Electricity test

• all matter is made of atoms
• atoms contain protons, electrons and neutrons
• if an atom has an unequal # of protons and electrons, it’s an electric charge
• total charge =# of protons + # of electrons
• pith ball electroscope


  device used to detect the presence of a charge on an object
• metal leaf electroscope


  device that can detect an electric charge
• neutral objects are attracted to charged objects
• charging friction


  transfer of electrons between 2 neutral objects by CONTACT
• electrostatic series


  list of materials arranged in order of their tendency to gain electrons.
• charging objects by conduction

  charging of an object by contact with a charged object
• charging by induction


  charging a neutral object without touching
• temporary charging by induction

  as a negative balloon is brought close to a neutral wall, it induces a charge separation
• conductors 


  materials that allow movement of electrons like metals, saltwater, silver, gold, earth
• applications of conductors

  electrical wiring, circuit boards, appliances
• insulators

  materials that prevent the flow of electrons like plastic, rubber, wood, glass
• applications of insulators


  protective coating around electrical wiring
• current electricity


  the steady flow of electrons (powers devices).
• electrons flow easily through conductors like copper, aluminum, silver, mercury, iron, platinum, nickel
• electric circuit


  a continuous path for electrons to flow. to make one, you need a source of electrical energy, a load and maybe a switch
• example of electrical circuit

  flashlight
• Ammeters are always connected in series
• electrical energy


  energy generated from electrical circuits in Joules, like batteries and electrical generating stations
• electrical cells


  devices that convert chemical energy into electrical energy. 2 or more makes a battery
• electrical cells contain 2 metal pieces, called electrodes. One electrode is negatively charged and one is positively charged.
• electrons flow from negative to positive terminals
• types of cells 


  primary and secondary
• primary cells


  can only be used once: zinc chloride, alkaline, lithium cells)
• secondary cells


  can be recharged: lead-acid batteries, nickel metal hydride
• fuel cell


  type of cell where there’s a supply of chemicals fed into a cell (hydrogen fuel cell: H + O = H2O)
• forms of electricity


  direct current and alternating current
• direct current


  electrons flow only in one direction
• alternating current 


  electrons move back and fourth (in homes)
• electric current


  rate of electron flow past a point in a circuit measured in Amperes (A)
• Calculating electric current


  I = Q/T current (A) equals amount of charge (C) over time (Seconfs)
• Static Electricity or Electrostatics


  Imbalance of electric charge on the surface of an object
• Current Electricity


  Controlled flow of electrons through a conductor
• Electrons flow easily through good conductors
• Examples of good conductors

  • Silver
  • Copper
  • Gold
  • Aluminum
  • Magnesium
  • Tungsten
  • Nickel
  • Mercury
  • Platinum
  • Iron
• Electric circuit


  Continuous path for electrons to flow

  
• Components needed for an electric circuit

  • Source of electrical energy (e.g. battery or wall outlet)
  • Load (device that transforms electrical energy)
  • Switch (controls flow of electrons)
  • Conducting wires (provide path for electrons)