Magnets electromagnets probe


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  • Magnets electromagnets probe

    1. 1. Radio conversation between two ships passing in the night... <ul><li>Voice 1 : &quot;We can see your lights and you are on a collision course with our vessel. Please divert your course 15 degrees to the North to avoid a collision.&quot; Voice 2 : &quot;I can see your lights too and recommend you divert your course 15 degrees to the South to avoid a collision.&quot; Voice 1 : &quot;This is the captain of a US Navy ship. I say again, divert YOUR course.&quot; Voice 2 : &quot;No, I say again, you divert YOUR course.&quot; Voice 1 : &quot;I am in the U.S.S. Wolverine, the largest battleship on this ocean. I DEMAND that you change your course one-five degrees North!&quot; Voice 2 : &quot;I am in the Point Amour lighthouse. Your call, sir.&quot; </li></ul>
    2. 2. Magnetism <ul><li>I. Characteristics of Magnets </li></ul><ul><li>(p.624-627) </li></ul><ul><ul><li>Magnetism </li></ul></ul><ul><ul><li>Magnetic poles </li></ul></ul><ul><ul><li>Magnetic field </li></ul></ul><ul><ul><li>Magnetic domain </li></ul></ul>
    3. 3. What are magnets? <ul><li>Magnets are metal objects that create magnetic fields and attract other objects containing iron, nickel or cobalt. </li></ul>
    4. 4. Properties of Magnets <ul><li>Attract iron, nickel and cobalt </li></ul><ul><li>Have magnetic poles </li></ul><ul><li>Exert magnetic forces </li></ul><ul><li>Surrounded by a magnetic field </li></ul><ul><ul><li>what else do we know that is surrounded by a field?? </li></ul></ul>
    5. 5. A. Magnetism <ul><li>Magnetism </li></ul><ul><ul><li>force of attraction or repulsion between unlike or like poles </li></ul></ul><ul><ul><li>due to the arrangement of electrons </li></ul></ul><ul><ul><li>closely related to electricity </li></ul></ul><ul><ul><li>The SI unit is tesla (T) </li></ul></ul>
    6. 6. Magnetic Poles <ul><li>The strongest force on a magnet is found at the ends of the magnet </li></ul><ul><li>The ends of the magnet are called the Poles </li></ul><ul><li>If you tie a string to a magnet, the part that is the “north” always points to the north pole of the Earth. </li></ul><ul><li>There are North and South poles on ALL magnets. </li></ul>
    7. 7. B. Magnetic Poles <ul><li>Magnetic Poles </li></ul><ul><ul><li>like poles repel </li></ul></ul><ul><ul><li>unlike poles attract </li></ul></ul><ul><ul><li>a broken magnet creates new poles </li></ul></ul>
    8. 8. Magnetic Forces <ul><li>This is the push or pull a magnet causes. </li></ul><ul><li>If two poles are the same they _______ </li></ul><ul><li>If two poles are opposite they _______ </li></ul><ul><ul><li>What have we talked about that also has forces that work this way? </li></ul></ul>repel attract electricity with electrons and protons
    9. 9. Magnetic Field <ul><li>The region around a magnet in which magnetic forces can act or are effective. </li></ul><ul><li>The magnetic field is strongest around the poles! </li></ul>
    10. 10. C. Magnetic Field <ul><li>Magnetic Field </li></ul><ul><ul><li>area around a magnet where magnetic forces act </li></ul></ul><ul><ul><li>field lines show direction of field (N  S ) </li></ul></ul>
    11. 11. D. Magnetic Domain <ul><li>Magnetic Domain </li></ul><ul><ul><li>groups of atoms with aligned magnetic poles </li></ul></ul><ul><ul><li>in a magnetized object, domains are all aligned </li></ul></ul>domain
    12. 12. All materials are not magnetic <ul><li>The atoms in matter cause magnetism </li></ul><ul><ul><li>All atoms have a north and south pole created by the movement of electrons. </li></ul></ul><ul><ul><li>In most substances the atoms are arranged such that the magnetic fields are canceled. </li></ul></ul><ul><ul><li>In other matter, like iron, nickel and cobalt, the atoms group together in regions called domains. These domains can become aligned. If most of the domains are aligned, the object becomes magnetic. </li></ul></ul>
    13. 13. <ul><li>Objects containing iron, nickel or cobalt can be magnetized by aligning the domains. </li></ul><ul><li>Magnets can lose magnetic properties if these atoms lose alignment </li></ul><ul><ul><li>By striking or dropping a magnet too hard </li></ul></ul><ul><ul><li>By heating a magnet to high temperatures </li></ul></ul><ul><li>You cannot have half a magnet. </li></ul>
    14. 14. Types of Magnets <ul><li>Ferromagnets </li></ul><ul><ul><li>Natural magnets made of iron, cobalt or nickel </li></ul></ul><ul><li>Electromagnets </li></ul><ul><ul><li>Usually with an iron core and made by an electric current </li></ul></ul><ul><li>Permanent </li></ul><ul><ul><li>Difficult to magnetize but retain properties </li></ul></ul><ul><li>Temporary </li></ul><ul><ul><li>Easy to magnetize but lose properties easily </li></ul></ul>
