direct and alternating potential difference

• • mains electricity is an ac supply
  • current is constantly changing in ac supply
  • alternating currents are produced by alternating voltages - positive and negative ends alternating
• • in the UK, the domestic electricity supply has a frequency of 50Hz and a voltage of 230V
• • batteries and cells supply direct current
  • direct current is a current flowing in the same direction and is created by a direct voltage