DC and AC supply

• Direct current (DC)


  Current that only flows in one direction
• Alternating current (AC)


  Current that constantly changes direction
• The main benefit of using AC is that it's very easy to use a transformer to increase or decrease the potential difference
• In the UK, AC switches direction 50 times per second, so it has a frequency of 50 Hertz
• In the UK, AC has a potential difference of around 230 volts
• Oscilloscope trace of AC


  • Shows the potential difference rising and falling, indicating the current has gone backwards and forwards
  • The height of the peak tells the maximum potential difference, which is around 230 volts
• Oscilloscope trace of DC


  • The potential difference does not change
• Using an oscilloscope trace to calculate AC frequency

  1. Time between two consecutive peaks is one complete cycle

  2. Frequency is the number of cycles per second, calculated as 1 divided by the time for one cycle