MAGNETIC ATTRACTION Spring 2008 The Nature of Magnetism Magnets are found everywhere…doorbells, TV’s, computers… Magnets were discovered in a region

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  • MAGNETIC ATTRACTIONSpring 2008

  • The Nature of MagnetismMagnets are found everywheredoorbells, TVs, computersMagnets were discovered in a region in Greece called.you guessed itMagnesia!!!They discovered the unusual rock about 2,000 years ago.

  • The Nature of MagnetismThe rock had strange propertiesIt attracted anything that contained iron. This rock is the mineral we call magnetite. Magnetism is defined as the attraction of a magnet to another object. About 1,000 years agopeople discovered that magnets have another unusual property

  • The Nature of MagnetismIf you swing a rock freely from a stringone part of the rock always points in the same directiontoward a specific starnorthern star (also called the lodestar).For this reasonmagnetic rocks are sometimes called lodestones.

  • Magnetic PolesAny magnet has 2 ends each is a magnetic pole.This is the area where the magnetic effect is the strongestjust like one end of a magnetite rock always points on directionOne pole will always point north and therefore it is called the north pole. The other is, of course, the south pole. The north and south pole are direct opposites.

  • Attraction...What happens when you bring 2 magnets together?If you bring the 2 north poles together they repel or push away from each other. The same is true for 2 south poles.If you bring one north and one south pole together they are attracted to each other.Soalike poles repelunlike poles attract.Any material that exerts a magnetic attraction is considered a magnet.

  • So Whats the Big Deal??The Maglev Trainmagnetically levitating trainRuns solely on magnetismFast, efficient, and does NOT harm the environment

  • What happens if???What happens if you break a magnet? Do you get one south pole and one north pole magnet?Noactually when a magnet is broken in will develop another pole on that endso it will always have a north and a south end.If you break them againthe same process would happen.

  • MAGNETOThe character Magneto from the X-Men comic series has the ability to create magnetic fields and use magnetic force to control objects.

  • So, What are Magnetic Fields???Magnetic forces are exerted all around a magnet, but is strongest at the poles. The region of magnetic force around an object is called the magnetic field. A magnetic field allows magnets to interact without actually touching.

  • Magnetic FieldsMagnetic field lines map out the magnetic field around an object. These lines spread out from pole to pole and curve around the magnet to return to the other pole. See the diagram at left.

  • Magnetic PropertiesDepend on the structure of the atoms making up the object.A spinning electron (negatively charged) creates a magnetic field. A bar magnet has what is called a magnetic domain. It has a strong representation and therefore a stronger attraction. Materials that have a very strong attraction to a magnet are said to be ferromagnetic material. These are items made from iron, nickel, cobalt, samarium, etc.

  • Creating MagnetsYou can make a magnet by taking ferromagnetic material and place it in a magnetic field or rub a magnet against it. The field has to be relatively strong for this to occur.Once the domains line up your magnet is created. This is why you can magnetize a paperclip to pick up other paperclips. Unfortunately, most of theses are only temporary. Permanent magnets are much more difficult to make and hold their magnetism indefinitely

  • Destroying MagnetsYou can destroy a magnet field by striking the magnet very hard or dropping it as well. This knocks the domains out of alignment. Heating a magnet will also destroy the magnetism. Above a certain temperature, materials lose their ferromagnetism properties altogether.

  • CompassDefined as a device that has a magnetized needle than can spin freely. The needle usually points north. This occurs because the Earth acts like a giant magnet. Earth has an enormous magnetic field surrounding it just like a huge bar magnet. A scientist named Gilbert believed the center of the Earth contained magnetic rocksunfortunately, he was wrong, but it was a great start.

  • More on CompassesScientists now know that the magnetism is partially caused by the circulation of molten material made from iron and nickel. The simple fact that Earth has a magnetic field explains why a compass actually works. The magnetized needle aligns its domain with that of the Earth therefore pointing North.

  • MagnetosphereEarths magnetic field extends into space. Electrically charged particles affect Earths magnetic field.The Van Allen Belts are located about 1,000-25,000 km above the Earths surface. In this particular region, electrons and protons move at very high speeds.

