© boardworks ltd 20061 of 35 many household objects are designed to transfer energy from one form...
TRANSCRIPT
© Boardworks Ltd 20061 of 35
Many household objects are designed to transfer energy from one form into another useful form.
What is a useful energy transfer?
electricalenergy
kineticenergy
What energy transfer is an electric fan designed to carry out?
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20062 of 35
electricalenergy
soundenergy
What energy transfer are these speakers designed to carry out?
What is a useful energy transfer?
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20063 of 35
What energy transfer are wind turbines in a wind farmdesigned to carry out?
What is a useful energy transfer?
kineticenergy
electricalenergy
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
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gravitationalpotential energy
electricalenergy
What energy transfer is a hydroelectric power station designed to carry out?
What is a useful energy transfer?
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20065 of 35
electrical
light
sound
heat
An energy transfer diagram shows the input and output energies for a device. This includes all the useful and wasted forms of energy.
Energy transfer in a television
For example, in a television:
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20066 of 35
electricalsound
heat
What are the main energy transfers in a radio?
(Don’t forget the wasted energy.)
Energy transfer in a radio
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20067 of 35
chemical
kinetic
sound
heat
What are the main energy transfers in a car engine?
(Don’t forget the wasted energy.)
Energy transfer in a car engine
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
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All the energy transfers (useful and wasted) that are associated with a device can be represented by a Sankey diagram.
A Sankey diagram uses arrows to represent all the output energies.
How can we represent energy transfers?
100 Jelectrical
energy(input)
20 Jelectrical
energy(input)
10 Jlightenergy(output)10 J
heat energy(wasted)
90 Jheat energy
(wasted)
10 Jlightenergy(output)
Energy efficient light bulb
Filament light bulb
How does the energy use in these light bulbs compare?
The thickness of each arrow is proportional to the amount of energy involved at that stage.
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
© Boardworks Ltd 20069 of 35
This cordless drill transfers chemical energy in the battery into movement, sound and heat energy.
Appliances usually waste energy as sound and heat.
How is energy wasted?
The movement energy can be used to do useful work, but the sound and heat energy cannot.
Energy that does not do useful work is called wasted energy.
In fact, all electrical devices produce a small amount of heat energy when they are used, which is normally wasted.
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
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If a device makes noise but is not designed to make noise, then energy is being wasted as sound.
Examples of devices that waste energy as sound include:
Which devices waste energy as sound?
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
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If a device gets warm but it is not designed to get warm, then energy is wasted as heat.
Examples of devices that waste energy as heat include:
Which devices waste energy as heat?
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.
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Remember that energy cannot be created or destroyed.
What happens to the wasted energy produced when energy is changed from one form to another?
What happens to wasted energy?
For example, the heat and light energy produced by this light bulbare too spread out to be reused.
Wasted energy spreads out into the surroundings – this is called dissipated energy.
This dissipated energy is too spread out to do useful work and so cannot be reused.
Describe energy transfers, showing an awareness of conservation of energy.Spell keywords correctly.