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


  A machine that can show the pattern of an electrical current
• An oscilloscope trace of AC

  Shows the potential difference rising and falling, indicating the current has gone backwards and forwards
• An oscilloscope trace of DC

  Shows the potential difference does not change
• Calculating the frequency of AC using an oscilloscope trace

  1. Time between two consecutive peaks = one complete cycle

  2. Frequency = 1 / time for one cycle