conservation of energy

• What type of light bulb is being phased out but can still be found in buildings?

  Incandescent bulb
• What type of light bulb is becoming increasingly popular in homes around the UK?

  LED bulb
• What does efficiency tell us about energy transfer in an appliance?

  Fraction of energy input transferred to useful forms
• What indicates an incorrect calculation of efficiency when expressed as a percentage?

  Efficiency value greater than 100%
• What form of energy do inefficient light bulbs primarily transfer electrical energy into?

  Thermal energy
• What is a key difference between LED bulbs and less efficient bulbs in terms of energy transfer?

  LED bulbs transfer less energy to thermal
• How can the loss of thermal energy to the air around the edges of a hob be reduced?

  Use a pan with a wider base
• How can the loss of thermal energy to the air at the surface of water being heated in a pan be reduced?


  Use a lid
• Why is an electric kettle more efficient than a hob and pan for heating water?

  Heating element is inside the water
• What does it mean for a material to have a lower thermal conductivity?

  Conducts heat less well
• What property of plastic makes kettles more efficient than metal pans?

  Lower thermal conductivity
• What are some ways to increase the efficiency of an energy transfer when heating water?

  • Use a pan with a wider base
  • Use a lid on the pan
  • Use an electric kettle (heating element inside the water)
  • Use a kettle made of plastic
• What does the thermal energy image of the poorly insulated building show?

  A lot of thermal energy passing through walls/windows
• What does the thermal energy image of the well-insulated building show?

  Much less thermal energy passing through
• What are the two main factors that affect how quickly a building cools down?

  Thermal conductivity of walls, thickness of walls
• What does a high thermal conductivity of a material indicate?

  High rate of energy transfer by conduction
• What are modern houses typically built from?

  External brick, internal Breeze block wall
• What lies between the external and internal walls of modern houses?

  A cavity
• What is the problem with walls built with high thermal conductivity?

  A lot of energy can transfer out
• Why do builders pack the cavity with insulating material?

  To reduce overall thermal conductivity
• By how much can insulating material reduce the thermal conductivity of a wall?

  Up to 10 times
• What is one way that thermal energy can escape besides the walls?

  Through the windows
• Why do single glazed windows lose a lot of thermal energy?

  Because they have high thermoconductivity
• Why do most houses now have double glazed windows?

  Lower thermoconductivity reduces thermal energy loss
• What characteristic of loft insulation helps reduce thermal energy transfer?

  Low thermal conductivity
• How can thermal energy loss through the roof be reduced?

  With Loft insulation
• What are two ways to reduce thermal energy transfer from a house?

  Low conductivity materials, thick walls
• What does cavity wall insulation do to the rate of thermal energy transfer?

  Reduces the rate