4.5 Describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship, including their representation by Sankey diagrams

Everything uses energy. However, energy is often wasted, most commonly as heat. The more useful energy an object/organism outputs, the more efficient it is.

For example, a television [TV] is meant to transfer (not produce!!) electrical energy to light and sound energy. However, (especially in older models) some of this energy is wasted as heat.

Figure 1      ↑

This information can be represented as a Sankey diagram (figure 1). To draw a sankey diagram, you must make sure the arrows are proportional: if the useful output is 100J and the wasted energy is 50 J, the wasted energy arrow should be about half as big as the useful output arrow.

The left part (where in Figure one is says 250 J) is always the energy input. 

The right part is where useful energy comes "out" of.

The bottom (where it says 50J) is wasted energy. Note that wasted energy is not lost, it is transferred to other forms that are not useful.