Maybe Swackhamer was right after all...

Here is an episode in which a teacher struggles to understand what exactly is meant by “electromagnetic energy.” What I observe in this episode is that this teacher has learned a lot of names of “forms” of energy, but doesn’t really have a physical picture of what these forms mean. He is trying to build that physical picture, but is really struggling.

I think this is exactly the kind of thing Swackhamer is complaining about when he says that the idea of “form” is meaningless. I argued in this post that the idea of form is useful as a shorthand for the description of what is physically happening in the system. But if form is just a label and there is no physical picture behind it, it is indeed meaningless. This is yet another example of people mistaking the representation for the thing it represents, like manipulating equations without realizing that they are just representations.

I was discussing this with Eleanor at lunch yesterday and she pointed me to the following national standards for what students should learn about energy:

• Energy appears in different forms and can be transformed within a system. Motion energy is associated with the speed of an object. Thermal energy is associated with the temperature of an object. Gravitational energy is associated with the height of an object above a reference point. Elastic energy is associated with the stretching or compressing of an elastic object. Chemical energy is associated with the composition of a substance. Electrical energy is associated with an electric current in a circuit. Light energy is associated with the frequency of electromagnetic waves. 4E/M4*
• Chemical energy is associated with the configuration of atoms in molecules that make up a substance. Some changes of configuration require a net input of energy whereas others cause a net release. 4E/H4*

I’m glad there are standards addressing the physical meaning of different forms of energy, but I don’t think the phrase “is associated with” is specific enough. I think these sentences ought to read more like, “Motion energy means that an object has speed. Thermal energy means that the molecules of an object are moving (and more motion means higher temperature). Gravitational energy means that object is separated from the Earth.” Etc.

Maybe we need to add something to the Energy Theater worksheet that explicitly addresses this. Something like: “Describe what physical thing is represented by each of the types of energy in your scenario.”

I’m sure that somehow I could write a paper about this issue.