DC and AC Supply

• What does an oscilloscope do?

  It shows the pattern of electrical current
• What is current in an electrical circuit?

  A flow of electrons
• What direction does current from a cell move?

  In one direction
• What is the abbreviation for direct current?

  DC
• What is the abbreviation for alternating current?

  AC
• What is a key feature of alternating current?

  The current constantly changes direction
• What is the main benefit of using alternating current?

  Easy to use a transformer for voltage changes
• How many times does alternating current switch direction in the UK?

  50 times a second
• What is the frequency of alternating current in the UK?

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

  230 volts
• What does the height of the peak on an oscilloscope trace indicate?

  The maximum potential difference
• How does a direct current appear on an oscilloscope?

  The potential difference does not change
• How do you calculate the frequency of alternating current from an oscilloscope trace?

  Frequency = 1 / time for one cycle
• If one peak occurs at $0.01\text{ seconds}$ and the next at $0.03\text{ seconds}$, what is the time between peaks?


  $0.02\text{ seconds}$
• If each cycle takes $0.02\text{ seconds}$, what is the frequency?


  $50\text{ Hz}$
• What are the features of direct current (DC) and alternating current (AC)?

  • Direct Current (DC):
  • Flows in one direction
  • Current from a cell
  • Alternating Current (AC):
  • Changes direction constantly
  • Used in mains electricity
• What are the uses of an oscilloscope in electrical circuits?

  • Visualizes electrical current patterns
  • Measures potential difference
  • Calculates frequency of AC
• What are the key specifications of mains electricity in the UK?

  • Frequency: 50 Hz
  • Potential difference: 230 volts