Mains electricity

• Alternating potential difference


  A potential difference that continually reverses its direction

  
• Direct potential difference


  A potential difference that only acts in one direction

  
• Alternating current (ac)


  An electric current which flows consistently in one direction around a circuit

  
• Direct current (dc)


  An electric current that continually reverses direction and changes size

  
• Sources of ac (alternating current)

  Power stations, ac generators, dynamos

  
• Sources of dc (direct current)

  Cells, car batteries, solar cells, dc generators

  
• Mains electricity


  An ac supply of electricity which is generated in power stations or by renewable energy resources

  
• Domestic electricity supply


  The electricity that is delivered to houses

  
• 230 V


  The potential difference of domestic electricity supply in the UK

  
• 50 Hz


  The frequency of domestic electricity supply in the UK

  
• Frequency


  when used to describe electricity, it is the number of times that an ac current changes direction from positive to negative to positive again

  
• Hertz (Hz)


  The SI unit for frequency

  
• Pd (potential difference)-time graph

  A graph used to display the variance of potential with time for alternating and direct current

  
• Dc (direct current) on a pd-time graph

  Direct current produces a straight, horizontal line at a constant potential difference

  
• Ac (alternating current) on a pd-time graph

  Alternating current produced a curve which alternates between positive and negative potential differences