Energy conservation

• Energy cannot be created or destroyed
• Useful energy


  Energy transferred into an energy store that is wanted
• Wasted energy


  Energy that is not transferred to a useful energy store
• Energy transfer in a hairdryer


  1. Energy transferred by electrical current

  2. Transferred to thermal store of heater

  3. Transferred to kinetic store of fan

  4. Useful energy transfer to hair

  5. Wasted energy to surroundings and sound
• Not all energy is transferred usefully
• The energy that is spread out into the surroundings is dissipated energy
• Friction


  Energy transferred to the thermal store of the parts of the device and its surroundings
• Friction happens between moving parts of a device

  Causes energy to be wasted
• The effects of friction can be reduced
• Reducing friction


  1. Separate surfaces

  2. Place oil between surfaces (lubrication)

  3. Use insulation to reduce heating transfer
• A hot water tank is a store of thermal energy
• Insulation slows down the transfer of energy to the surroundings
• The kinetic store of the moving bristles of an electric toothbrush is an example of useful energy transfer
• The noise from the electric toothbrush is an example of wasted energy
• When you drop a bouncy ball, the first bounce is always lower than the height that the ball is dropped from
• Energy stored before the ball is dropped

  Potential energy
• Useful energy store as the ball falls

  Kinetic energy
• Wasted energy during the fall

  Sound energy