DC and AC supply

• What is another name for direct current?

  DC
• What is another name for alternating current?

  AC
• What does direct current (DC) mean?

  Current flows in one direction only
• What does alternating current (AC) mean?

  Current constantly changes direction
• How can you determine the features of an AC supply?

  Using an oscilloscope trace
• What is the frequency of AC in the UK?

  50 hertz
• What is the potential difference of mains electricity in the UK?

  230 volts
• Why is alternating current (AC) preferred for power transmission?

  It easily uses transformers for voltage changes
• How does the oscilloscope display alternating current?

  It shows rising and falling potential difference
• What does the height of the peak on an oscilloscope indicate?

  The maximum potential difference
• How do you calculate the frequency of an AC signal from an oscilloscope trace?

  Frequency = 1 / time for one cycle
• If the time between peaks is $0.02 \text{ seconds}$, what is the frequency?


  50 hertz
• What happens to the current in a direct current circuit?

  It only moves in one direction
• What does the term "cycle" refer to in AC?

  One complete change of direction
• What would you expect to see on an oscilloscope for direct current?

  A constant potential difference line
• What are the key features of direct current (DC) and alternating current (AC)?

  • DC: Current flows in one direction only
  • AC: Current constantly changes direction
• How do transformers relate to AC and DC?

  • AC: Easily transformed to change voltage
  • DC: Harder to transform for voltage changes
• What can you determine from an oscilloscope trace of AC?

  • Maximum potential difference
  • Frequency of the current
  • Pattern of current flow
• What are the expected values for mains electricity in the UK?

  • Frequency: 50 hertz
  • Potential difference: 230 volts