power and work done

• Power


  The rate at which energy is transferred
• Power


  The rate at which work is done
• Calculating power (energy transfer)

  Energy transferred / Time taken
• Calculating power (work done)


  Work done / Time taken
• Work done is a special measure of energy transferred when a force is used to move an object by a certain distance
• Energy transferred and work done are measured in joules, time is measured in seconds, and power is measured in watts
• Comparing two lamps


  • Lamp 1: 1200 joules over 20 seconds

  Lamp 2: 1500 joules over 30 seconds
• Lamp 1


  60 watts of power
• Lamp 2


  50 watts of power
• Lamps may have a label indicating their power
• Calculating power when 9 kilojoules of work is done over 20 seconds


  Work done / Time taken

  9,000 joules / 20 seconds

  450 watts