Filament light bulbs versus energy-saving light bulbs If we take the example of the old-type filament light bulbs compared to the modern energy- saving light bulbs, we can see that the filament bulbs are 10% efficient whereas the energy saving bulbs are 75% efficient.
Example 2 Car engine A car engine uses chemical energy in the form of petrol or diesel. This is converted to motion energy, but much is dissipated as heat and sound energy.
Energy input 1000 J chemical energy Energy output
400 J useful motion energy 450 J dissipated heat energy 150 J dissipated sound energy
Motion energy 400J
Input energy
Efficiency: 400 J x 100 = 40% efficiency 1000 J
Chemical energy 1000J Sound energy 150J
Dissipated sound energy
Heat
energy 450J
Dissipated heat energy
92% to 100% 81% to 91% 69% to 80% 55% to 68% 39% to 54% 21% to 38% 1% to 20%
330
Fig. 15 The energy efficiency of an appliance is displayed on a special label.
Useful output energy
The energy efficiency of an appliance is displayed on a special label. An appliance with an energy efficiency rating A is the most efficient.
