Reducing unwanted energy transfer

Lubrication reduces frictional forces

Whenever something moves, there’s usually at least one frictional force acting against it. This causes some energy in the system to be dissipated, e.g. air resistance can transfer energy from a falling object’s kinetic energy store to its thermal energy store.

For objects that are being rubbed together, lubricante can be used to reduce the friction between the object’s surfaces when they move. Lubricants are usually liquids(like oil), so they can flow easily between objects and coat them.

Insulation reduces the rate of energy transfer by heating

There are a few things you can do to prevent energy lost:

Have thick walls that are made from a material with a low thermal conductivity. The thicker the walls and the lower their thermal heat conductivity, the slower the rate of energy transfer will be(so the building will cool more slowly).

Use thermal insulation, such as:

Have cavity walls, which are made up of an inner and outer wall with an air gap with air in the middle, this reduces the amount of energy transferred by conduction through walls.

Loft insulation can reduce convection currents.

Double-glazed windows-air gap between two sheets of glass to prevent energy transfer by conduction.

Draught excluders around doors and windows to reduce energy transfers by convection.

Investigate the effectiveness of materials as thermal insulators:

  1. Boil water in a kettle. Pour some of the water into a sealable container(e.g. a beaker and lid) to a safe level. Measure the mass of water in the container.

  2. Use a thermometer to measure the initial temperature of the water.

  3. Seal the container and leave it for five minutes. Measure this time using a stopwatch.

  4. Remove the lid and measure the final temperature of the water.

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

  6. Repeat, but wrap the container in a different material.

  7. You could investigate how the thickness of the material affects how good a thermal insulator it is.

    Results:

    You should find that the thicker the insulating layer, the smaller the temperature change of the water, and so the less energy is transferred. This means thicker layers make better thermal insulators.