energy resources and energy transfer

4.8 explain how insulation is used to reduce energy transfers from buildings and the human body.

An insulator is something that is bad at conducting. If something with heat energy is surrounded by an insulator, it wont lose heat by conduction. This is true in buildings where insulating materials are put in walls and on floors to stop heat being lost from inside. This is the same in humans where we wear clothes to stop heat being lost from conduction. Air is a poor conductor, so materials with many air gaps in are also poor conductors; air trapped between double glazing prevents heat loss through windows.

4.6 describe how energy transfer may take place by conduction, convection and radiation

Conduction is when energy is passed from one particle to another via contact. For example heat is passed from your skin to a window when they touch. Convection is when particles with energy rise, the space they leave is filled by other particles. If the source of energy continues these new particles will also gain energy, they will then rise and the process will be repeated. Radiation is when heat is transferred as infra red waves. These waves can travel through space and be conducted or reflected. These energy transfers are all for heat energy.

4.7 explain the role of convection in everyday phenomena

Convection is helpful as it distributes heat energy. This is useful in many situations, for example, a radiator in one place will be able to heat a whole room, as hot air will rise away from it creating a current of cool air to be heated.

4.2 describe energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)

Energy can change from one form to another, and frequently does. Some examples include: Chemical energy in food turns into kinetic energy for movement; Electrical energy in a circuit turns into heat energy in a resistor; Kinetic energy in your muscles turns into sound energy from you voice. Elastic potential energy in a taught rubber band turns into kinetic energy when it sails through the air.

4.3 understand that energy is conserved

Energy can never be lost, only transferred. Energy will always carry on, just in a different form. For example, when you switch on a light, you are not loosing energy from a battery (chemical), you are just converting it to light energy!

4.5 describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship, including their representation by Sankey diagrams

With all devices that aim to use energy for a reason, some of the energy put in to run it comes out as a non useful form of energy. The more energy that comes out as useful, the more efficient the object is. For instance, a light bulb wants to create light energy, but it creates heat at the same time. This is the same for many processes: a fire (for warmth) creates light; a pepper grinder creates sound (even though you just want it to move). Sankey diagrams use an arrow to represent the energy going in and out of a process:

4.4 know and use the relationship: total energy input useful energy output efficiency

useful energy output / total energy input= efficiency

4.1 use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s), watt (W).

work done = force × distance moved W = F × d