Christmas decoration convection and the new energy

 

We made rotating foil spirals and tried to figure out how to describe what was going on using the "new" energy descriptions for English schools. This vocabulary is based on the First Law of Thermodynamics so involves talking about heat or work crossing a system boundary. They have also made the vocabulary easier to digest by splitting heat into "heating by particles" and "heating by radiation. Work is similarly split into "mechanical working" and "electrical working". So energy flows from the candle into the air by the "heating by particles" pathway. The internal energy of the air increases. The extra k.e. makes means that the particles move further apart. This expansion and subsequent rise of the less dense gas will be via the "mechanical working" pathway. There are a lot of arguments about this and major holes to be picked in what I've just described. It was easier just to call it convection but I'm optimistic that the approach will give students a better handle on thermodynamics.