  • MagnetosphereSolar Winds from the sun also carry electrically charged particles to Earth. The region where Solar Winds shape Earths magnetic fields is called the magnetosphere. This is a continual process as Earth rotates on its axis. When the particles move too close to Earths surface, we see the Aurora Borealis or Northern Lights in the sky. (called the Southern Lights in the Southern hemisphere)

  • Earths Magnetic FieldEarths magnetic directionality has changed throughout history.From time to timethe poles will switch due to the magnetic field created by the Earth.The last time the poles switched was about 780,000 years ago.Scientists are perplexed as to why this occurs, but believe it has something to do with the change in flow of the magnetic molten material at Earths core.

  • Its Electric!Electrons carry a negative charge. Protons carry a positive charge. When these charges flow through a wire or other object the create an electric current.Electric currents are defined as the flow of a charge through a material. The amount of charge that passes through the wire in a unit of time is measured in amperes (an amp).

  • Its Electric!An electric current produces a magnetic field. The direction of the current determines the direction of the magnetic field. If the current reverses, so does the field.

  • Electric CircuitsElectric currents do not automatically flow through wires. Current only flows through electric circuits.An electric circuit is a complete path through which electric charges can flow. All electrical devices contain electric currents.

  • Electric CircuitsAll circuits have the same basic features.A circuit has to have a source of electrical energy.Next, circuits have devices that are run by electrical energylike a light bulb converts electrical energy to electromagnetic energy (it gives off light) and thermal energy (it gives off heat). Lastly, electric circuits are connected by conducting wires and a switch.

  • ConductorsElectric currents do not flow through all objects.Electric currents move freely through objects called conductors. Examples of conductors: copper, silver, iron, and aluminum are all good conductors. In a conductor, some of the electrons are only loosely bound to their atoms. These electrons are able to move around and generate an electric current.

  • Light switch???Did you ever wonder why a light comes on when you flip a switch?Electrons are not created every time you flip a switch they are always there in the conductors of the circuit.

  • InsulatorsInsulators are a different kind of material where charges are not allowed to move freely. The electrons are bound tightly to their atoms and do not flow easily. Examples of good insulators: rubber, glass, sand, plastic, and wood.

  • Electrical ResistanceA resistor uses electrical energy as it interferes with, or resists, the flow of charge. Resistance is the opposition to the movement of charges flowing through a material.Resistance depends on an objects atomic structure. (Like trying to cross a crowded roomthe more collisionsthe more energy is converted.)

  • Light BulbEdison used resistance when developing his light bulb. He needed a material that conducted electrical currents, but that would offer enough resistance to make the material heat up and glow. He tried a variety of items: copper wires, silk fibers, shredded corn husks to name a few. He eventually used the metal tungsten for the purpose.

  • SUPERCONDUCTORS!!!A superconductor is a material that has no electrical resistance. This normally occurs at very low temperatures. (Thats the problem!)There is no loss of energy and therefore the electrical device is much more efficient. They also strongly repel magnets. A strong magnetic field would destroy a superconductor.

  • Electric MotorsDevice that changes electrical energy into mechanical energy. All electric motors have an armature a loop or coil of wire that can rotate. Armatures are mounted between the poled of an electromagnet. A Commutator reverses the current.

  • Electricity from Magnetsim

    Galvanometers - device that measures currentRuns by using an electromagnetHans Christian Oersted discovered that an electric current could make a magnetic field.Michael Faraday first to publish results in great detail. Electromagnetic induction electric current is made by changing a magnetic field.

  • Electric Current continuedAn electric current is created when a magnet moves in a coil of wire or when a wire moves between the poles of a magnet. Electric Generators uses electromagnetic induction to change mechanical energy into electrical energy. Electric generators generate alternating currents. Transformers increases or decreases voltage of an alternating current.

  • ElectromagnetsSolenoids is a current carrying wire with many loops.The solenoid creates a magnetic field at the center of the c