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Capacitors PowerPoint Presentation

Capacitors

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Capacitors

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Presentation Transcript

  1. Capacitors

  2. First… How Does a Battery Work? • A chemical reaction formed in a “CELL”. Slow but constant discharge. • Kind of like an old person or turtle.

  3. A battery is essentially a can full of chemicals that produce electrons – electrochemical reaction.

  4. That’s why batteries can Sit on a shelf for years and Still have power ! So HOW does it work? Current Flow Negative Terminal Positive Terminal Electrons flow from the battery into a wire, and must travel from the negative to the positive terminal for the chemical reaction to take place. Electrons collect in the negative terminal A depletion of electrons is left on the positive terminal

  5. Getting back to business… What do we use capacitors for?! • Store whopping amounts of electrostatic energy • Used to oppose changes in circuit VOLTAGE • Deliver SMOOTH voltage throughout circuit, or holds up a voltage level (Prevents Voltage DIP)

  6. What do Capacitors look like? A family of capacitors…

  7. Do Not EVER, EVER, EVER, EVER, EVER FORGET THIS! • Never ever take your television set apart. EVER • Capacitors are a special LEGOS as they are the only electrical device we use that stores electrical energy • Like a Jack Rabbit or spring released all at once

  8. - - - + Neg. Charge + + - + - - + + - Circuit Pathway DANGER!!

  9. What is Capacitance? • Property of an electrical device that allows it to store an electrical charge. • Or…..A “mighty” electrical spring

  10. One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way, and can then release them later. Like a Water Tower

  11. The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge.

  12. Electrons on the Move

  13. The Electron Hole • A positive ion attracts negative electrons. (that’s why electricity flows – to +) • When an electron moves from its valance ring it leaves a “HOLE” • A negative electron tries to fill the void while another electron fills another “hole” • In a sense the “hole” moves

  14. Let’s Make a HOLE!!! This demonstration will….. • Explain why…….. • Electricity can travel so fast • How an electron hole forms • Capacitance and Potential Difference

  15. Pos. Side Neg. side Power Source Flow

  16. Pos. Side Neg. side Power Source Flow GAP Shortage of - Collection of -

  17. A Little History Franklins Great OOOPs…….

  18. Capacitor Symbols Fixed Non-Polarized Capacitor Fixed Polarized Capacitor Variable Capacitor

  19. Capacitor Design • Electrostatic Fields on the end of two plates separated by a dielectric material • Fixed and Variable design

  20. Plates of Electrons

  21. Types of Dielectric Materials • Air or Vacuum • Rubber • Oil • Paper • Mica • Glass • Ceramic • Discharge Factors • Area of the plates • Distance between plates • Materials separating plates

  22. Mad Dog Face Off - + Gap Wire or conductor Wire or conductor

  23. Really Mad Dog Face Off - + - + - + - + - + - + Capacitor Plate

  24. Charging & Discharging a Capacitor

  25. Two Huge plates separated by a dielectric….. Lightning as a HUGE Capacitor?

  26. How Big is BIG? • The coulomb is the international standard unit of electric charge, named after Charles-Augustin de Coulomb • 1 coulomb is the amount of electric charge transported by a current of 1 ampere in 1 second… • The amount of electrical charge in 6.241506×1018 electrons 6,241,506,000,000,000,000 • Capacitance is measured in Farads • Farad = amount of capacitance for which a potential difference of 1 volt results in a static charge of 1 coulomb • Or… the amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt.

  27. Obviously, it's impractical to use capacitors to store any significant amount of power unless you do it at a high voltage. 1 Farad = The amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt • A standard alkaline AA battery holds about 2.8 amp-hours. • That means that a AA battery can produce 2.8 amps for 1 hour at 1.5 volts. • There are 3,600 seconds in one hour. • To store one AA battery's energy in a capacitor, you would need 3,600s * 2.8A /1.5v = 6,720 farads!! Howstuffworks.com

  28. MacGyver at work

  29. MacGyvers First Name A little known fact is that MacGyver's first name is "Angus" (Scottish heritage). Real Name: Richard Dean Anderson

  30. Making a Capacitor Foil UP Sideways Cover Sheet • Cut Foil • Sandwich Paper • Charge {10 + sec.} • Measure w/ Meter set @ {Volts m200} • Average the Three Readings Plain Paper

  31. That’s All Folks

  32. Stun Gun vs Death Ray