AC and DC current

• What are the two types of current that need to be known?

  Alternating current (AC) and direct current (DC)
• How does alternating current (AC) behave?

  The direction of the current constantly swaps back and forth
• What causes alternating current to fluctuate?

  It is caused by an alternating potential difference or alternating voltage
• What does measuring potential difference or current over time reveal about AC?

  It shows that they constantly fluctuate between negative and positive
• What type of current is supplied by UK mains electricity?

  Alternating current (AC)
• What is the frequency and voltage of UK mains electricity?

  50 hertz and around 240 volts
• What does the fluctuation of potential difference in UK mains electricity look like?

  It fluctuates from positive 240 volts to negative 240 volts
• How many times does the potential difference fluctuate in UK mains electricity every second?

  50 times every second
• Why might you hear that the voltage in the UK is 230 volts instead of 240 volts?

  Both 230 volts and 240 volts are correct as far as exams are concerned
• How does direct current (DC) behave?

  The charge always flows in the same direction
• Where do we commonly find direct current (DC)?


  In cells and batteries
• What devices are used to obtain potential difference time graphs?

  Oscilloscopes
• What are the key characteristics of alternating current (AC)?

  • Direction of current constantly swaps
  • Caused by alternating potential difference
  • Fluctuates between positive and negative
  • UK mains supply: 50 Hz, ~240 volts
• What are the key characteristics of direct current (DC)?


  • Charge flows in the same direction
  • Produced by a direct potential difference
  • Commonly found in cells and batteries