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This fact sheet provides information on the input and output energy of various appliances, distinguishing between useful and wasted energy. Examples include hairdryers, computers, cars, and coal-fired power stations. The document also includes a flow diagram and a sankey diagram to illustrate the energy transfer.
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1 Input energy – The amount of energy needed to operate a device. 2 Output energy – The energy, power, or work produced by a system. 3 Useful output energy – Amount of useful energy produced by a device. 4 Wasted energy – Amount of energy that is not used for the required output, converted to another form of energy (heat, sound or light). 5 Systems such as appliances, tools, vehicles and machines provide useful energy outputs. 6 Some energy that is transferred in a system can escape to the surroundings as wasted energy in the form of heat, light or sound which is produced by the energy system, but not considered as useful. 7 Hairdryers are used because they produce heat, but the sound it makes, is wasted energy which cannot be used. 8 Computers are useful machines, but the heat energy produced, is wasted energy. 9 Energy systems always give out less useful energy than the amount of energy that was put in. 10 Cars can waste up to 65% of the energy that they get from petrol/diesel. 11 Almost 50% of the energy released from burning coals of a coal-fired power station, is wasted as heat energy. 12 Up to 10% of the electrical input energy is transferred into light energy when using an incandescent light bulb. The filament of the light bulb produces mostly heat energy. 13 It is advisable to rather use compact fluorescent lamps, because they need less electricity as input and they convert approximately 30% of the input energy into heat energy. 14 Sounds of electric appliances [e.g. food processor; lawn mower; hairdryer; etc.] are energy wasted. 15 In the flow diagram below it is noticeable that the output energy arrow is smaller than the input energy arrow. Reason? Some of the input energy was wasted.
16. FLOW DIAGRAM of an electric drill that shows the energy transfer when it is used:
Input Output
APPLIANCE ENERGY INPUT ENERGY OUTPUT
USEFUL ENERGY WASTED ENERGY
Television 500 J electrical energy
400 J energy [light]
50 J energy [sound]
50 J energy [heat]
Electric drill 400 J electrical energy
300 J energy [kinetic] 70 J energy [heat] 30 J energy [sound]
Hairdryer 350 J electrical energy
150 J energy [kinetic]
1 50 J energy [heat]
50 J energy sound]
Electrical energy
System Kinetic energy turns the drill
Heat e
nergy
Sound e
nergy
Wasted e
nergy