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Bellwork: Monday 5/21/2012 1.What causes a compass to behave as it does? Earth’s gravity Earth’s shape Earth’s geographic north pole Earth’s magnetic.

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Presentation on theme: "Bellwork: Monday 5/21/2012 1.What causes a compass to behave as it does? Earth’s gravity Earth’s shape Earth’s geographic north pole Earth’s magnetic."— Presentation transcript:

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2 Bellwork: Monday 5/21/2012 1.What causes a compass to behave as it does? Earth’s gravity Earth’s shape Earth’s geographic north pole Earth’s magnetic field 2.Magnetic poles that are alike attract each other repel each other do not interact have the same shape 3.As in the case of unlike magnetic poles, unlike electric charges attract each other repel each other exist in pairs do not interact 1. Earth’s magnetic field…causes a compass to behave as it does 2. Magnetic poles that are alike…repel each other 3. Unlike electric charges...attract each other

3 Packet 16, Pg 1- History of Magnetism 2000+ years ago –Greeks near the city of Magnesia found strange and rare stones with the power to attract iron— called them magnetite (Fe 3 O 4 ) –Lodestone- naturally magnetized piece of magnetite 1000 years ago –Chinese 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.

4 Christopher Columbus- 1492 Used a compass when he crossed the Atlantic ocean His observations: –t–the compass needle strayed slightly from exact north as indicated by the stars –t–the variation changed during the voyage

5 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 ago William 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

6 Safety with Magnets Magnets should not be held near these things: –Credit cards –Magnetic I.D. cards –TV or VCR –Computer monitor –Floppy computer discs –Cassette Tapes/ Video Tapes –Tape Recorders –Radio –Any Speakers –A magnet will harm most electrical devices!!!

7 Using Magnetism for Evil?! Magneto is a powerful mutant with the ability to generate and control electromagnetic forces.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.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.Magneto has been the X- Men's most prominent enemy ever since his first appearance.

8 Magnetic Force 4.5- 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 materials –Force is stronger than gravitational force (allows us to pick up objects using a magnet ) Magnetic fields: –Can be mapped –More field lines indicates the strength of the magnet in that area –Strongest 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.

9 Properties of Magnets 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 other –Magnetic poles that are alike repel each other. –Magnetic poles that are different attract each other. S N SN SNSN

10 Magnetism Paramagnetism - When a paramagnetic material is placed near a magnet, it will be attracted to the region of greater magnetic field –Exhibited 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 field –Exhibited by: all common materials, but is very weak Ex. People, frogs Ex. Metals such as bismuth, copper, gold, silver and lead, as well as many nonmetals such as water

11 "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 midriff Since this "gift'' is also present in three of his sons and two grandchildren, he figures it's hereditary.

12 The boy with the magnetic personality May 11, 2011 Six-year-old Croatian, Ivan Stoiljkovic, can stick metal objects to his body such as: spoons, mobile phones and even frying pans Reality: 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.

13 3 Types of Magnets 1.Natural (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 times Earth produces a magnetic field due to molten iron in core and spinning of the earth Permanent magnets can be damaged from extreme heat and dropping

14 Permanent Magnets Each 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. Domains Lets melt the iron, and bring in a magnetic field. Now, 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. Temp Melting point Bar Magnet

15 3 types of magnets 2. Temporary Magnet- only have magnetic properties for a short period of time, after exposure to a permanent magnet Iron—composed of molecules (domains) –All different directions = no magnetic force or pull –All lined up in one direction = force to pull things towards them

16 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:An unmagnetized substance looks like: While a magnetized substance looks like: While a magnetized substance looks like:

17 How to demagnetize a magnet: 1. Impact (hit it) 2. Heat it This causes the domains to become random again! 3. Electricity

18 3 types of Magnets 3. 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.

19 Bellwork: Tuesday 5/22/2012 1.What happens if a magnet breaks in half? –One half has a north pole only, and one half has a south pole only –Neither half will have a pole –Each half will be a new magnet, with both a north and south pole –Neither half will attract or repel. 2.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). 3.The region around a magnet where the magnetic force is exerted is known as its –magnetic pole –magnetic field –magnetic domain 4.Magnetism can be considered a –nuclear property –physical property –chemical property 5.A temporary magnet –keeps its magnetism for a long time –cannot be destroyed –easily loses its magnetism Attract  Repel  SNSNSN

20 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.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.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.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 results in lower milk production (for dairy cattle) or lower weight gain (for feeder stock). This condition is called hardware disease.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. 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. 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! One small cow magnet can help a cow for her whole life!

21 Magnetic Fields- pg. 3 Procedure: 1.Place a magnet into a tray, put a piece of paper over the magnet. 2.Lightly sprinkle iron filings on and around the magnet, gently tap the paper. 3.Observe the formation around the magnets, and sketch what you see. Types of Demonstration: 1.One magnet 2.Two magnets- Attracting 3.Two magnets- Repelling

22 Mapping Magnetic Fields One Magnet Two Magnets- Attracting Two Magnets- Repelling NS NS NSSN NS

23 MAGNETIC FIELDS- One Magnet This picture demonstrates what occurs when one magnet is placed on paper, and iron filings are sprinkled around it.

24 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.

25 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 Like poles repel… Opposite poles attract!

27 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…

28 The Aurora Borealis in the Northern HemisphereAnd the Aurora Australis in the Southern Hemisphere

29 Magic of Magnets - 15 minutesMagic of Magnets Tuesday 5/22/12

30 Bellwork: Wednesday 5/23/2012 1.True / False. You can see magnetic fields without assistance. 2.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? 3.You can tell by these lines whether the magnets are (A) attracting, or (B) repelling. What would each look like??— sketch and describe. 1. False. Magnetic fields are invisible (until you use iron filings to help map them!). 2. Magnetic force is strongest at the poles. –Where all of the lines converge/intersect –Where the lines are most concentrated 3. (A) Attracting- lots of lines connecting between them (B) Repelling- lines do not interact or touch—nothing observed between the magnets

31 Electricity/Magnetism Videos How Electricity is Created from Magnets –9.15- Start 3.50 end 6.18 Electricity_and_Magnetism__Current_Elect ricity 16.58Electricity_and_Magnetism__Current_Elect ricity 16.58 –Start.36 end 7.29

32 Energy Unit Test Corrections You only need ONE sheet –Use an extra sheet of paper for more corrections Rest of class –Plenty 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.

33 Understanding Magnetism Video 50 minutesUnderstanding Magnetism Video –Complete ½ page quiz as you watch on pg. 3 in Packet 15 Wednesday 5/23/12


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