. A magnetised needle is pivotedinside the box, which can rotate freely(Fig. 13.10). The compass also has a dial130Fig. 13.10 A compassSCIENCE2021–22