2.3.1 Electrical Power

• Electrical power


  The rate at which electrical energy is transferred or used by a device
• Unit of power

  The watt (W)
• 1 watt is equal to 1 joule of energy transferred per second
• Power calculation using Voltage and Current

  P=V×I
• Power calculation using Current and Resistance

  P=I²×R
• Power calculation using Voltage and Resistance

  P=V²/R
• Calculating Energy Using Power

  E=P×t
• Energy

  The amount of electrical energy transferred, measured in joules (J)
• Energy measurement

  Also measured in kilowatt-hours (kWh)
• High Power Devices

  • Consume more energy in a given time
  • Examples include electric heaters, ovens, and washing machines
• Low Power Devices

  • Use less energy over time
  • Examples include LED light bulbs and phone chargers
• Power Ratings on Appliances

  Indicate the maximum power they consume
• Efficiency

  A measure of how much of the electrical power supplied to a device is usefully transferred to perform the desired work
• Formula for Efficiency

  Efficiency=Useful power output/Total power input×100%
• No device is 100% efficient
• Series Circuits

  • Total power supplied is the sum of the power used by each component
  • Each component receives the same current, but voltage is divided
• Parallel Circuits

  • Voltage across each component is the same
  • Total power is the sum of the power consumed by each component
  • Each component operates independently, total current is divided
• Electricity usage is often measured in kilowatt-hours (kWh)
• Choosing Appliances

  Consider both the power rating and the expected usage time to estimate energy consumption and cost
• Understanding electrical power helps in making informed decisions about energy use and appliance selection