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Everyday Electricity


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Everyday Electricity

  1. 1. Everyday Electricity February 26th, 2009
  2. 2. Conductors in Electrostatic Equilibrium <ul><li>Electrostatic equilibrium </li></ul><ul><ul><li>When no net motion of charge is occurring within a conductor </li></ul></ul><ul><ul><ul><li>Electrical field is 0 everywhere inside conductor </li></ul></ul></ul><ul><ul><ul><li>Any excess charge resides entirely on the conductors outer surface </li></ul></ul></ul><ul><ul><ul><li>Electrical field just outside a charge conductor is perpendicular to the conductor’s surface </li></ul></ul></ul><ul><ul><ul><li>Charge tends to accumulate where the radius of curvature of the surface is smallest (sharp points) </li></ul></ul></ul>
  3. 3. Why does it matter? <ul><li>When a conductor is in electrostatic equilibrium charge will collect at the sharpest points </li></ul><ul><li>When enough </li></ul><ul><li>charge accumulates </li></ul><ul><li>it will suddenly </li></ul><ul><li>discharge </li></ul>
  4. 4. Van de Graaff Generator <ul><li>The top of the generator </li></ul><ul><li>is a sphere so that large </li></ul><ul><li>amounts of charge can </li></ul><ul><li>build up without discharging </li></ul><ul><li>(they would discharge if </li></ul><ul><li>there was a point on top) </li></ul>
  5. 5. Static Electricity & Lightning <ul><li>Lightning occurs because of a polarization of the storm clouds </li></ul><ul><li>The bottom of the cloud </li></ul><ul><li>develops an excess of </li></ul><ul><li>Negative charge </li></ul><ul><li>A positive charge is </li></ul><ul><li>then induced on the surface </li></ul><ul><li>of the earth </li></ul>
  6. 6. <ul><li>As the static buildup during the storm becomes stronger the electrical fields around the cloud become strong enough to ionize the air, making it able to conduct electricity (becomes a conductive plasma) </li></ul><ul><li>A lightning bolt begins when a step leader of excess electrons begin to move towards the ground. </li></ul><ul><li>These electrons push away even more electrons from the Earth’s surface causing more positive charge to build up </li></ul>
  7. 7. <ul><li>The built-up positive charge can begin to migrate upward forming a streamer. </li></ul><ul><li>When the streamer and step leader meet a complete path is formed and lightning can strike! </li></ul>
  8. 8. Lightning Rods <ul><li>Lightning rods are often attached to the tops of tall buildings </li></ul><ul><li>The rod is made of metal and then attached to a wire that is buried deep in the ground </li></ul><ul><li>This gives the lightning an easy path to the ground and it will avoid going through the building </li></ul>
  9. 11. The Leyden Jar <ul><li>Earliest form of a battery </li></ul><ul><li>Charged by static electricity </li></ul><ul><li>Leyden Jar Demonstration </li></ul>