2.2.4 AC & DC

• Direct Current (DC)


  A type of electrical current that flows in one constant direction
• Direct Current (DC)

  • Electrons move steadily in a single direction from the negative to the positive terminal
  • Voltage remains constant over time
• Alternating Current (AC)


  A type of electrical current that periodically reverses direction
• Alternating Current (AC)

  • Electrons periodically change direction
  • Voltage varies with time, typically following a sinusoidal wave
• Key Differences

  • Direction of Current
  • Voltage
  • Waveform
  • Frequency
• DC flows in a single direction
• AC reverses direction periodically
• DC voltage remains constant
• AC alternates between positive and negative values
• DC appears as a flat, constant line in a voltage-time graph
• AC appears as a wave in a voltage-time graph, often sinusoidal
• DC has no frequency since the direction of flow does not change
• AC has a frequency, measured in Hertz (Hz)
• In the UK, the standard frequency for AC is 50 Hz
• Applications of Direct Current (DC)

  • Batteries
  • Electronics
  • Solar Panels
• Applications of Alternating Current (AC)

  • Household Power Supply
  • Electric Grids
  • Electrical Appliances
• Advantages of Direct Current (DC)


  • Stability
  • Efficiency
• Disadvantages of Direct Current (DC)


  • Transmission
• Advantages of Alternating Current (AC)

  • Transmission
  • Versatility
• Disadvantages of Alternating Current (AC)

  • Complexity
• AC can be easily transformed to different voltages using transformers
• Rectifiers are used to convert AC to DC for applications that require a stable voltage
• High-voltage AC can be more dangerous due to its ability to cause more severe electric shocks compared to DC
• Summary of Key Points

  • DC flows in one direction
  • DC voltage remains constant
  • DC used in batteries, electronics, and solar panels
  • AC reverses direction periodically
  • AC voltage varies in a sinusoidal wave
  • AC used for mains electricity, power transmission, and household appliances
• Understanding AC and DC is essential for comprehending how electricity is used in different contexts and how electrical systems are designed and operated