What's so good about the idea of shifting energy between stores?
Physics Narrative for 11-14
The energy story that we are presenting here is rather different from the kinds of approaches that are commonly used in school. As such it is quite instructive to take a specific process and describe it in both the
commonly used and
energy store ways. Let's take lifting a book onto a shelf as the process.
Commonly used approach
Everyman: when I lift the book onto the shelf, chemical energy is transferred from my arm to potential gravitational energy in the book.
We suggest this approach:
Teacher: When I lift the book onto the shelf, energy is shifted from the chemical store of my arm to the gravitational store of the book.
The first approach refers to two kinds of energy, and the picture that is painted is of something tangible (chemical energy) leaving the arm and turning up in the book as something different (gravitational potential energy). There is a confusion and running-together of the physical description with the energy description, with chemical energy being portrayed as something physical that resides in the arm and gravitational potential energy as being something in the book.
The second approach refers simply to
energy moving from one store to another. We like this because we see energy as identical, wherever it turns up it's still the same thing. Energy is a unified abstract idea and it does not make sense to talk about different kinds or forms of energy. In addition, energy is described as being shifted between energy stores. This approach keeps all of the theoretical ideas together in the energy description and does not confuse them with tangible things in the physical world.