Presentation on theme: "Bellwork: Monday 5/21/2012 What causes a compass to behave as it does?"— Presentation transcript:
1 Bellwork: Monday 5/21/2012 What causes a compass to behave as it does? Earth’s gravityEarth’s shapeEarth’s geographic north poleEarth’s magnetic fieldMagnetic poles that are alikeattract each otherrepel each otherdo not interacthave the same shapeAs in the case of unlike magnetic poles, unlike electric chargesexist in pairsEarth’s magnetic field…causes a compass to behave as it doesMagnetic poles that are alike…repel each otherUnlike electric charges...attract each other
2 Packet 16, Pg 1- History of Magnetism 2000+ years agoGreeks near the city of Magnesia found strange and rare stones with the power to attract iron—called them magnetite (Fe3O4)Lodestone- naturally magnetized piece of magnetite1000 years agoChinese stroked a steel needle with “lodestone” (‘lode’ means to lead or to attract) and it became "magnetic" as well.When freely suspended, it pointed north-south. The magnetic compass soon spread to Europe.
3 Christopher Columbus- 1492 Used a compass when he crossed the Atlantic oceanHis observations:the compass needle strayed slightly from exact northas indicated by the starsthe variation changed during the voyage
4 But, they did not understand how it worked! What’s happening?Basically, people knew the magnetism existed, and learned useful applications for it.But, they did not understand how it worked!500 years agoWilliam Gilbert, physician to Queen Elizabeth I of England, proposed an explanation:“The Earth itself is a giant magnet, with its magnetic poles some distance away from its geographic poles”Geographic poles- the points defining the axis around which the Earth turns
5 Safety with Magnets Magnets should not be held near these things: Credit cardsMagnetic I.D. cardsTV or VCRComputer monitorFloppy computer discsCassette Tapes/ Video TapesTape RecordersRadioAny SpeakersA magnet will harm most electrical devices!!!
6 Using Magnetism for Evil?! Magneto is a powerful mutant with the ability to generate and control electromagnetic forces.He can shape and manipulate magnetic fields that exist naturally or artificially.Magneto has been the X-Men's most prominent enemy ever since his first appearance.
7 Magnetic Force4.5- TSW DESCRIBE THE FOLLOWING FORCE: MAGNETISM.6.14- TSW DEMONSTRATE THE PROPERTIES THAT CAN BE USED TO IDENTIFY MATTER: MAGNETISM.Magnetism- physical property of a substance; the force of attraction or repulsion of magnetic materialsForce is stronger than gravitational force (allows us to pick up objects using a magnet )Magnetic fields:Can be mappedMore field lines indicates the strength of the magnet in that areaStrongest near the poles Stronger closer to the magnet than further away.7.20- TSW DEMONSTRATE THAT THE STRENGTH OF THE MAGNETIC FORCE DEPENDS ON THE DISTANCE BETWEEN THE MAGNET AND OBJECTS.
8 Properties of Magnets S N S N S N S N All magnets have two opposite poles.No matter how small or broken, each piece will have its own positive and negative pole. There are no unpaired poles. Poles have been labeled as north and south.A magnet is capable of producing an electric current.When poles get near each other, they exert magnetic forces on each otherMagnetic poles that are alike repel each other.Magnetic poles that are different attract each other.SNSNSN
9 MagnetismParamagnetism - When a paramagnetic material is placed near a magnet, it will be attracted to the region of greater magnetic fieldExhibited by: materials containing transition elements, rare earth elements and actinide elements Diamagnetism - When a diamagnetic material is placed near a magnet, it will be repelled from the region of greater magnetic fieldExhibited by: all common materials, but is very weakEx. People, frogsEx. Metals such as bismuth, copper, gold, silver and lead, as well as many nonmetals such as water
10 "Magnetic Man" Malaysia, Liew Thow Lin, 70 years old Has the ability to make metal objects stick to his skin.After reading an article about a family in Taiwan who possessed such power, he says he took several iron objects and put them on his abdomen, and to his surprise, all the objects including an iron, stuck on his skin and didn't fall down.Pulled a car 20m along a level surface by means of an iron chain hooked to an iron plate on his midriffSince this "gift'' is also present in three of his sons and two grandchildren, he figures it's hereditary.
11 The boy with the magnetic personality May 11, 2011Six-year-old Croatian, Ivan Stoiljkovic, can stick metal objects to his body such as: spoons, mobile phones and even frying pansReality: Doctors say he's ability is related to suction properties in his skin and not to magnetic force but anyway what he can do is very impressive.
