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Electronic Technology
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  • Group Challenge: arrange yourselves into the electrical configuration of a doorbell. Parts needed: button/switch, battery, magnet, solenoid, gong, hammer/armature, spring & wires
  • STATOR "stays there" and ROTOR "rotates"
  • Review: Stator = permanent magnets, don't move Rotor = rotating armature (electromagnet, brush & split right commutator)
  • Review: Stator = permanent magnets, don't move Rotor = rotating armature (electromagnet, brush & split right commutator)
  • Brushes usually made of carbon - When the brushes reach the gap in the commutator, the circuit is broken, removing the magnetic field. - As it rotates further, the "other side" of the ring makes contact, switching the electromagnetic field of the rotor
  • What real motors look like.
  • Mary-go-round illustration: One person pushing a mary-go-round just once per rotation will result in a choppy spin that accelerates and slows according to when the push is given. However, if 8 people were positioned around the carousel to keep it going, the rotation would be much smoother.
  • A photograph of Michael Faraday , Thomas Henry Huxley , Charles Wheatstone, David Brewster and John Tyndall . Michael Faraday & Joseph Henry were the first to PROVE this connection

Electronic Technology Presentation Transcript

  • 1. Electronic Technology
  • 2. Magnetism Review
    • What 3 common metals have the greatest magnetic permeability?
    • Name 3 examples of permanent magnets. (shape & material)
    • Name 2 types of temporary magnets.
    • Describe the domains of a magnet.
    • What is the only naturally-occurring magnet found in the Earth's crust?
    • What type of "magnet" is responsible for Earth's magnetic field?
    • Describe Earth's core.
    • iron, nickel & cobalt
    • ceramic bar, flexible & flat fridge magnet, neodymium disc
    • induced paper clip, electromagnet
    • aligned (same dir.)
    • lodestone
    • "dynamo" electromagnet
    • solid iron inner core, surrounded by swirling liquid iron
  • 3. Magnetism Review
    • What word is used to describe Earth's magnetic pole's angle of variation from the geographic poles?
    • Describe the shape and polarity of Earth's magnetosphere.
    • True or False: The strength and location of Earth's magnetic poles constantly change; there's even evidence they've been reversed in the past.
    • Why is the magnetosphere important?
    • What do magnetic storms do?
    • Name 5 devices that use electromagnets .
    • declination
    • geographic north is magnetic south, sun-side is "squashed"
    • true
    • solar wind protection
    • heat/distort atmosphere
    • MRI, hairdryer, car door locks, speaker, maglev train, crane, electric toothbrush, toys, etc.
  • 4. Magnetism Review
    • Every wire carrying electricity has a weak around it.
    • What does the "right-hand rule" show us?
    • How does looping a wire carrying electricity affect the magnetic field around it?
    • What is a coil of current-carrying wire called?
    • What is created by running electric current around a magnetic material?
    • How does reversing the flow of electrons in a current affect the magnetic field?
    • What could you adjust to make a stronger electromagnet?
    • magnetic field
    • direction of current & flux
    • strengthens it
    • solenoid
    • electromagnet
    • reverses poles
    • more current, more/neater coils, better core material, lower temperature
  • 5. Electric Motors
    • An electric motor converts electricity into mechanical motion.
      • Most electric motors are rotary, producing rotational movement (spin, like a fan or turn of a wheel).
    • Stator: the stationary part
      • usually a permanent magnet
      • surrounds the rotor
    • Rotor : the rotating part
      • usually on the inside
      • contains an electromagnet attached to a frame called the armature
  • 6. Creating Motion from Electricity
    • Permanent magnets attract opposite poles of the electromagnet inside, causing it to rotate
    • Turn the electromagnet off momentarily & momentum will keep it turning
    • Then switch the poles of the electromagnet and the stationary magnets pull again, continuing the motion
    Electromagnet (coils not pictured) N S
  • 7. Motion from Electricity N S N S 3. Reversed poles of electromagnet, continue motion 2. Momentum keeps it turning when switched off 1. Stator magnets attract opposite poles of the electromagnet N S
  • 8. Rotor Assembly
    • Armature (inner rotating part)
      • battery supplies current
      • two brushes (connectors)
      • commutator
        • gaps stop current flow
        • rotation switches poles
      • solenoid
        • (many coils)
      • solid iron core
        • (not pictured)
    electro-magnet N S split ring commutator brush
  • 9. The Simple DC Motor
    • The force applied to the armature by the stationary magnetic field which causes it to rotate is called torque .
  • 10.  
  • 11. Multiple-Electromagnet Motors
    • Most motors have more than one magnet in the armature to assure smooth rotation.
  • 12. Pioneering scientists wondered...
    • If electrical currents can produce a magnetic field, can magnetic fields also produce an electrical current?
    • What do you think?
    If moving electrons produce a "push" (magnetic field) then that same "push" applied to a wire should cause electrons to move!
  • 13.
    • How is this diagram different than a motor?
    A hand crank replaces the battery.
  • 14. Creating Electricity from Magnets
    • PhET Simulation
    • Pickup Coil tab
      • Dots moving in the wire represent electric current
        • the faster they travel, the greater the current
      • Reading the Field Meter
        • B (top measurement) gives the overall field strength.
        • G stands for Gauss, the SI unit of magnetic field strength
        • Bx & By give coordinates to graph the flux lines
        • Ө gives the angle (in degrees) of the magnetic lines of force
      • Yellow lines around bulb show electricity is generated
        • longer lines indicate more current
  • 15. Electromagnetic Induction
    • A changing magnetic field causes current to flow in a conductor
      • Mechanical energy (KE - the energy of motion) is converted into electricity
    • Current flows ONLY when the magnetic field changes
      • magnet moves
        • permanent magnet
      • poles are reversed
        • electromagnet
  • 16. Electric Generators
    • A generator is a device which produces current by electromagnetic induction.
      • magnetic forces push electrons through a wire
      • opposite process of a motor
      • requires external energy source
  • 17. Hydroelectric Generator Nuclear Power Generator Human-Power Generator Wind Turbine Generator Steam Turbine Generator