Reducing Unwanted Energy Transfers

• Lubrication reduces frictional forces
• If something is moving, there is usually a frictional force acting against it= causes some energy to dissipate
• Objects which are being rubbed together = lubricants used to reduce the friction between them when they move.
• Lubricants are usually liquids (oil) = flow easily between objects and coat them
• Insulation = reduces the rate of energy transfer by heating
• Prevent heat loss in houses:

→ Thick walls made from a low thermal conducting material = slow rate of energy transfer = cool more slowly

→ Thermal insulation:

1. Cavity walls (made up of an inner and outer wall with an air gap in between) = reduces the amount of conduction through the walls. Cavity insulation (cavity wall air gap is filled with foam) = reduce energy transfer by convection

2. Loft insulation = reduce convection currents

3. Double – glazed windows = have an air gap between two sheets of glass = prevent energy transfer by conduction

4. Draught excluders = reduce energy transfers by convection

• Practical to investigate the effectiveness of materials as thermal insulators:

1. Boil water and pour some into a sealable container. Measure the mass

2. Measure the initial(starting) temp of the water using a thermometer

3. Seal container and leave for 5 minutes using a stopwatch

4. Remove lid and measure the final temp

5. Pour water away and allow the container to cool so it goes to room temperature

6. Repeat but wrap the container in different materials once it has been sealed. It is important to use the same mass of water at the same initial temperature

7. Lower temp difference = better the material is as a thermal insulator

8. could also investigate how the thickness of a material affects how good a thermal insulator it is. Thicker = smaller temp change = less energy transferred= better thermal insulators