Calculating Power

• What is the definition of power?

  Rate at which energy is transferred
• What is the formula for power using energy transferred?

  Power = energy transferred / time
• What is the formula for power using work done?

  Power = work done / time
• What is the unit for power?

  Watt
• How is one watt defined?

  One Joule per second of energy transfer
• How do you calculate the power of a bunson burner transferring 250,000 Joules in 500 seconds?

  • Power = energy transferred / time
  • Power = 250,000 J / 500 s
  • Power = 500 Watts
• How do you calculate the power of a bunson burner transferring 180,000 Joules in 500 seconds?

  • Power = energy transferred / time
  • Power = 180,000 J / 500 s
  • Power = 360 Watts
• If 40,000 Joules of work is done in 5 seconds, what is the power of the brakes?

  8,000 Watts
• How do you calculate the power of Motor A transferring 500 Joules in 40 seconds?

  • Power = energy transferred / time
  • Power = 500 J / 40 s
  • Power = 12.5 Watts
• How do you calculate the power of Motor B transferring 500 Joules in 60 seconds?

  • Power = energy transferred / time
  • Power = 500 J / 60 s
  • Power = 8.3 Watts (to one decimal place)
• What is the relationship between work done and energy transferred?

  Work done calculates energy transferred by force
• How does the power of two bunson burners compare if one transfers 250,000 Joules and the other 180,000 Joules in the same time?

  The first has higher power than the second
• What is the power output of a motor that transfers energy over a longer time?

  It will have lower power output