electricity

• Charge of an atom

  If it gains an electron or loses an electron
• Energy conversions


  • Types happening in each instance
• Conductors


  Allow current electricity to flow through them
• Conductors


  • Copper - excellent conductor, used in electric wires
• Insulators


  Do not allow current electricity to flow through them
• Insulators


  • Plastic - excellent insulator, covers electric wires
• Poor conductors


  Current electricity can flow through them, but not very well
• Static electricity


  Electricity not flowing in a circuit
• Current electricity

  Electricity flowing in a circuit
• Charging insulators (Charging by contact)


  1. Insulators don't allow current electricity to flow through them

  2. You can still charge insulators by rubbing them together

  3. Electrons transfer from one to the other

  4. The one that gets electrons becomes negatively charged

  5. The one that loses electrons becomes positively charged

  6. Electrons move, the protons never move
• Neutralizing charged insulators - earthing


  1. We use the earth (earthing) to neutralise charged insulators

  2. If the object is negatively charged, the electrons flow from the object to you, to the ground you stand on

  3. If the object is positively charged, electrons flow from the ground to you then to the object

  4. If you touch a charged insulator with your hand you neutralise the charges in that position (the charges become balanced again)
• Current

  The flow of electrons through a circuit
• Amperes


  The scale that indicates the value of the current flowing
• Potential Difference (Voltage)


  The pushing force from an electrical power source (battery) that makes electrons move through a circuit
• Potential difference (Voltage)


  Measured in Volts by Voltmeter
• Power sources


  • Batteries and cells are sources of potential difference - transfer chemical energy into electrical energy
  • The potential energy they create depends on the size of the battery
  • Have negative (-) and positive (+) poles
  • Electrons travel from (-) to (+) through the closed circuit
• Ammeters and voltmeters


  • Need to be connected the right way around (red to +, black to -)
  • The two must be placed in the circuit in different ways. Current must flow through an ammeter but voltmeter measures the difference between 2 points
  • Should not be used when reading exceeds the instruments scale
• Multimeters


  Can read both voltage and current, usually replace ammeters and voltmeters
• Resistance


  How difficult it is for a current to flow through an electrical component
• Conductors


  Allow the flow of electricity - low resistance
• Insulators


  Do not allow the flow of electricity - high resistance
• Resistance


  Measured by an ohmmeter in Ohms (Ω), the unit for resistance
• Multimeters


  Can also measure resistance
• Ohms Law


  Relationship between potential difference, current and resistance
• Effects of electricity


  • Heating - hair dryer, iron, hair straightener
  • Chemical effect - electroplating jewellery
  • Magnetic effects
• Electrical power: Rate at which electrical energy is transferred into another form of energy
• Electrical power rating


  All electrical appliances have an electrical power rating measured in Watts