Calculating power

• Power


  The rate at which energy is transferred or the rate at which work is done
• Calculating power


  1. Energy transferred in joules divided by time in seconds

  2. Work done in joules divided by time in seconds
• Watt


  The unit of power, equal to an energy transfer or work done of one joule per second
• Calculating power of Bunsen burners

  • Left Bunsen burner: 250,000 joules of thermal energy transferred in 500 seconds, power = 500 watts
  • Right Bunsen burner: 180,000 joules of thermal energy transferred in 500 seconds, power = 360 watts
• Calculating power of car brakes

  • 40,000 joules of work done in 5 seconds, power = 8,000 watts
• Calculating power of motors

  • Motor A: 500 joules of electrical energy transferred to gravitational potential energy in 40 seconds, power = 12.5 watts
  • Motor B: 500 joules of electrical energy transferred in 60 seconds, power = 8.3 watts