Key ideas

• When energy transfer happens, there is usually at least partial dissipation.
• Dissipation is a spread of energy into the surroundings. Dissipated energy is less useful.
• We can use energy transfer arrows to indicate the relative amounts of energy that are transferred usefully and that are dissipated in any process.
• Efficiency is a measure of the proportion of energy that is transmitted usefully.

Practical Activity

The practical activity uses the SEP Energy Transfer Kit, or suitable substitute items, to consider energy flow and dissipation along a chain of components.

Visualising the ideas

The animations use energy transfer arrows to explore ideas about dissipation and thereby about conservation.

Click to see animation

Notes and Principles

A key message of booklets 10 to 12 can be summarized by the following diagrams.

a. Energy can transfer directly from store to store, or other energy transfer devices may be involved.

b. Energy can transfer from store partially to a new store and partially to dissipation. Again, there may or may not be intermediate transfer devices. Where there are, they may be responsible for some dissipation.

c. Energy can transfer from store fully to dissipation.