Electricity

• Current (amperes)


  Flow of electric charge
• Current


  • Can only flow if there's a potential difference and a closed circuit
  • Same value at every part of a loop
• Ammeter


  Connected in series
• Potential difference


  Difference in energy that charge carries have between 2 parts of a circuit
• Voltmeter


  Connected in series
• In a fixed resistor


  Current and potential difference are directly proportional
• Steeper gradient


  Lower resistance
• Filament lamp (non ohmic)

  • Curved line due to delocalised electrons colliding in ionic lattice
  • More vibrations
  • Temperature increase
  • Larger current
  • Larger resistance
• Diode


  • Allows current to flow though one direction
  • High resistance opposite direction
• Series circuit


  • Potential difference is shared in all components
  • Current is same throughout
  • Total resistance= sum of resistors
• Parallel circuit


  • Potential difference at each branch= potential difference of battery
  • Current is split thru each branch
  • Adding resistors in parallel reduces resistance
• Thermistor


  Resistance decreases as temp increases
• LDR


  Resistance decreases as light intensity increases
• Alternating current


  • Comes from alternating potential difference which results in an alternating flow
  • Used in UK mains electricity supply
• Direct current


  • Comes from a direct potential difference which results in direct flow
  • Used by battery
• Live wire


  • Brown
  • Carries 230V alternating current
• Earth wire


  • Green/yellow
  • Safety feature
  • Carries current at an emergency which would cause a person to be in electric shock when touching it
  • Not needed for double insulated appliances
• Neutral wire


  • 0V
  • Completes circuit
• Fuse


  • Thin metal wire which melts when current is too high causing a fault
  • Calculated by P=VI