    15. 15. Earth as a Magnet <ul><li>The Earth acts as if it has a bar magnet running through it! </li></ul><ul><li>The geographic North Pole is the magnetic South Pole. </li></ul><ul><li>The Earth’s geographic </li></ul><ul><li>poles are on the axis </li></ul><ul><li>around which Earth spins. </li></ul><ul><li>The spinning of Earth’s </li></ul><ul><li>iron and nickel core causes alignment of electrons, thus the magnetic field. </li></ul>
    16. 16. Aurora <ul><li>The Aurora Borialis and Aurora Australis are “light shows” that are caused by charged particles from the sun interacting with our upper atmosphere. These are usually visible in the far north and south because this is where the magnetic field is dipping back into the earth. </li></ul>
    17. 18. Recap!! <ul><li>1) What are 4 magnetic properties? </li></ul><ul><li>2) How do magnetic forces interact? </li></ul><ul><li>3) Why are some materials magnets while others are not? </li></ul>
    18. 19. Magnetism <ul><li>III. Producing Electric Current </li></ul><ul><li>(p.633-639) </li></ul><ul><ul><li>Electromagnetic Induction </li></ul></ul><ul><ul><li>Electric Generator </li></ul></ul><ul><ul><li>DC & AC </li></ul></ul><ul><ul><li>Transformer </li></ul></ul>
    19. 20. Introduction to Magnetism from Electricity <ul><li>Ever heard of Maglev?? </li></ul>
    20. 21. Discovery of Electromagnetism <ul><li>Discovered by a man named Hans Oersted. </li></ul><ul><ul><li>His research concluded that an electric current produces a magnetic field in the direction of a given current </li></ul></ul><ul><li>Electromagnetism is the interaction between electricity and magnetism. </li></ul>
    21. 22. A. Electromagnetic Induction <ul><li>Electromagnetic Induction </li></ul><ul><ul><li>producing a current by moving a wire through a magnetic field </li></ul></ul><ul><ul><li>some microphones work just like mini-speakers in reverse </li></ul></ul><ul><ul><li>sound waves cause coil to move  current </li></ul></ul>Dynamic Microphone Coil
    22. 23. B. Electric Generator <ul><li>Electric Generator </li></ul><ul><ul><li>mechanical energy  electrical energy </li></ul></ul><ul><ul><li>armature is rotated between magnet poles </li></ul></ul><ul><ul><li>magnetic field induces a current in the wire coil </li></ul></ul>MOTOR GENERATOR
    23. 24. B. Electric Generator <ul><li>Hydroelectric Dam </li></ul><ul><ul><li>PE of lake water is converted to KE </li></ul></ul><ul><ul><li>mechanical KE turns the generator shaft which creates electrical energy </li></ul></ul>
    24. 25. C. DC & AC <ul><li>Direct Current (DC) </li></ul><ul><ul><li>current flows in one direction </li></ul></ul><ul><ul><li>dry cells </li></ul></ul><ul><li>Alternating Current (AC) </li></ul><ul><ul><li>current reverses its direction at regular intervals </li></ul></ul><ul><ul><li>electrical outlets </li></ul></ul>
    25. 26. D. Transformer <ul><li>Transformer </li></ul><ul><ul><li>increases or decreases AC voltage </li></ul></ul><ul><ul><li>primary coil AC produces a magnetic field that induces AC in the secondary coil </li></ul></ul><ul><ul><li>voltage ratio = ratio of turns in each coil </li></ul></ul>
    26. 27. D. Transformer <ul><li>Step-up Transformer </li></ul><ul><ul><li>increases the voltage </li></ul></ul><ul><ul><li>more turns </li></ul></ul><ul><ul><li>power plants </li></ul></ul><ul><li>Step-down Transformer </li></ul><ul><ul><li>decreases the voltage </li></ul></ul><ul><ul><li>fewer turns </li></ul></ul><ul><ul><li>household appliances (hairdryers, etc.) </li></ul></ul>
    27. 29. Magnetism <ul><li>II. Uses of Magnetic Fields </li></ul><ul><li>(p.628-632) </li></ul><ul><ul><li>Electromagnet </li></ul></ul><ul><ul><li>Speaker </li></ul></ul><ul><ul><li>Motor </li></ul></ul>
    28. 30. Electromagnet <ul><li>Electromagnet </li></ul><ul><ul><li>strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core </li></ul></ul><ul><ul><li>acts like a bar magnet when current is on </li></ul></ul>
    29. 31. Speaker <ul><li>Speaker </li></ul><ul><ul><li>electrical energy  mechanical energy </li></ul></ul><ul><ul><li>wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet </li></ul></ul><ul><ul><li>forced vibration causes the cone to move  sound </li></ul></ul>
    30. 32. Video
    31. 33. Motor <ul><li>Motor </li></ul><ul><ul><li>electrical energy  mechanical energy </li></ul></ul><ul><ul><li>electromagnet rotates between the poles of a fixed magnet </li></ul></ul><ul><ul><li>commutator reverses the poles of the e’magnet </li></ul></ul>
    32. 34. Motor brushes & wires to battery field magnet armature & commutator assembled motor