12 3 Types of MagnetsNatural (Permanent) Magnet- A magnet that retains its magnetization after removal from a magnetic field.Can occur naturally.Lodestone is a natural permanent magnet.Can produce forces at all timesEarth produces a magnetic field due to molten iron in core and spinning of the earthPermanent magnets can be damaged from extreme heat and dropping
13 Permanent MagnetsEach atom in a ferromagnetic material like iron is like a little magnet.These magnets are all aligned in tiny regions called “domains”.At high temps these “domains” can align in the presence of an external field (like Earth’s) leaving a permanent magnet.Lets melt the iron, and bring in a magnetic field.TempNow, when we let the solid cool down, and take away the external magnetic field, we have formed a permanent magnet in the same direction as external field.Melting pointDomainsBar Magnet
14 3 types of magnets2. Temporary Magnet- only have magnetic properties for a short period of time, after exposure to a permanent magnetIron—composed of molecules (domains)All different directions = no magnetic force or pullAll lined up in one direction = force to pull things towards them
15 Groups of atoms join so that their magnetic fields are all going in the same direction These areas of atoms are called “domains”An unmagnetized substance looks like:While a magnetized substance looks like:
16 1. Impact (hit it) 2. Heat it 3. Electricity How to demagnetize a magnet:1. Impact (hit it)2. Heat it3. ElectricityThis causes the domains to become random again!
17 3 types of Magnets3. Electromagnet- temporary magnet, made by coiling wire around a piece of soft iron.7.18- TSW PROVIDE EVIDENCE THAT ELECTRIC CURRENTS CAN PRODUCE MAGNETIC FORCES.7.19- TSW PROVIDE EVIDENCE THAT MAGNETS CAN CAUSE ELECTRIC CURRENTS.When an electric current is passed through the wire, a magnetic field is produced.The field magnetizes the iron core by aligning domains within the iron.
18 Bellwork: Tuesday 5/22/2012 Attract Attract Repel S N S N S N What happens if a magnet breaks in half?One half has a north pole only, and one half has a south pole onlyNeither half will have a poleEach half will be a new magnet, with both a north and south poleNeither half will attract or repel.Draw arrows to show if the cars attract or repel each other. On the space to the right, write the word that describes the action of the cars (attract or repel).The region around a magnet where the magnetic force is exerted is known as itsmagnetic polemagnetic fieldmagnetic domainMagnetism can be considered anuclear propertyphysical propertychemical propertyA temporary magnetkeeps its magnetism for a long timecannot be destroyedeasily loses its magnetismAttract Attract Repel SNSNSN
19 What on Earth is a Cow Magnet? Magnets come in many shapes and sizes, but the cow magnet was invented to solve a very serious problem of dairy farmers.When the cow grazes, it often consumes and swallows small pieces of iron: baling and barbed wire, staples, nails, and other metallic objects.These objects are indigestible and lodge in the reticulum and cause inflammation.This results in lower milk production (for dairy cattle) or lower weight gain (for feeder stock).This condition is called hardware disease.Solution: A rancher/ farmer feeds a magnet to each calf at branding time; the magnet settles in the rumen or reticulum and remains there for the life of the animal.The cow magnet attracts such objects and prevents them from becoming lodged in the animal's tissue. While the resultant mass of iron remains in the cow's rumen as a sort of bezoar, it does not cause the severe problems of hardware disease.One small cow magnet can help a cow for her whole life!
20 Magnetic Fields- pg. 3 Procedure: Place a magnet into a tray, put a piece of paper over the magnet.Lightly sprinkle iron filings on and around the magnet, gently tap the paper.Observe the formation around the magnets, and sketch what you see.Types of Demonstration:One magnetTwo magnets- AttractingTwo magnets- Repelling
21 Mapping Magnetic Fields One MagnetTwo Magnets- AttractingTwo Magnets- RepellingNSNSNSNSSN
22 MAGNETIC FIELDS- One Magnet This picture demonstrates what occurs when one magnet is placed on paper, and iron filings are sprinkled around it.
23 MAGNETIC FIELDS- Two Magnets Attracting This picture has two magnets placed on a piece of paper with their opposite poles facing each other, and iron filings are sprinkled around them.
24 MAGNETIC FIELDS- Two Magnets Repelling Pictured here are two magnets placed on a piece of paper with their like poles facing each other, and iron filings are sprinkled around them.
26 The Earth’s magnetic field extends far into space The Earth’s magnetic field extends far into space. It is called the “magnetosphere.”When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called…
27 The Aurora Borealis in the Northern HemisphereAnd the Aurora Australis in the Southern Hemisphere
29 Bellwork: Wednesday 5/23/2012 True / False. You can see magnetic fields without assistance.By looking at magnetic field patterns, you can tell where the magnetic forces are the strongest. Where are you looking and what do you see?You can tell by these lines whether the magnets are (A) attracting, or (B) repelling. What would each look like??—sketch and describe.False. Magnetic fields are invisible (until you use iron filings to help map them!).Magnetic force is strongest at the poles.Where all of the lines converge/intersectWhere the lines are most concentrated(A) Attracting- lots of lines connecting between them(B) Repelling- lines do not interact or touch—nothing observed between the magnets
30 Electricity/Magnetism Videos How Electricity is Created from Magnets9.15- Start 3.50 end 6.18Electricity_and_Magnetism__Current_Electricity 16.58Start .36 end 7.29
31 Energy Unit Test Corrections You only need ONE sheetUse an extra sheet of paper for more correctionsRest of classPlenty of time so EVERYBODY will be turning in test corrections.If you don’t turn them in – you will LOSE points!Weren’t actually two versions so…you can work with anybody!To do more test corrections, get on to the website at the top of the page to access the test.
32 Wednesday 5/23/12 Understanding Magnetism Video 50 minutes Complete ½ page quiz as you watch on pg. 3 in Packet 15