The energy transferred in this picture is…….

Learning objectives

• Describe the energy transfers in a range of devices.

• Identify where energy is wasted.

• Explain why wasted energy is difficult to use.

Forms of energy

click

Forms of energy

• Energy is needed to keep us working, and to operate all the machines around us.

• Different forms of energy include…..

•

Light, sound, electrical, potential and kinetic energy

.

• Energy can also be stored.

Nuclear energy

is stored inside atoms. Food, fuels and electric batteries are stores of

Chemical energy

.

• Anything that is squashed, stretched or twisted stores E

lastic potential energy

. • An object in a high position stores energy as

Gravitational potential energy

.

Energy transfers

• Machines transfer energy between different forms. • An mp3 player transfers stored chemical energy into electrical energy and sound energy.

• Sometimes more than one transfer is involved. The engine of a car transfers chemical energy in the petrol into kinetic energy (useful) and heat and sound (not useful and called

wasted energy

).

• Click (select no option)

Q) Label the useful and the wasted energy

Conservation of energy

• Energy cannot be created or destroyed, it can only be transferred usefully, stored or wasted (called dissipated). • THE TOTAL AMOUNT OF ENERGY DOES NOT CHANGE.

• This is called the

principle of conservation of energy.

Spreading out

• If you look at an energy transfer it can often seem as if some of the energy has ‘disappeared’.

• For example, a car uses chemical energy stored in its fuel.

• The fuel stores a lot of energy in a small space. This chemical energy is eventually transferred by heating into the surroundings, which become warmer. This dissipated energy is very difficult to use for further energy transfers.

Questions

 What are the energy transfers of a torch?

 You are running in sports day. What forms of energy are you transferring that are A) useful and B) wasted?

 A car uses a litre of petrol when it is driven to the shops and back. What happens to the chemical energy that was stored in the petrol?

  What are the forms of energy produced in a Bunsen burner?

If energy cannot be destroyed, how can we ‘waste’ energy?

 Draw a flow chart to show all the energy transfers in a wind-up torch, starting with food. Show how energy is wasted at each stage.