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
Elastic 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
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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?
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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.