FACT SHEET
Energy transfer to surroundings
USEFUL AND WASTED ENERGY
NO
FACTS
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.
