Unit 35 Magnetism And Magnetic Fields

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Unit 35 Magnetism And Magnetic Fields

  1. 1. Unit 35Magnetic Forces and Fields<br />
  2. 2. It is a substance that contains a magnetic field.<br />There are three primary types of magnets; <br />Ferromagnetic- A substance that is naturally and permanently magnetic like iron.<br />Paramagnetic- which becomes magnetic under the influence of a magnetic field.<br />Electromagnet- Becomes magnetic under the influence of an electric current. Is no longer magnetic when electricity flow is stopped.<br />What is a magnet?<br />
  3. 3. Magnetic Forces and Fields<br />Magnetic field =surrounds a magnet and can exert magnetic forces.<br />Magnetic force =the force a magnet exerts on another magnet, on iron, or a similar metal, or on moving charges (magnetic force is one aspect of electromagnetic force)<br />
  4. 4. Magnetic field =surrounds a magnet and can exert magnetic forces.<br />Fig. 35.1.1. Magnetic field lines – single magnetFig. 35.1.2. Magnetic field lines – two magnets<br />Iron filings lining up along the magnetic field<br />
  5. 5. A permanent magnet is a substance that holds a magnetic field indefinitely.<br />Iron, Cobalt, and Nickel are the only substances that are naturally magnetic.<br />But, Co and Ni are somewhat rare, so the vast majority of magnets are made of iron.<br />Permanent Magnet<br />Euro pennies have steel<br />
  6. 6. Electromagnetic devices:<br />An electromagnet starts with a power source and a wire. <br />Batteries/Electricity produce electrons. <br />Flowing electrons produce an electric field, which induces a magnetic field.<br />Electromagnetic devices are used to change electrical energy into mechanical energy.<br />Examples of electromagnetic devices: electric motors, galvanometers, loud speakers. <br />
  7. 7. Electromagnets can easily be made at home with a copper wire, a nail, and a battery.<br />Wrap the wire around the nail and hook it to the positive and negative ends of the battery.<br />Suddenly the nail is magnetic and can attract iron objects. <br />Electromagnets<br />
  8. 8. SOLENOID<br />Fig. 35.2.2. Solenoid<br />A magnetic field in a current carrying wire can be increased by wrapping the wire into a coil. This coil of wire is called a solenoid<br /> When a magnetic core is placed in a solenoid, an electromagnet is formed<br />This is the basis of many electric motors.<br />
  9. 9. Magnetic Poles<br />The magnetic field is a dipole field. That means that every magnet MUST have two poles, a positive (+) or negative (−) electrical charge (a north and a south pole).<br />Electrical charges are called monopoles, since they CAN exist without the opposite charge.<br />
  10. 10. Hans Christian Oersted<br />He discovered the connection between electricity and magnets by chance in 1820.<br />As he prepared for one of his classes, he noticed that when he turned on the electric current in a wire, a compass needle that was on another experiment changed its position. <br />When the electric current was turned off, the compass needle returned to its original position.<br />
  11. 11. Right Hand Rule<br />This magnetic field forms circles around a straight wire carrying the current. <br />Point your thumb in the direction of the current (which is toward the negative terminal) <br />If you curl your fingers around the wire, the way your fingers curve is in the direction of the magnetic field. <br />
  12. 12. Electric Generator (Dynamo)<br />The opposite of an electromagnet is also true also!<br />When a magnetic field rotates around a wire, it generates an electric current. <br />A hand-cranked dynamo charges a battery for an emergency radio…<br />Or you can have a hamster do it<br />
  13. 13. Turbines<br />Use water or wind to turn magnets to generate electricity<br />
  14. 14. Turbines<br />Closed-cycle pressurized water turbines<br />
  15. 15. To summarize<br />An electric current flowing around a rod will make a magnet.<br />It is called an electromagnet<br />A moving magnetic field flowing around a wire will make electricity.<br />It is called a generator<br />
  16. 16. Electricity and magnetism are both aspects of A. the north pole. <br />B. the south pole. <br />C. electromagnetic force. <br />D. ferromagnetic material.<br />Quick Quiz<br />
  17. 17. Electricity and magnetism are both aspects of A. the north pole. <br />B. the south pole. <br />C. electromagnetic force. <br />D. ferromagnetic material.<br />When electric charges are moving through a wire, a magnetic field is created. The wires are made out of materials/metals that can be magnetized. <br />Quick Quiz<br />
  18. 18. A fan uses a rotating electromagnet to turn its blades. This is an example of <br />A. magnetic poles. <br />B. an electric motor. <br />C. a galvanometer. <br />D. a loudspeaker.<br />Quick Quiz<br />
  19. 19. A fan uses a rotating electromagnet to turn its blades. This is an example of <br />A. magnetic poles. <br />B. an electric motor. <br />C. a galvanometer. <br />D. a loudspeaker.<br />Quick Quiz<br />
  20. 20. A material such as iron that can be magnetized because it contains magnetic domains.<br />Ferromagnetic material <br />
  21. 21. A substance that reacts to magnetic fields, but does not remain so after the field is removed.<br />Liquid Oxygen can remain suspended between two magnets.<br />Paramagnetic material<br />
  22. 22. Earth as a magnet<br />The Earth acts as a giant electromagnet. <br />There is a swirling liquid iron-nickel outer core floating around a solid iron-nickel inner core. <br />Electrons moving around in the liquid create an electric current.<br />
  23. 23. Earth as a magnet<br />The moving current around the iron core makes for a giant magnetic field.<br />This acts much like a magnet flowing around a wire, creating a strong magnetic field<br />
  24. 24. Earth’s Magnetic Field<br />The Earth’s magnetic field protects us from harmful solar particles by deflecting or absorbing them.<br />The aurora borealis is located at the north pole, because that is where the energized solar particles come shooting down into the atmosphere.<br />
  25. 25. Aurora Borealis<br />

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