Power

• Power


  The energy transferred per second
• The maximum power of the iron is 1960 W
• The iron transfers 1960 joules of energy every second on its maximum setting
• A microwave transfers 950 joules of energy every second
• Calculating power


  1. Energy transferred = Power (W) x Time (s)

  2. Power = Energy transferred / Time
• A charger transfers 240 joules in 40 seconds
• Calculating power using current and potential difference

  Power (W) = Potential difference (V) x Current (A)
• The potential difference of a laptop battery is 16 V
• The current through the laptop is 3 A
• The mains potential difference is 230 V
• The current for the TV is 2.5 A
• Power


  Measured in watts
• Energy


  Measured in joules
• Appliances


  • 200 W electric blanket
  • 2 kW fan heater
• A toaster transfers 96,000 J in 120 seconds
• A TV transfers 24,000 J in 600 seconds
• A 12V, 5 A light bulb
• A 230 V, 12 A heater
• Energy transferred


  Power is the energy transferred per second