Topic 11 - Static Electricy

• Insulators


  Charged by friction
• Electrons


  Added or taken away
• Gaining electrons


  Results in a negative charge
• Losing electrons


  Results in an equal and opposite positive charge
• Like charges repel and unlike charges attract
• Protons do not move
• Large charges can attract and repel only the electrons, leaving the protons behind and inducing an opposite charge
• Demonstrating charge


  • Balloon (insulator)
  • Sweater
  • Wall
• Charging a balloon


  1. Rubbing insulator against sweater drags electrons

  2. Balloon moves towards wall

  3. Induces opposite charge

  4. Opposite charges attract
• Electrons rub onto balloon, sweater becomes positive, balloon becomes negative, they are attracted
• Moving balloon towards wall

  Pushes electrons away, leaving positive protons behind, opposite charges attract
• Shocks from everyday objects

  Caused by charge buildup and discharge
• Getting shocks when getting out of car

  1. Sliding across seat charges you and seat

  2. Charge leaves body into air

  3. If air is cold/dry, charge quickly leaves into metal, causing shock
• To prevent shocks, don't keep yourself isolated, touch metal on car
• Lightning


  Electrostatic phenomenon, small ice crystals build up charge, cloud becomes negatively charged, induces opposite charge in ground, spark jumps
• Electrostatic attraction


  • Balloon sticking to wall
  • Comb picking up paper
• Comb picking up paper

  1. Rub electrons onto comb with cloth

  2. Comb becomes negatively charged

  3. Induces positive charge in paper, opposite charges attract
• Electrostatic spraying


  Atomized droplets get negatively charged, attracted to target, coat entire object
• Electrostatic spraying is cheaper, more efficient, and more environmentally friendly than conventional spraying
• Static electricity can cause problems during aircraft and car refueling, wire connects tanker and plane, special tires conduct charge to ground
• Electric field lines


  Flow out from positive charge, in towards negative charge, perpendicular to plates, stronger field where lines are closer together