Electricity

• describe current

  • flow of charge
  • only flows if there is a potential difference
  • in a single closed loop it is the same everywhere
• describe resistance

  • anything that slows flow
  • depends on whether the circuit is series or parallel
  • depends on length of wire
• what does an ammeter do ?

  calculates current
• what does a voltmeter do ?

  calculates potential difference
• what is an LDR ?

  • dependant on light intensity
  • bright light = less resistance
• what is a thermistor ?

  • temperature dependant
  • hot = low resistance
  • useful temperature detectors
• what is a series circuit ?

  components connected in a line
• what is potential difference like in a series circuit ?

  it's shared
• what is current like in a series circuit ?

  the same everywhere
• what is resistance like in a series circuit ?

  adds up to Total
• what is a parallel circuit ?

  components are on seperate branches
• what is potential difference like in a parallel circuit ?

  the same everywhere
• what is current like in a parallel circuit ?

  shared out
• how can you reduce resistance in a parallel circuit ?


  add a resistor
• what does energy transfer depend on ?

  power
• what is an alternating current ?

  when positive and negative constantly swap
• what current is UK mains ?

  alternating
• what is a direct current ?

  current is always in same direction
• what current do batteries have ?

  direct
• what is the blue wire in a plug ?

  • neutral wire
  • completes the circuit
• what is the brown wire in a plug ?

  • live wire
  • provides potential difference from mains supply
• what is the yellow & green wire in a plug ?

  • earth wire
  • stops appliance becoming live
  • obly carries current when it is needed
• what does a power station do?

  meet the demands of electricty during the day
• what are the stages of the national grid ?

  1. power station
  2. step up transformer
  3. step down transformer
  4. consumers
• what does a step up transformer do ?

  increase potential difference, increase current
• what does a step down transformer do ?


  decreases potential difference, current increased to ensure safety of consumer