Energy: a common currency
Physics Narrative for 11-14
Costing up activities with joules
All of our everyday activities, whether driving to school, doing the washing-up, or going for a walk, have a cost. The cost we are thinking about here is not one of money, but one of energy. In fact, energy provides a common currency that allows us to count the relative cost of all of these different kinds of activity.
The comparisons are made in joule (J), which is the unit of energy. Just as we can look at the prices of new goods or services that we might want to buy, so can we check out the energy costs of different processes and activities. If we don't have access to sufficient energy, this rules out the possibility of doing whatever it is we might want to do.
When counting energy costs the numbers are often large, so we use larger chunks of the currency, grouping the joules into thousands to give kilojoule (kJ). Quantifying processes in terms of energy in one of the fundamental methods of problem solving in science.