Energy Transferred by Working
Energy and Thermal Physics

When are fuels used?

Teaching Guidance for 11-14 Supporting Physics Teaching

Burning fuel

Wrong Track: To make anything happen you have to burn a fuel like food or petrol.

Right Lines: Some changes happen without a fuel burning.

Using fuels as an introduction

Thinking about the teaching

We suggest starting with fuels because of their obvious usefulness, and because something is very clearly used up. However, thinking about fuels is only an introductory stage on the way to a full appreciation of energy stores, so it is not worth pupils spending too long on this section. Thinking about fuels also provides a useful link to a discussion of energy resources, which follows in episode 03.

For now, and particularly if pupils show signs of claiming that every change needs a fuel, you need a supply of examples where fuels are not needed. Here are some pairs that may be useful:

  • Holding a book up using a shelf as opposed to a human supporting the same book on their hand (your muscle fibres need to keep on contracting and relaxing, so depleting their supply of ATP).
  • An ice skater gliding along the ice as opposed to a car rushing along the motorway.
  • A planet moving around the Sun as opposed to a fairground ride moving around and around.

We hope you spotted that burning fuel enables the second one of each pair, but not the first.

Energy Transferred by Working
appears in the relation dU=dQ+dW
is used in analyses relating to Working Engines Thermionic Emission
is a special case of Work
has the special case Potential Energy Kinetic Energy
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