Bringing together two sets of constraints

Focusing on the learners:

Distinguishing–eliciting–connecting. How to:

• draw on everyday conversations about energy
• build on concerns about energy supply
• formalising the discourse about energy by connecting it to calculations

Teacher Tip: These are all related to findings about children's ideas from research. The teaching activities will provide some suggestions. So will colleagues, near and far.

Focusing on the physics:

Representing–noticing–recording. How to:

• access values for energy
• emphasise the atemporal facet of energy: it's always stored
• distinguish between the physical descriptions of the lived-in world and the descriptions using the idea of energy
• build in the conservation of energy as an assumption in analysis

Teacher Tip: Connecting what is experienced with what is written and drawn is essential to making sense of the connections between the theoretical world of physics and the lived-in world of the children. Don't forget to exemplify this action.

Energy calculations tell us what can happen

Wrong Track: Energy makes things happen.

Right Lines: Energy calculations tell us which processes are possible and which are not.

Energy is not a physical quantity

Thinking about the teaching

Energy is not some physical property that makes things happen. Rather, it is an interesting quantity, calculated in many different ways, that tells us whether or not particular processes are possible. The amount of energy available in a particular situation limits what is possible. Actually doing the calculations, finding out how much energy is available, comes later, in episode 04.

In this introductory phase, you might find that it is useful to draw an analogy with having a certain amount of cash. The quantity that you have limits what you can do, but does not compel you to do anything. Most importantly, it tells you what is not possible.

Keep it simple, allowing cash transactions only!

Making comparisons

Pupils often become very interested when they learn that the money cost of having their TV or computer on is a lot less that for devices such as the cooker, immersion heater or electric fire. Now they can speak with authority when parents complain: No wonder the electricity bill is so huge with you having your computer and television on all the time! However excessive showering may give the parent even more justification for complaint.

Maximum power

Wrong Track: The Rolls-Royce has a power of 338 kilowatt.

Right Lines: The maximum power output for the Rolls-Royce is 338 kilowatt.

Interpreting the figures

Thinking about the teaching

When comparing the power figures of appliances, it is important to stress the point that the figures quoted need to be correctly interpreted. For the Rolls-Royce, 338,000 joule / second is the maximum energy cost per second. The car can, of course, be driven much more carefully so that the energy cost per second is much lower. On the other hand, the power figures for kitchen appliances such as kettles and fridges are likely to be fixed at their normal operating power.

Personal power

One enjoyable lesson you may try involves pupils carrying out a simple activity (such as running up some stairs) to measure their personal power. At the start of this activity it is worth talking through whether or not pupils are aiming to go for their maximum power or to be more relaxed in their approach!

There's a good chance you could improve your teaching if you were to:

Try these

• emphasise that energy is essentially quantitative
• talk and act as if energy is a constraint on possibilities, not a cause of a process
• work with a clear ontology
• keeping power and energy separate

Teacher Tip: Work through the Physics Narrative to find these lines of thinking worked out and then look in the Teaching Approaches for some examples of activities.

Avoid these

• allowing an endless list of kinds of energy
• using energy as cause

Teacher Tip: These difficulties are distilled from: the research findings; the practice of well-connected teachers with expertise; issues intrinsic to representing the physics well.